Class 10 Biology

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction

What is sexual reproduction? What is the significance of this process?

Sexual reproduction is a mode of multiplication or formation of young ones through the process of formation and fusion of gametes. The fusing gametes generally come from different parents so sexual reproduction in most animals is biparental. It is well known that a bull is unable to produce a calf alone and a hen is unable to produce chicken without the other sex.

However, biology being a science of exceptions many lower animals and the majority of plants have both sexes in the same individual. Even then everywhere in sexual reproduction two types of gametes come together and fuse to form a zygote that forms the new individual.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Why The Sexual Mode Of Reproduction

Variations are important in the adaptability of organisms to the changing environment and in the struggle for existence. Some variations appear in asexual reproduction due to errors in DNA copying. However, these errors are either minor or drastic. The latter often kills the cells. Therefore, only minor variations are found in asexually reproduced organisms.

However, in this vast sea of life, individuals must have many variable variations. In sexual reproduction, there is an accumulation of a good number of useful variations that come from different individuals involved in this reproduction. Further, there is a reshuffling of variations due to the reshuffling of genetic materials or chromosomes during their separation and crossing over in meiosis and chance combination during fertilization along with the appearance of mutations during DNA copying.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Basic Features Of Sexual Reproduction

1. Parents:

In most animals and some plants, there are two types of parents, male and female. Such organisms are called unisexual and their sexual reproduction is called biparental. In plants, the two types of sex organs may occur in different flowers of the same plant. They are called monoecious,

For example: Cucurbits, Maize, Castor

In others, the two sexes are borne in flowers of different plants

For example:  Date Palm, Papaya. They are called dioecious.

In most plants and some animals (Sponges, Tapeworm, Earthworm) both sexes are present in the same parent. They are called hermaphrodites or bisexuals.

2. Meiosis:

Gametes are always haploid. They are formed through meiosis.

3. Gametes:

In lower organisms, the gametes are often similar (isogamous). In higher animals and plants there are two types of gametes (anisogamous, oogamous), motile male or sperm and nonmotile female or eggs. The female gametes are often food-laden to provide nourishment to growing embryos.

4. Fertilization

It involves the fusion of two types of haploid gametes. Fusion of gametes or fertilization recreates the diploid state in the life cycle by forming a zygote.

5. New Organism:

The single-celled diploid zygote undergoes repeated mitotic divisions to form the young individual

Sexual Reproduction:

Merits of Sexual Reproduction

• Flow of Genes:  There is a broad resemblance in the morphology and physiology of all the individuals of a population due to the flow or intermixing of genes during sexual reproduction.
• Vigour and Vitality: Reshuffling or flow of genes in the population during sexual reproduction helps in maintaining the vigor and vitality of the individuals
• Variations:  Sexual reproduction introduces a lot of variations due to the reshuffling of paternal and matcha chromosomes, crossing over, chance combination of chromosomes during fertilization, and appearance of mutations. Variations are basic to competitiveness among individuals.
• Adaptability: Sexual reproduction provides variations that help individuals to adapt to changing environments.
• Chromosome Number:  It maintains the chromosome number of the species constant generation after generation.
• Harmful Traits: They often remain suppressed in sexual reproduction due to the occurrence of dominant normal traits.
• Evolution:  Some of the variations in accumulation play an important part in the formation of new varieties and species.

Differences between Asexual and Sexual Reproduction:

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Flowering Plants

What is the flower? How is it unisexual or bisexual?

In flowering plants or angiosperms, the reproductive organs are located in flowers. Flowers are specialized condensed shoots which are also called reproductive shoots as they take part in sexual reproduction. Each flower is borne on a stalk named pedicel.

The pedicel leads to a broad base of the flower called the thalamus. Four types of floral organs are borne over the thalamus. They are sepals, petals, stamens, and carpels (or pistils). Stamens and carpels ( pistils) are essential floral organs that are born over the thalamus

They take part in sexual reproduction. Sepals and petals arc accessory or non-essential floral organs A flower having both stamens and carpels is called bisexual,

Example: Mustard, Hibiscus.

A flower having only one type of reproductive organ is known as unisexual. It is of two types, staminate or male and pistillate or female. In dioecious species male and female flowers occur on different plants,

Example:  Date Palm, Papaya.

In monoecious species, both male and female flowers occur on the same plant,

Example:  Maize, Castor, Cucurbits.

V.S. Flower:

• Sepals (Calyx): They are flat, green, lowermost floral organs that cover and protect the flower in the bud condition. Later on, they provide support to the remaining floral parts.
• Petals (Corolla): They are flat, colored, and often fragrant floral organs that lie above the sepals. They attract insects for pollination.
• Stamens (Androecium): They constitute the third floral whorl. Stamens are the male reproductive floral organs

Each stamen consists of two parts, a slender stalk or filament and a terminal knob-like fertile part called anther. An anther has two lobes. They are attached by a sterile band called a connective. An anther has four long cylindrical pollen sacs, two in each anther lobe. Yellowish powdery haploid pollen grains develop in the pollen sacs through the meiotic division of diploid microspore mother cells. A mature pollen grain usually comes to have one tube cell and two male gametes.

Parts of stamen:

Carpels (= pistils, Gynoecium). They are the centrally placed female reproductive organs of the flower. Depending upon the number of carpels, the flower is called monocarpellary, bicarpellary or polycarpellary.

• Each carpel or pistil is flask-shaped in outline. It has a basally swollen ovary, a stalk called style, and a terminal pollen-receptive part called a stigma. The ovary contains one or more chambers or loculi.
• Each chamber has a parenchymatous cushion called a placenta.
• On the placenta are borne stalked ovoid structures called ovules. An ovule has one or two coverings called integuments with a terminal pore named a micropyle. Internally it contains a diploid parenchymatous nucellus and an oval haploid female gametophyte called embryo sac.
• The embryo sac is seven-celled and has eight nucleates. There is a three-celled egg apparatus, three antipodal cells, and a large central cell with two polar nuclei. In the egg apparatus, there is one female gamete called egg or oosphere and two helper cells named synergids.

Parts of stamen:

What does happen in pollination? Why it is needed for fertilization and fruit seed formation?

Pollination:

It is the transfer of pollen grains from another to the stigma of the flower. There are two types of pollination-self pollination and cross-pollination. In self-pollination, the pollen grains of a flower arc are transferred to the stigma of either the same or genetically similar flower.

• It is autogamy if pollination is between the anther and stigma of the same flower of the same plant It is geitonogamy if pollination occurs between the anther of one flower and the stigma of another flower of the same plant.
• In cross-pollination (Allogamy, Xenogamy) the pollen grains from the anther of one flower are transferred to the stigma of plant another.
• The transfer of pollen grains is carried out by an external agency like wind, water (both abiotic agencies), insects, birds, bats (all biotic agencies), etc

Pollination:

Differences between Self-Pollination and Cross-Pollination

Fertilization:

It is the process of fusion of male and female gametes. The process is initiated when a pollen grain falls on a compatible stigma. It absorbs water and nourishment.

• The pollen grain forms a tube called a pollen tube. Pollen tube passes through the style, reaches the ovary, and enters an ovule, generally through its micropyle. It carries a tube nucleus and two male gametes.
• The pollen tube enters the embryo sac and bursts open into it to release the two male gametes. One male gamete fuses with oospHefe (=egg) to form a diploid zygote.
• The zygote-later forms the embryo. The second male gamete fuses with the central cell to form a triploid primary endosperm cell. This is called triple fusion as it involves the fusion of three nuclei. Primary endosperm cell produces a nutritive tissue called endosperm.
• Embryo obtains nourishment from endosperm while endosperm obtains nourishment from nucellus and the plant.
• Functioning of both the male gametes in the same ovule of flowering plants is called double fertilization. The endosperm may persist or get consumed by the embryo

Flowering Plant:

Differences between Pollination and Fertilization:

Fate of Floral Organs

Petals, stamens, style, stigma, and sepals shrivel and arc shed. Sepals persist in some cases. Fertilized ovule matures into a seed and ovary matures into a fruit.

Seed and Fruit Formation

How is seed and fruit a result of pollination and fertilization?

After fertilization, the ovule slowly matures into seed while the ovary develops into a fruit. In the beginning, the zygote undergoes divisions. It obtains nourishment from the endosperm and grows to form the embryo.

The food reserve for the future may remain in tire endosperm or get transferred to the embryo. In the latter case, the food is stored in the cotyledons of the embryo. The mature embryo becomes dormant. The integuments of the ovule form tough and impermeable seed coats. The ovary wall forms the pericarp (fruit wall). It may be dry (e.g., Groundnut, Mustard) or fleshy

Example: Tomato, Mango

Advantages of Seed Formation:

• Complete Package: Seed is a complete package for the survival and growth of future plants due to dormancy of embryo, presence of reserve food, and protective seed coats.
• Perennation: Because of their tough seed coats and dormant embryos, seeds can pass through unfavorable seasons without any harm.
• Dispersal: Being small and light, seeds can easily be dispersed to long distances.
•  Food: Seeds are a major item of human food.
• Delayed Germination: Seeds can be stored for months and even years. They will germinate only when provided with suitable conditions.

Activity 1: Study of Seed Structure

Take a few seeds of Bengal Gram. Soak them in excess water overnight. Next day drain out excess water and cover the wet seeds with a wet cloth for a day. Keep the cloth wet from time to time. Remove the cloth and study the seed for external features and internal structure.

External Structure:

The seed is a conical pyriformis outline. It has a pointed curved beak at one end. The other end is broad with a depression in the middle. The depression extends on one side upto the pointed end. This site bears a rhomboid dark patch in the middle. The same is called chalaza.

Ahead ofchalaza, towards the pointed end is an oval scar called f hilum. It is the place where the ovule and then the seed bear a stalk for attachment to the placenta. A fine pore called a micropyle occurs between the hilum and the pointed end. On pressing the seeds a small drop of water can be found to ooze out of it.

Internal Structure:

• Cut the seed lengthwise from the depressed part of the broader side towards the pointed end carefully and slowly. Open the seed without breaking it into parts.
• Find out that the seed is covered by two seed coats. The outer is tough and thick testa. The inner is thin and delicate tegmen. The whole interior is occupied by the embryo.
• The embryo has a small embryo axis. Two large food-laden yellow cotyledons are attached to the middle of the embryo axis using short stalks.
• The micropylar end of the embryo axis bears a radicle. The other end bears plumule.
• The radicle is the future root of the plant. Plumule is the future shoot of the plant. It possesses small leaf primordia. The area of the embryo axis between the origin of cotyledons and plumule is called epicotyl.
• The area of the embryo axis between the origin of cotyledons and the radicle is called hypocotyl. Gram seed is dicotyledonous and non-endospermic (= exalbuminous).

Seed Germination

Under favorable conditions, of growth (moisture, aeration, and temperature) the seed absorbs water and swells up. c embryo becomes active. Stored food is mobilized and transferred to the tips of the embryo axis. Radicle is the first to grow. breaks the seed coat and passes into the soil to form the root system. On growth, the activated plumule comes out of the soil and forms the shoot system. This converts the germinating seed into a seedling.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Human Beings

What is puberty? Why do growth and sexual maturity take a long time to complete?

Human beings reproduce only sexually. They are unisexual or dimorphic with the distinction of male and female sexes. The distinction becomes more apparent as the children grow.

• Growth and sexual maturity proceed simultaneously and do take a long time to complete.
• The reason is that the energy and resources of the body are simultaneously being used or the two.
• Puberty is the process of physical changes by which young persons reach maturity and become adults. It begins at the age of 10 to 14 years in girls and 13 to 15 years in boys.
• At this time the primary sex organs become functional but the secondary sex organs are yet to mature.
• Another term used along with puberty is adolescence. Adolescence is a period of psychological and social transition between childhood and adulthood.
• The period of puberty or adolescence is 10 to 20 years. The changes are initially slow but often become rapid later on.
• However, there is no similarity and uniformity in development patterns and speed of changes in different individuals. It is because the changes that occur during this period are partly due to physical growth and partly due to the effect of hormones produced by primary sex organs.

Some of these changes are similar in boys and girls while others are different in the two.

Similar Changes in Girls and Boys:

1. Thick Hair: There is growth of thick hair in the genital area and in the armpits. 
2. Thin Hair: Thin hair appears all over the legs, arms, and face.
3. Genital Area: It often becomes darker.
4. Oil: Skin becomes oily. It results in the development of acne and pimples mostly over the face.
5. Body Awareness: The children slowly become aware of changes in the body as well as changes in the body of others.

Different Changes in Boys:

1. Facial Hair: Moustaches and beards appear.
2. Cracking Voice: The voice becomes low-pitched and cracking.
3. Adam’s Apple:  The larynx grows to form Adam’s Apple.
4. Shoulders: They become broad
5. Pelvis:  The pelvis remains narrow. It becomes strong.
6. Musculature:  Skin thickens, the body becomes muscular and bones become strong.
7. Enlargement: Enlargement of sex organs and occasional activation of the penis.

Different Changes in Girls:

1. Breasts: They become enlarged. Skin becomes dark below the nipples.
2. Menstruation: After its beginning or menarche in early puberty, it becomes regular.
3. Voice:  It becomes high-pitched.
4. Pelvis:  It becomes broad.
5. Skin:  It remains thin. The vasculature is more so that there is increased warmth of the skin.
6. Fat: It gets deposited over the buttocks, thigh, and face.
7. Contours: Body contours round off.
8. Enlargement: There is an enlargement of sex organs (ovaries, fallopian tubes, vagina, uterus) and labia.

Why Does Reproductive Maturity Appear Late: 

The general growth of the body has priority over sexual maturity. Therefore, as the individual is growing, there is slower development of sex organs

• Only after the completion of body growth, the resources of the body are diverted for sexual maturity. The male must develop the ability to develop millions of sperms as a single ejaculation consumes up to 400 million sperms.
• The glands should also become active to form the fluid part of the semen.
• The penis must be able to become erect. Similarly, in females the genital tract becomes mature. The uterus carries the baby for a long period and nourishes the same. The mother provides milk to the neonate for nourishment an event after parturition.

Primary and Secondary Sex Organs

Primary sex organs are those sex organs that give rise to gametes. They are the gonads, and testes in males and ovaries in females. Testes produce sperm and the hormone testosterone. Ovaries produce ova and hormones estrogen and

Secondary sex organs are those organs, glands, and ducts which do not form gametes and hormones but are essential for sexual reproduction because they conduct and nourish the gametes, e.g„ vasa deferentia, prostate gland, penis, uterus, vagina, mammary glands.

Sex Organs and Sex Characters:

Sex organs arc organs that produce, nourish, and conduct Sex cells. Sex characters arc traits that distinguish a male from a female,

Example: Beard in males and clean face in females. are

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Male Reproductive System

It is a system of organs that produce sperm and take the latter near the site of fertilization. The various components of the male reproductive system are testes (a pair), vasa efferentia (12-14 pairs), epididymis (a pair), vasa deferentia (a pair), seminal vesicles (a pair), urinogenital duct, prostate gland, Cowper’s gland (a pair) and penis.

1. Testes (Singular Testis: 

• They are a pair of oval primary male sex organs or gonads. They lie outside the body in a two-chambered pouch of loose skin called scrotum. Scrotum lies behind the penis in between the two thighs.
• The scrotum maintains a slightly lower temperature (34°-35°C) than that of the body (37°C).
• It is required for the formation of viable sperms. A testis has 200-300 lobules with each lobule having 1-3 seminiferous tubules embedded in a connective tissue.
• Connective tissue has Lcydiÿ, cells that secrete the male sex hormone testosterone. Testosterone regulates spermatogenesis and expression of male sex characters. Seminiferous tubules produce sperm.

2. Vasa Efferentia:

They are 12-14 pairs of fine tubules that drain out freshly formed sperms using current created by their ciliated cells.

3. Epididymcs (singular Epididymis):

They are two 4-6 m long tubes that lie coiled and compacted along the base, side, and head of the testes. They store and nourish the sperm for several days. The unejaculated sperms degenerate and are reabsorbed ultimately.

4. Vasa Deferentia (singular Vas Deferens):

They are a pair of 30-35 cm long muscular tubes. Each vas deferens arises from the epididymis, comes out of the scrotum through the inguinal canal, and enters the abdomen.

• It receives a duct from the seminal vesicle and forms an ejaculatory duct.
• In the interior of the prostate gland, the two ejaculatory ducts join the urethra to form the urinogenital duct.
• The urinogenital duct receives the secretion from the prostate gland and the Cowper’s glands.
• It then passes into the penis to open at its tip.

5. Seminal Vesicles:

They are pairs of lobulated racemose glands present between the urinary bladder and rectum. They produce a viscous alkaline secretion rich in fructose, proteins, prostaglandins, and fibrinogen. The secretion forms 60-70% of total seminal plasma.

6. Prostate Gland:

It is a large pyramidal gland that lies in the area of the union of the urethra and ejaculatory ducts. It opens into the urinogenital duct by some 3040 tubules. The secretion is alkaline, viscous, and milky. The secretion is essential for the motility of sperm. It constitutes 20-30% of semen plasma. Muscles of the prostate gland provide the force for ejaculation.

7. Bulbourethral or Cowper’s Glands:

They are a pair of small glands that open into the urinogenital duct separately. Their secretion is alkaline and rich in mucus. It lubricates the genital tract as well as neutralizes the acidity

8. Penis:

It is an erectile male copulatory organ. Its tip is broad and sensitive. The same is called Glans. 

It is covered by a fold of skin called prepuce. The prepuce is removed in many cases by circumcision. Internally penis contains three columns of spongy tissues which get filled with blood at the time of resection. The urinogenital duct (= urethra) passes through one of the spongy columns and opens at tip of the glans Semen

• Semen: It is milky white alkaline sperm containing viscous fluid that is passed out by males during orgasm. The amount is 2.54.0 mL.
• It contains 300 – 400 million sperms: Semen contains fructose (found in humans only in semen), fibrinogen, prostaglandins, and alkaline chemicals.

Sperms:

They are male gametes. Each male gamete is dart-like with three parts—

1. Head: The Head has an acrosome for penetrating the egg coverings, nucleus, and proximal centriole.
2. Middle piece: The middle piece has mitochondria and a distal centriole. It provides energy to the tail for movement.
3. Tail: The tail is a long and narrow vibratile part of the sperm.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Female Reproductive System

It is a system of organs that forms an egg periodically and helps in its fertilization and growth of fertilized egg into a fetus. The female reproductive system consists of a pair of ovaries, a pair of oviducts, a uterus, a vagina, external genitalia, a pair of Bartholin’s glands, and mammary glands.

1. Ovaries:

They are a pair of almond-shaped lobulated female gonads which lie near the kidneys.

• They contain a very large number of immature eggs even when the female child is just born.
• After puberty, one ovum matures alternately in the two ovaries at intervals of 28 days.
• The complex structure in which the ovum matures is called the Graafian follicle.
• Besides forming ova, the ovaries secrete two types of hormones, estrogen for maintaining the female traits and progesterone for the development of the uterine lining or endometrium.

2. Oviducts or Fallopian Ducts:

They are 10-12 cm long curved tubes having ciliated epithelium. They open distally into the uterus.

• Proximally each oviduct has a fimbriated funnel-shaped end called an infundibulum. The pore of the infundibulum is called ostium.
• It lies near the ovary. The oviduct or fallopian duct is slightly swollen behind the infundibulum.
• It is called ampulla. The narrow part behind the ampulla is called the isthmus. Fertilization generally occurs in the junctional area of the ampulla and isthmus

3. Uterus:

It is an inverted pyriform elastic bag. The uterus retains and nourishes the fetus at the time of pregnancy. The empty uterus is 8 cm long, 5 cm broad, and 2 cm thick.

During pregnancy, it enlarges to reach up to the epigastrial region. The lining of the uterus called endometrium is vascular and glandular. The lower tapering part of the uterus is called the cervix. It opens into the vagina.

4. Vagina:

It is a muscular distensible tube of 8-9 cm length. The vagina lies between the cervix and the vaginal orifice present externally. The vagina is the female copulatory organ. It is also a passageway for menstrual flow and the birth canal at the time of parturition.

5. External Genitalia:

A depression called vulva occurs around and above the vaginal orifice. The upper end of the vulva bears a urethral opening. Above it is present a pea-shaped sensitive outgrowth called the clitoris. It is considered to be homologous with a penis by some.

External genitalia consists of two pairs of fleshy folds or labia. The outer folds are larger, thicker, and hairy. They are called labia majora. The inner folds are smaller and nonhairy. They are named labia minora. Both the labia possess sebaceous glands.

6. Bartholin’s Glands:

They are a pair of small glands which occur lateral to the vaginal orifice but inner to the labia minora. The secretion of these glands is alkaline, thick, and rich in mucus. It lubricates the vagina as well as neutralizes its acidity.

7. Breasts:

They are a pair of near-rounded prominences present in the thoracic region of females. They grow during puberty but become active after childbirth. Each breast has a multiporous nipple. The base of the nipple is sensitive and pigmented. It is called areola. Internally each breast has 15-25 lobules having several milk-secreting alveoli embedded in fatty tissue.

Fertilization And Pregnancy

What is fertilization? When is a woman called pregnant?

Human females have a fertility phase of 2-3 days, commonly between 14-16 days of menstrual cycle.

• Coitus during this period will first deposit a large number of sperm in the vagina.
• The sperms then travel to all parts of the female reproductive tract partly by movement of the female reproductive tract and partly by mobility of sperms.
• Fertilization generally occurs in the junctional area of the ampulla and isthmus part of the fallopian tube. Only one sperm enters an ovum.
• The fertilized ovum undergoes cleavage. It first forms a solid ball of cells called a morula. The latter begins to descend the fallopian tube. Meanwhile, the momma gets transformed into a hollow structure called a blastocyst.
• By about the 7th day after fertilization, tfterWastocyst after reaching items, gets attached to its endometrium.
• The fixation of the blastocyst in the wall of items is called implantation.
• Soon after implantation, the blastocyst begins to produce a hormone called hCG (human chorionic gonadotropin). Its presence in urine indicates pregnancy.

The contact between the young embryo and the uterine wall grows into the placenta. The placenta is a disc-shaped structure formed by the joint activity of the embryo and uterus. It contains finger-like outgrowths called villi from the embryo side. From the mother’s side are present blood spaces around the villi. There is thus a large surface area for the exchange of materials. Glucose, amino acids, oxygen, and other biochemicals required by the embryo pass from the mother’s side to the embryo. Wastes of embryos pass in the reverse direction.

Development of fetus inside the uterus of the mother takes about 270 days. It is called the gestation period. After adding 10 days since the previous menstruation the period is considered to be 280 days or 40 weeks. A fully developed fetus and its placenta send out signals for parturition in the form of a fetus’s ejection reflex. The pituitary gland releases oxytocin that brings about uterine contractions. They first push the head of the baby towards the cervix and then push the baby out of the birth canal. Delivery of the baby is followed by the expulsion of the placenta. It is called after birth or decidua.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction What Happens When The Egg Is Not Fertilized

If the egg is not fertilized, it remains alive for one day and then begins to degenerate and descend into the uterus. The uterus had previously thick and spongy endometrium for receiving the fertilized egg. In its absence, the uterine lining begins to starve. It ultimately breaks down. The broken-down endometrium, mucus, and blood come out of the vagina as menstruation. Menstruation lasts for 2 to 5 days.

In case of nonfertilization, menstruation occurs after every 28 days. It is called the menstrual cycle. The cycle prepares and then dismantles all the preparations for rearing a fertilized egg. The first menstruation occurs in the beginning of puberty. It is called menarche. Menstruation stops completely between the age of 45 to 50 years. The permanent stoppage of menstruation in women is called menopause. Temporary stoppage of menstruation also occurs during a period of pregnancy.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Reproductive Health

What is reproductive health? What are contraceptive devices? Name the different types.

It is a state of physical, social, and psychological fitness leading to a safe and responsible reproductive life.

• Sexual maturity occurs only after the completion of growth. However, due to several reasons including curiosity, pressure from friends, and family pressure for early marriage youngsters indulge in sex.
• Such an indulgence is fraught with dangers as unprotected sex can lead to venereal or sexually transmitted diseases (VD, STD) like gonorrhea and syphilis (bacterial infections), warts, and HIV-AIDS (viral infections).
• Pregnancy in the early stages adversely affects the health of the baby as well as that of the mother as the body of the lady is not yet ready to bear the burden of carrying and nourishing a fetus.
• Further, India is a highly populated nation with a high rate of population growth.
• All resources of the country get consumed in trying to meet the basic requirements of the population. Nothing is left for development.
• In a large family, the income of the bread earner is insufficient to provide proper education and upbringing to the children.
• Therefore, there is a need to get married only when a person is fully mature and capable of proper earning.
• There is also a need to prevent some pregnancies and spacing out the birth of the children in such a way that every child can be properly looked after and provided education.
• This is helped by family planning or family welfare departments through centers spread throughout the country. Its emblem of an inverted red triangle is put up on all such centers.
• The assistance provided to couples and women by the centers is free of cost.

The various methods of family planning are called contraceptive devices. They are as follows :

1. Mechanical Methods: They prevent the entry of sperm into the uterus so that chances of conception or pregnancy are avoided.

• Condom:  It is a tubular rubber sheath that is worn over the penis during coitus. Condom also prevents the spread of sexually transmitted or venereal diseases.
• Cervical Cap: It is a rubber nipple that is fitted over the cervix during coitus.
• Vaginal Diaphragm: It is a tubular sheath with a flexible metal ring that is fitted in and over the vagina during coitus.

2. Intrauterine Contraceptive Devices (IUCDs): They are small rubber, plastic, or metallic devices (loop, copper-T) that are fitted in the uterus. IUCDs prevent the passage of sperm into fallopian tubes. However, in some cases, irritation may occur

• Hormonal Methods: They suppress the production of the ovum. The common hormonal method is oral pills. They contain progesterone alone or along with estrogen. i-Pill or T-72 prevents conception even after coitus. Hormonal methods can cause some side effects in some ladies due to disturbance in hormonal balance.
• Safe Period: The fertility period in women is from 14-16 days of menstrual cycle. Adding two to three days on both sides and avoiding sex during this period automatically prevents conception.
• Reversible Sterilization: It is a surgical technique that prevents the passage of sperm into semen in males and ova into fallopian tubes in females.
• Vasectomy: Small pieces of the two vasa deferentia are cut. The cut ends are tied separately.
• Ttibectomy: Small pieces of the two fallopian tubes are cut and the cut ends are tied separately

 Vasectomy:

Tubectomy:

However, surgery has to be performed by skilled persons under completely aseptic conditions. The technique is reversible as the cut ends of vasa deferentia and oviducts can be joined together surgically if a situation requiring pregnancy arises.

Differences between Vasectomy and Tubectomy:

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Long Question And Answers

Question 1.  Answer questions number (A) to (d) based on your understanding of the following paragraph and the related studied concepts. The growing size of the human population is a cause of concern for all people. The rate of birth and death in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body growth is still going on. Some degree of sexual maturation does not necessarily mean that the mind or body is ready for sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of the population.

1. They list two common signs of sexual maturation in boys and girls.
2. What is the result of reckless female foeticide?
3. Wbicb contraceptive method changes the hormonal balance of the body?
4. Write two factors that determine the size of the population.

Answer:

1. Thick hair develops in the genital area and armpits  Skin becomes oily. It results in the development of acne and pimples, mostly over the face.
2. Decline in sex ratio, first in children and later in adults as well.
3. Oral contraception pills.
4. Rate of birth (natality) and death (mortality).

Question 2. What is reproduction? What are its two types? Which one of the two confers new characteristics in the offspring and how ?
Answer:

Reproduction:

It is the phenomenon of the formation of new young individuals by the mature individuals of an organism
.
ReproductionTypes:  Two types

1. Asexual and
2. Sexual.

Sexual reproduction confers new characteristics to the offspring.

New Characters: They appear mostly in sexual reproduction because of (/) Reshuffling of variations.

1. Chance separation of chromosomes during gamete formation, (in) Crossing over during meiosis.
2. Chance combination of chromosomes during fertilization, (v) Mutations.

Question 3.

1. Surgical methods can be used to create a block in the reproductive system for contraception purposes. Name such parts where blocks are created in
   1. Males and 
   2. Females.
2. State any two reasons for using contraceptive devices.

Answer:

1. Surgical methods are used to create cuts or blocks in the reproductive system of males and females to prevent the passage of gametes reaching the site of fertilization. Blocks are created in

1. Vasa deferentia in males
2. Oviducts in females.

2. Contraceptive devices are used to

1. Limit the size of the family so that the resources of the family are not stretched,
2. Spacing the birth of the children to provide attention to every child and take care of the health of the mother.

Question 4. Differentiate between

1. Asexual and sexual reproduction
2. Self and cross-pollination.

Answer:

1. Asexual and Sexual Reproduction:

Asexual reproduction is uniparental where an organism is formed from a somatic propagule of the parent without formation and fusion of gametes. Sexual reproduction is biparental involving the formation and fusion of gametes during the formation of offspring.

2. Self-pollination:

Self-pollination is the deposition of pollen grains from the anther to the stigma of the same or genetically similar flower. Cross-pollination is the deposition of pollen grains from the anther of one flower to the stigma of a genetically different flower.

Question 5. In tobacco plants, the male gametes have 24 chromosomes. State the number of chromosomes in

1. Egg nucleus
2. Zygote 
3. Endosperm
4. Leaf cell.

Answer:

Male gamete has a haploid number of chromosomes. It is 24.

1. The egg nucleus also possesses a haploid number of chromosomes. It should be, therefore, 24.
2. Zygote has diploid number of chromosomes. 24 × 2 = 48.
3. Endosperm has a triploid number of chromosomes. 24 ×  3 = 72.
4. Leaf cell also has a diploid number of chromosomes. 24 × 2 = 48.

Question 6.

1. What is the site of implantation and development of young ones in human females?
2. Mention two advantages of using mechanical barriers during sexual acts.

Answer:

1. Site of Implantation and Development of Young One. Uterus.

2. Advantages of Mechanical Barriers:

1.  No spread of sexually transmitted diseases
2.  Prevention of conception.

Question 7. What is the placenta? State its two roles during pregnancy.
Answer:

The placenta is a spongy vascular complex formed by maternal and fetal tissue in the wall of the uterus. Blood vessels
of the two are nearby inside the placenta.

Roles:

• Attachment of fetus.
• Providing nutrients and oxygen to the fetus and removing waste products of the fetus,
• Secretion of hormones for maintaining pregnancy,

Example: hCG.

Question 8.

1. Name the organ which helps in providing nutrition to the embryo. Where is it located?
2. What causes the delivery of a child from the mother’s uterus?

Answer:

1. Organ for Nourishing the Embryo:
   1. Placenta. It is located in the endometrium of the uterus.
   2. The placenta is formed by the joint activity of the embryo (villi part) and endometrium (blood sinuses).
2.  Development of fetal ejection reflex by the fully developed fetus and the placenta that supports it.
   1. It induces the pituitary to release the hormone oxytocin.
   2. Oxytocin produces contractions of the uterus for parturition.

Question 9. List the modes of pollination and define each of them.
Answer:

Pollination or transfer of pollen grains from another to stigma is of two types, self-pollination, and cross-pollination.

Self-Pollination:

It is the passage of pollen grains from the anther to the stigma of either the same or genetically similar flower,

For example:  Commelina.

Cross-Pollination:

It is the passage of pollen grains from the anthers of one flower to the stigma of a genetically different flower,

For example Salvia.

Question 10. Define any three of the following terms used about human reproduction :

1. Fertilization
2. Implantation
3. Placenta
4. Gestation
5. Parturition
6. Ovulation

Answer:

1. Fertilization:  It is the fusion of male and female gametes to form a diploid zygote.
2. Implantation:  It is the attachment of the embryo to the wall of the uterus for fixation, protection, and nourishment.
3. Placenta:  It is a spongy and vascular structure formed in the wall of the uterus by the joint activity of the fetus and uterus for attachment and nourishment of the embryo.
4. Gestation:  It is the period between conception and parturition that is passed by the baby in the body of the mother.
5. Parturition:  It is the process of giving birth to a baby by the mother.
6. Ovulation:  It is the release of the mature ovum by an ovary that occurs about the 13th or 14th day of the menstrual cycle.

Question 11. Explain double fertilization in plants
Answer:

The fusion of both the male gametes brought by pollen tubes with two different cells of the same embryo sac is called double fertilization.

• In double fertilization, one male gamete fuses with an egg to form a diploid zygote. It is called generative fertilization.
• The second male gamete fuses with the central cell having two polar nuclei.
• It forms a triploid primary endosperm cell or PEC. The second act of fusion is called triple fusion (fusion of three haploid nuclei) or vegetative fertilization.
• It gives rise to nutritive tissue endosperm for nourishing the embryo.

Question 12.

1. How many eggs are produced every month by either of the ovaries in a human female? Where does fertilization take place in the female reproductive system?
2. What happens in case of egg released by the ovary is not fertilized?

Answer:

1. Every month only one egg is produced by ovulation from one of the two ovaries. The egg passes into the fallopian tube on its side. Its fertilization occurs in the region of the ampulla-isthmus junction.
2. In case the egg is not fertilized, it loses its viability after about 24 hours. It begins to descend slowly and pass into the uterus. Meanwhile, the corpus luteum begins to degenerate.  In the absence of hormones progesterone and estrogen, the glandular part of the endometrium breaks down. Endometrial pieces along with mucus and some blood is passed out as menstruation. Menstruation lasts for 2-5 days.

Question 13. State a function of each of the following parts of the human male reproductive system :

1. Vas Deferens
2. Testis
3. Prostate gland.

Answer:

1. Vas Deferens: Passage of sperms from the epididymis to the ejaculatory duct in the lower abdomen.

2. Testis: 

1. Formation of sperms
2. Production of male sex hormone called testosterone.

3. Prostate Gland:  Formation of 20 to 30% of semen plasma which is essential for sperm motility. Its muscles help in ejaculation.

Question 14.

1. Name the organ known as the birth canal.
2. Give a reason for blocking fallopian tubes for birth control.
3. Give two possible reasons for adopting contraceptives for

Answer:

1. Vagina
2. Blocking the fallopian tubes will not allow the egg to pass down and the sperm to reach the egg.
3. Contraceptives are used to prevent pregnancy to have
   1. Fewer children
   2. Spacing birth of the children.

Question 15. List four points of significance of reproductive health in society. Name any two areas related to reproductive health that have improved over the past 50 years in our country.
Answer:

1. STDs:

• It protects from catching sexually transmitted diseases.
• Small family norms help proper care and education of the children.
• Less mortality among women and infants.
• Attainment of safe, responsible, and satisfying reproductive life.

2. Improvement:

• Reduction in the rate of population growth.
• People have started preferring small family norms.
• Decrease in the incidence of sexually transmitted diseases.

Question 16. State the basic requirement for sexual reproduction. Write the importance of such reproduction in nature.
Answer:

Basic Requirements :

1. Two parents
2. Meiosis and formation of two types of gametes
3. Fertilization or fusion of two types of gametes to produce a diploid zygote.

Importance:

Sexual reproduction introduces variations and the formation of new characteristics due to chance separation and the chance of coming together of chromosomes and crossing over. It maintains the vigor and vitality of the race. Variations allow individuals to adapt to changing environments and develop fitness for the struggle of existence.

Question 17. List any four steps involved in sexual reproduction and write its two advantages.
Answer:

Steps:

1. Meiosis and formation of two types of gametes
2. Transfer of male gametes
3. Fusion of male and female gametes
4. Formation of diploid zygote
5. Development of zygote into new individual.

Advantages of Sexual Reproduction:

1. Formation of variations and new characteristics
2. Maintenance ofvigour and vitality
3. Adaptability to changes in the environment
4. Evolution is due to the accumulation of variations and mutations.

Question 18. What is carpel? Write the function of its various parts.
Answer:

Carpel:

It is the female reproductive part or floral organ of a flower.

The carpel has three parts:

1. Stigma
2. Style, and
3. Ovary

These are:

1. Stigma:  Pollen receiving part of the carpel.
2. Style: Stalk for lifting the stigma to receive pollen grains conveniently, Passege-way for the pollen tube to reach the ovary.
3. Ovary:  Contains ovules which on fertilization form seeds while the ovary matures into fruit.

Question 19. Distinguish between pollination and fertilization. Mention the site and product of fertilization in a flower
Answer:

Distinguish between pollination and fertilization:

1. Site of Fertilization: Embryo sac in the ovule of an ovary.
2. Product of Fertilization:  Zygote, Primary Endosperm nucleus (flowering plants)

Question 20. 

1. State one drawback of each of the following :
   1. Oral Contraceptive pills 
   2. Copper T.
2. Under which category of contraceptive methods, is the use of condoms kept? In what way its use is better as compared to other methods of contraception?

Answer:

1.

1. Oral Pills –  Disturb the secretory activity of the pituitary, cause hormonal imbalance, and disturb ovulatory menstrual cycles.
2. Copper T –  It may irritate the uterus.

2. Condom is a barrier method of contraception. It prevents the passage of sperm in the genital tract of the female. It also prevents the catching up of sexually transmitted diseases.

Question 21. Give reasons :

1. The placenta is extremely essential for fetal development 
2. The uterine lining becomes thick and spongy after fertilization.
   

Answer:

1. The placenta is the disc-shaped joint structure between the embryo and the uterus. It is essential for fetal development as

1. It provides attachment to the embryo
2. Develops large surface area for transfer of nutrients from mother to embryo and waste substances from embryo to mother.

2. Uterine lining becomes thick and spongy after fertilization for proper attachment and nutrient support to the embryo.

Question 22.

1. In a flower, name the parts where
   1. Pollen grains are produced and 
   2. Pollen grains are transferred.
2. What happens to the ovule and ovary after fertilization?

Answer:

1.

1. Pollen grains are produced inside anthers of stamens
2. They are transferred to the stigma of the pistil.

2. The ovule matures into seed while the ovary gives rise to fruit.

Question 23. Suggest any two contraceptive methods to control the size of the human population and explain them.
Answer:

Contraceptive methods are used to prevent unwanted pregnancies and thus control the size human population.

The two common contraceptive methods are oral pills and condoms:

1. Oral Pills:  They are hormone (progesterone) containing pills taken by women to prevent ovulation and hence pregnancy.
2. Condom:  It is a barrier method, used by men over the penis or women in the vagina that prevents sperm from entering the genital tract of the female

Question 24.

1. What is the function of another? How does the fusion of male and female gametes take place in plants?
2. Name the most effective contraceptive which prevents the spread of sexually transmitted diseases.

Answer:

1. Function of Anther:

It is the male reproductive part of the flower. Anther produces haploid spores called pollen grains. On germination over the stigma, each pollen grain produces a pollen tube containing two male gametes.

Fusion of Male and Female Gametes:

A pollen tube carrying two male gametes passes through style, reaches ovary, and enters an ovule. It penetrates the embryo sac and bursts open to release the two male gametes. One male gamete fuses with the oosphere and forms a diploid zygote or future embryo. It is known as generative fertilization.

The second male gamete fuses with the central cell having two polar nuclei. It produces a triploid primary endosperm cell. This fusion is called vegetative fertilization or triple fusion. The phenomenon of functioning of both the male gametes brought by a pollen tube by fusing with two different structures of the same embryo sac is called double fertilization.

2. Effective Contraceptive against STDs:

Condoms in males and fern shields/Vaginal diaphragm in females.

Question 25.

1. State any three advantages of sexual reproduction over asexual reproduction.
2. Explain what happens to the egg once it gets fertilized in the human female.

Answer:

1. Advantages of Sexual Reproduction over Asexual Reproduction:

• Sexual reproduction produces a large number of variations and new combinations of the traits which is not possible in asexual reproduction.
• It hides the harmful traits,
• Sexual reproduction maintains the vigor and vitality of the race,
• It increases the adaptability and competitiveness of the individuals.

2. Egg After Fertilization:

Soon after fertilization, the egg begins to undergo cleavage. It first forms a solid ball or morula and then a hollow structure called a “Blastocyst”.

• Blastocyst reaches the uterus. It comes in contact with the endometrium and develops finger-like outgrowths called villi.
• Villi corrode the endometrium and fixes the blastocyst. The process is called implantation.
• The contact region grows into a disc-shaped spongy and vascular structure called a placenta.
• The blastocyst develops into a fetus. An umbilical cord develops between the fetus and the placenta. The placenta provides nourishment to the fetus.
• It also takes away the waste products of the fetus. A fetus becomes fully developed in about 270 days after fertilization.
• The period of embryonic development is called the gestation period. The fully developed embryo and its placenta develop the ejection r reflex which induces the pituitary to release oxytocin. Oxytocin causes contractions of the uterus to push the baby through the birth canal.

Question 26. 

1. Categorize the following flowers into bisexual and unisexual: Papaya, Watermelon, Hibiscus,
2. Mustard.
3. State the function of the urethra in man.
4. When does ovulation occur during the menstrual cycle in a normal healthy woman?
5. What is menopause?

Answer:

1. Bisexual:  Hibiscus, Mustard.

Unisexual:  Papaya, Watermelon.

2. Function of Urethra:

It is the pathway for the elimination of urine in both human males and females. In human males, the urethra is also used for the ejection of semen.

3. Ovulation:

Ovulation or liberation of eggs occurs in human females on the 13th or 14th day of the menstruation cycle.

Menopause:

Menopause It is the permanent cessation of menstruation in women that commonly occurs between the age of 45 to 50 years.

Question 27.

1. How do the following contraceptives prevent pregnancy :
   1. Oral pills
   2. Condom.
2. Mention the possible misuse of surgical methods of birth control by some people. How is this method causing harm to the society? State the steps taken by the government to prevent this misuse.

Answer:

1. 

1. Oral Pills:  They contain progesterone which prevents ovulation and hence pregnancy.
2. Condom: It is a mechanical barrier that does not allow the sperm to enter the reproductive tract of the female.

2. Misuse ofSurgical Method:

Unwanted pregnancy was previously terminated surgically. It is called abortion. However, as the technique of sex determination became common, abortion was used on a large scale in terminating female fetuses.

• This female foeticide caused a fall in the sex ratio (1000 males to 800 females).
• Such a skewed sex ratio is liable to cause a lot of social tension.
• Therefore, the government has banned the prenatal sex test.
• There is a huge fine and imprisonment for persons indulging in sex determination and female foeticide.

Question 28.

1. Explain what happens when

1. Testosterone is released in males
2. Pollen grain falls on the stigma of the flower
3. Egg fuses with sperm cells.

2. Differentiate between pollen tube and style.

Answer:

1. 

1. Testosterone:  It helps in sperm formation. Puberty changes in boys are due to it. It maintains secondary sexual characters.
2. Pollen Grain:  After falling on a compatible stigma, the pollen grain absorbs water and germinates. It gives rise to a pollen tube. Firstly, stigma and then style provide nutrients for the growth of pollen tubes.
3. Egg Fuses with Sperm Cell:  It produces a diploid zygote. The act of fusion of egg with sperm is called fertilization. The diploid zygote later grows to form an embryo.

2. Pollen Tube and Style:

The pollen tube is part of the male gametophyte which develops from a pollen grain for carrying the male gametes to the ovule. Style is the stalk that is meant for lifting the stigma above the level of the ovary to capture the pollen grains.

Question 29. 

1. Name the organ that produces sperm as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.
2. Give an example of each of the unisexual and bisexual flowers.
3. Differentiate between two types of pollination that occur in flowers.

Answer:

1. Testes: They produce sperm as well as the hormone testosterone.

Functions of Testosterone:

1. Controls the formation of sperm
2. Brings about changes in boys at puberty.
3. It maintains the secondary sexual characteristics in male individuals.

2. Unisexual Flowers:  Cucurbita, Papaya.

Bisexual Flowers: Petunia, Mustard.

3. The two types of pollination are self-pollination and cross-pollination:

Question 30. Write the functions of the following parts in the human female reproductive system :

1. Ovary
2. Oviduct 
3. Uterus

Answer:

1. Ovary:  Formation of ova, secretion of hormones estrogen and progesterone.

2. Oviduct (Fallopian Tube):

1. Collection of ovum
2. Site of fertilization
3. Providing passage to ovum.

3. Uterus:

Attachment to the fetus, protection to the fetus, nourishment, gaseous exchange, and waste disposal of the fetus.

Question 31. Define pollination. Explain the different types of pollination. List two agents of pollination. How does suitable pollination lead to fertilization?
Answer:

Pollination: 

It is the transfer of pollen grains from another to the stigma of a flower.

Types of Pollination:  Two types are

1. Self-pollination and
2. Cross-pollination.

In self pollination pollen grains from the anther of a flower pass to the stigma of the same or genetically similar flower.

In cross-pollination, pollen grains of the anther of a flower are transferred to the stigma of the flower of another (genetically different) plant. Agents. Wind, water, insects, and other animals.

Suitable Pollination:

The compatible pollen grain absorbs water and nutrients from the stigma. It swells up and forms a tube called a pollen tube. Pollen tube comes to have two male gametes. It passes through the style, reaches the ovary, enters an ovule, and pierces the embryo sac. One male gamete fuses with the oosphere to form a zygote while the other fuses with the nucleus of the central cell to form a triploid primary endosperm cell.

Question 32. 

1. Identify the given diagram. Name the parts 1 to 5
2. What is contraception? 

Answer:

1. The female reproductive system.

 Female reproductive system Parts:

1. Fallopian tube/oviduct
2.  Ovary
3. Uterus
4. Cervix.
5. Vagina.

2. Contraception:

It is the prevention of conception or pregnancy. The mechanisms used to prevent pregnancy are called contraceptive devices.

Question 33.  What is sexual reproduction? Explain how this mode of reproduction gives rise to more viable variations than asexual reproduction. How does this affect evolution?  Sexual reproduction is a mode of multiplication in which new individuals develop after the process of formation and fusion of gametes.
Answer:

Sexual reproduction:

Sexual reproduction is a mode of multiplication in which new individuals develop after the process of affirmation and fusion of gametes.

In asexual reproduction, variations do not appear except when there is some wrong incorporation to nucleotides during DNA replication.

In sexual reproduction variations develop due to several reasons: 

• Random separation of chromosomes during gamete formation.
• Random coming together of chromosomes during the process of fertilization
• Changes in chromosomes due to crossing over

Mixing of variations from two different parents and formation of new variations due to crossing over. Sexual reproduction maintains the vigor and vitality of the individuals.

Its variations also hide the harmful traits. Therefore, variations produced by sexual reproduction provide adaptability and competitiveness to the individuals. On accumulation, they also produce new species and hence cause evolution.

Question 34.

1. List three different categories of contraception methods.
2. Why has the Government of India prohibited prenatal sex determination by law? State its benefits in the long run.
3. Unsafe sexual acts can lead to various infections. Name two bacterial and two viral infections caused due to unsafe sex.

Answer:

1. Contraception Methods:

1. Barrier or Mechanical Methods,
   • For example:  Condom
2. Intrauterine  Contraceptive Devices
   • For example: Copper T
3. Hormonal methods
   • For example:  Oral pills.

2. Prenatal Sex Determination:

It has been banned due to large-scale female foeticide. The child sex ratio declined.

Benefits:

Benefits It shall restore the sex ratio for a healthy society.

3. Unsafe Sexual Act: 

1. It can result in unwanted pregnancy.
2. It may spread sexually transmitted diseases.

Bacterial STDs:  Syphilis, Gonorrhoea.

Viral STDs:  Warts, HIV-AIDS.

Question 35.

1. What is puberty?

2. Describe in brief the functions of the following parts in the human reproductive system : 

1. Testes
2. Seminal vesicle
3. Vas deferens
4. Urethra.

3. Why are testes located outside the abdominal cavity?

4. State how sperms move towards the female germ cell.

Answer:

1. Puberty:  It is the phase of physical changes by which young persons reach sexual maturity and become adults.

2.

1. Testes:  Formation of sperm and secretion of hormone testosterone.
2. Seminal Vesicle:  Secretion of fluid for nourishing and transport of sperms.
3. Vas Deferens:  Passage of sperms from epididymis to ejaculatory duct in the lower abdomen.
4. Urethra:  In males, common passage for urine and sperm.

3. In order the provide lower temperature for formation and maturation of sperms.

4. With the help of a vibratile tail.

Question 36. . Based on the given diagram answer the questions given below :

1. Label the parts A, B, C and D.
2. Name the hormone secreted by the testis and mention its role.
3. State the functions of B and C in the process of reproduction.

Answer:

1. 

1. A-Ureter
2. B-Seminal vesicle.
3. C-Urethra. D-Vas Deferens.

2. Testosterone: Regulation of sperm formation, appearance and maintenance of male characteristics.

3. The function of B: Its secretion provides nutrition and a medium for the transport of sperm.

4. The function of C: Common passage for urine and sperm.

f

Question 36.  What are the advantages of sexual reproduction over asexual reproduction?
Answer:

• Due to the coming together of variations from the two parents, chromosome separation, crossing over, and t chance combination of chromosomes during fertilization, sexual reproduction produces a large number of variations. This is not possible in asexual reproduction.
• It hides the harmful traits. The same does not occur in asexual reproduction. ;
• Sexual reproduction maintains the vigor and vitality of the individuals. In asexual reproduction, there is a slow deterioration. !
• It increases the adaptability and competitiveness of the individuals. Asexual reproduction does not help in it.

Question 37. What are the functions performed by testis in human beings?
Answer:

Testis has two functions.

1. Formation of Sperms:

The germinal cells present in the lining of seminiferous tubules produce sperms through meiosis. They are nourished by Sertoli cells.

2. Testosterone:

It is male sex hormone that is secreted by Leydig or interstitial cells of the connective tissue of the testis. Testosterone is essential for sperm formation, the development of male sex organs during puberty, and the maintenance of male sex characteristics.

Question 38. What are the different methods of contraception?
Answer:

Contraception methods are devices that when employed prevent conception. They are of the following types :

1. Mechanical Barriers:

They do not allow the sperm to enter the uterus.

• Condoms: Tubular rubber sheaths worn over the penis at the time of coitus
• Cervical Caps:  Rubber nipples fitted over cervix.
• Fern Shields:  They are tubular rubber sheaths with flexible metallic rings which are fitted over and inside the vagina at the time of coitus.

2. Intrauterine Contraceptive Devices (IUCD):

They are plastic and metallic devices that are inserted in the uterus to prevent the escape of sperm into the fallopian tubes. IUCDs destroy or debilitate sperms. Common IUCDs are loops, spirals, shields, and Ts. Copper-T is the most common one. It releases ionized copper to immobilize the sperm.

3. Oral Pills:

They are progesterone-containing pills that are taken by women regularly to prevent ovulation.

4. Chemical Methods:

They are creams and jellies which are applied inside the vagina for the killing of sperm.

5. Reversible Sterilization:

They are surgical methods that block the passage of sperm in males and ova in females

• Vasectomy:  Both the vasa deferentia are cut in the scrotal region and the cut ends are tied.
• Tubectomy:  Both the fallopian tubes are cut midway and the cut ends are tied.

Question 39. How are modes of reproduction different in unicellular and multicellular organisms?

Question 40. How does reproduction help in providing stability to the population of species?
Answer:

In nature, older individuals become senescent and die. The youngsters become adults and the adults become older. Reproduction is regularly adding new young individuals into the population.

This helps the population in

1. Perpetuation of species
2. Maintaining several individuals in the population
3. Stability of the different sections of the population.

Question 41.  What could be the reasons for adopting contraceptive methods?
Answer:

• Controlling the size of the population.
• Enjoying tension-free reproductive health.
• Protection from sexually transmitted diseases.
• Having a smaller economically viable family.
• Better health of the women.
• Spacing the birth of children so that they can be properly looked after, educated, and provided with amenities to grow into good citizens.

Question 42.

1. Which glands contribute fluid to the semen?
2. State two advantages semen offers to sperms.

Answer:

1. Seminal vesicles and prostate gland.

2.

1. Medium of transport
2. Nourishment of sperms
3. Activation of sperms.

Question 43.

1. List two advantages of vegetative propagation.
2. In which of the following plants is vegetative propagation practiced Banana, Rice, Tomato, Rose?

Answer:

1. Vegetative propagation Advantages:

• Vegetative propagation is the only method of multiplication in seedless plants
• Good quality of variety can be maintained indefinitely.

2. Banana, Rose.

Question 44.

• Name one organ in the female and male reproductive system that plays the role of endocrine gland along with the production of germ cells. Name one hormone secreted by each of them.
• State two advantages of the development of the embryo in the mother’s womb.
• Where does fertilization occur in the case of a human female and name the place where the fertilized egg gets implanted?

Answer:

1. Male — Testis. Hormone — Testosterone along with producing sperm.

Female — Ovary. Hormone — Oestrogen along with producing ova.

2. Embryo in Mother’s Womb: 

• Protection from the outside environment
• Provision for nourishment, exchange of gases, and removal of waste products.

3. Site of Fertilization:

Junction of ampulla and isthmus parts of the fallopian tube.

Implantation: The fertilized egg is implanted in the uterus.

Question 45.

1. Give an example of a bisexual flower. What is its female reproductive part known as?
2. Pollination may occur without fertilization but fertilization will not take place without pollination. Give reasons.

Answer:

1. Bisexual Flower: Mustard, Petunia, Female Reproductive Part. Pisfil

2. Pollination is the first step while fertilization is the second step. Fertilization can occur only when pollination has occurred and the pollen tube has carried the male gametes into the embryo sac. However, if the latter does not occur, pollination may occur but will be of no consequence.

Question 46. Give reason for the statement — since the ovary releases one egg every month, the uterus also prepares itself every month by making its lining thick and spongy.
Answer:

An egg released once a month can get fertilized and transform itself into an embryo. The embryo requires fixation, nourishment, and oxygen which can be provided by the uterus. Therefore, the uterus prepares itself for that eventuality every month.

Question 47. In a germinating seed which parts are known as future shoot and future root? Mention the functions of cotyledons.
Answer:

Future Shoot:  Plumule.

Future Root: Radicle.

The function of Cotyledons:

1. Store and supply of food to embryo
2. Functioning as the first leaves of the seedling.

Question 48. What is the placenta? Write any two major functions of the placenta.
Answer:

The placenta is a disc-shaped spongy structure that attaches the fetus to the uterine wall through the umbilical cord.

Functions of Placenta:

1. Provides attachment to fetus.
2. It is the source of nourishment to the fetus.
3. The exchange of gases and removal of waste products of the fetus is also carried out by the placenta.

Question 49.  In a flowering plant, summarise the events that take place after fertilization.
Answer:

Fertilization produces two structures, a diploid zygote and a triploid primary endosperm cell. The zygote undergoes divisions and produces an embryo. Primary endosperm cell forms a nutritive tissue called endosperm. The endosperm may persist or get consumed. Ovule matures into a seed. It develops a thick seed coat. Ovary matures into fruit. Fruit encloses the seeds.

Question 50.

1. 

1. Where the block is created surgically to prevent fertilization
2. Where Cu-T is inserted
3. Inside which condom can be placed.

2. Why do more and more people prefer to use condoms? What is the principle behind the use of condoms?

Answer:

1. 

1. Block: Both the oviducts or fallopian tubes,
2. CuT: Inside the uterus
3. Condom:  Inside vagina.

2. More people prefer condoms as

• They do not have any side effect
• Condoms are disposable
• They protect against catching sexually transmitted diseases.

Question 51.

1. Describe the various steps involved in the process of binary fission with the help of a diagram.
2. Why do multicellular organisms use complex ways of reproduction?

Answer:

1. Binary fission is a mode of asexual reproduction in unicellular organisms in which a mature individual divides into two daughter cells, both of which behave as new individuals.

• For binary fission, there is an enlargement of the parent cell.
• Simultaneously nucleus (or nuclear matter) elongates.
• The nucleus constricts in the middle and divides into two.
• The cell also constricts between the two nuclei,
• There is a division of the parent cell into two daughter cells, each with a nucleus. The parent cell disappears.

2. Multicellular organisms cannot divide and multiply cell by cell. They have organization of specialized cells to form tissues and tissues to form organs. Some organs called reproductive organs become specialized to produce propagules or reproductive cells. Only they take part in reproduction. Therefore, multicellular organisms use complex way of reproduction.

Question 52.

1. Describe the role of the prostate gland, seminal vesicles, and testes in human male reproductive systems.
2. How is surgical removal of unwanted pregnancies misused?
3. Explain the role of oral contraceptive pills to prevent conception.

Answer:

1.

1. Prostate Gland: Forms 20-30% of semen plasma. Secretion is essential for the mobility of sperm and ejaculation of semen.
2. Seminal Vesicles: Forms 60-70% of semen plasma. The secretion contains nutrients, fibrinogen, and prostaglandins.
3. Testes:  Secrete testosterone hormone and produce sperm. The hormone brings about changes in the males during puberty and helps maintain male sex characters.

2. Surgical removal of unwanted pregnancies has been misused for female foeticide. Because of it, the sex ratio started declining. Therefore, prenatal sex determination has been banned. Abortions are undertaken only when it is essential in the opinion of doctors.

3. Oral contraceptives contain progesterone which inhibits ovulation. In the absence of ovulation, pregnancy cannot occur.

Question 53. Trace the changes that take place in a flower from gamete formation to fruit formation. 
Answer:

• The stamen is the male organ of a flower. In the region of its anther, four pollen sacs develop. They produce pollen grains.
• The pistil is the female organ of a flower. It has a receptive part called the stigma and an ovule-bearing part called the ovary. Each ovule contains a female gametophyte called embryo sac. An embryo sac has a female gamete or oosphere and a diploid central cell.
• In the process of pollination, pollen grains are transferred to the stigma of the pistil. A pollen grain germinates and develops a pollen tube. The pollen tube contains two male germ cells.
• Pollen tube passes through the style, reaches the ovary, and enters an ovule. In the embryo sac region, it bursts open to release the two male germ cells.
• One germ cell fuses with the female germ cell or oosphere to form a zygote. The zygote undergoes repeated divisions and forms an embryo.
• The second germ cell fuses with the central cell to produce the primary endosperm cell. The latter undergoes divisions and forms endosperm.
• The fusion of both the male gametes with two different structures in the same embryo sac is called double fertilization. The fusion of a second male germ cell with the central cell is called triple fusion.
• After fertilization, the ovules develop into seeds. The ovary grows around the seeds and produces fruit.

Question 54.

1. Differentiate between germination and fertilization.

2. Differentiate between pollen and ovule.

3. What happens to the following parts after fertilization :

1. Ovum
2. Ovary
3. Ovule 
4. Sepals and petals.

Answer:

1. Germination:

Germination is the growth of contents of a propagule or spore as a pollen tube from a pollen grain, seedling from seed, new mycelium from a sporangiospore.

Fertilization:

Fertilization is a fusion of two haploid gametes to form a diploid zygote.

2. Pollen Grain:

It is a haploid spore that is formed by the meiotic division of pollen grain mother cell inside a spore sac or microsporangium. Ovule is integument megasporangium. It develops a single haploid megaspore which grows to form embryo sac or female gametophyte. While pollen grain degenerates after fertilization, the ovule develops into seed after fertilization.

3. After Fertilization:

1.  Ovum forms a diploid zygote. The embryo develops from the same.
2. Ovary matures into fruit,
3. Ovule develops into a seed,
4. Sepals and Petals.

They shrivel and fall. Sepals persist in the fruits of some plants.

Question 55. Rajesh observed a patch of greenish-black powdery mass on a state piece of bread.

1. Name the organism responsible for this and its specific mode of asexual reproduction.
2. Name its vegetative and reproductive parts.

Answer:

1. The greenish-black powdery mass found on a piece of bread is due to the growth of bread mold Rhizopus. Its specific mode of asexual reproduction is spore formation or sporulation.

2. Vegetative Parts:

Hyphae. They are thread-like structures lying over and inside the bread.

Reproductive Parts:  Blob-like blackish sporangia borne on aerial hyphae called sporangiophores.

Question 56. The diagram depicts pollination. Choose the options that will show a maximum variation in the offspring.

1. 1, 2 and 3
2. 2 and 4
3. 2, 3 and 4
4. 1 and 3

Answer:   4. 1 and 3, They involve cross-pollination

Question 57. 

1. Why is not possible to reconstruct the whole organisms from a fragment in complex multicellular organisms
2. Sexual maturation or reproductive tissue and organs are necessary links for reproduction. Elucidate

Answer:

1. A multicellular organism hi not a random collodion ofcclla. II lias well-differentiated eclhi which are organized into limits and tissues into organs, They occur at specific places in Ihc body. A fragment of a complex multicellular organism cannot have differentiated cells for cell-by-cell division. Further regeneration in complex oi gallium is under the control of nerves and hormones,

2. Reproductive tissues and organs become functional only on full sexual maturation. It takes a long time beginning at puberty and is completed at the end of adolescence, Puberty produces immature sex organs which begin to produce hormones Under The influence of hormones when general body growth begins to slow down reproductive tissues and organs begin to mature.

New sets of changes appear in the body like changes in body proportions, menstruation, increase in breast size, and darkening of The skin of the nipples al lips of breasts in girls. In boys (there is a thick growth of hair on the face. ‘Their voice also begins to crack,

Question 58. 

1. How are variations useful for species if there Is drastic alteration in the niches?
2. Explain how the uterus and placenta provide necessary conditions for proper growth and development of the embryo after Implantation.
   

Answer:

1. A drastic change in niches means that The population of niches will not only lose their habitat but also the emotional areas for obtaining their food. In such a situation the whole population of a niche could be wiped out.

However, this generally does not occur because of the presence of variations in some individuals which are useful in the new niche. These individuals with variations will not only survive but also take part in the multiplication and formation of the population again. Therefore, variations are useful for the survival of species over time.

2. The placenta is a disc-shaped structure formed by the joint activity of the uterus and embryo. It helps in the proper attachment of the fetus inside the uterus.

‘The wall of the uterus thickens and becomes highly vascularised. The embryo part of the placenta develops finger-like outgrowths or villi for proper fixation and absorption. They are surrounded by uterine blood spaces or sinuses. A large surface area develops for the exchange of materials between the mother and fetus. The mother provides glucose and oxygen to the embryo. Waste of embryo and carbon dioxide is picked up by the mother’s blood. As the fetus matures, the uterus undergoes rhythmic contractions to expel the child.

Question 59. From the internet, gather information about the chromosome number of five animals and five plants.
Correlate the number with the size of organisms and answer the following questions :

• Do larger organisms have more number of chromosomes/cells?
• Can organisms with fewer chromosomes reproduce more easily than organisms with more number of chromosomes?
• The more the number of chromosomes/cells greater is the DNA content. Justify.

Answer:

1. No. there is no relationship between the number of chromosomes and the size of the organism. However sized organisms have a larger number of cells as compared to smaller sized organisms.

2. No. The process of reproduction is independent of number of chromosomes.

3. Chromosomes are made of DNA (+ protein). More chromosomes and more number of cells means more

Question 60. Why are budding, fragmentation and regeneration all considered asexual types of reproduction? With neat diagram, explain the process of regeneration in Planaria.
Answer:

Budding, fragmentation and regeneration are asexual modes of reproduction because

1. They are uniparental
2. Only mitotic divisions are involved.
3. Formation and fusion of gametes do not occur.

Regeneration in Planaria:

Regeneration is the faculty to repair and replace injured and lost parts. If Planaria is cut into two or three pieces, each piece grows the lost parts and forms the complete animal. This is accomplished by two types of developments, activation of stem cells and dedifferentiation of differentiated cells. The cells grow, divide, undergo differentiation and produce the lost parts.

Question 61. Write two points of differences between asexual and sexual types of reproduction. Describe why variations
are observed in the offspring formed by sexual reproduction.
Answer:

Differences between asexual and sexual types of reproduction:

Question 62. Distinguish between a gamete and a zygote. Explain their role in sexual reproduction.
Answer:

Distinguish between a Gamete and a Zygote:

Role of Gamete:

It is a specialized structure that takes part in sexual reproduction. For this gamete has received half the number of chromosomes from its parent. The creation of the chromosomes is carried out by meiosis. Variations appear due to random separation of chromosomes and crossing over.

Role of Zygote:

It is slightly different genetically from the parents due to crossing over, random separation and random coming together of chromosomes. The zygote undergoes mitotic division to form an embryo. The embryo grows to form an adult organism.

Question 63. Reproduction is essentially a phenomenon that is not for the survival of an individual but for the stability of a species. Justify? can
Answer:

Survival and reproduction are two different phenomena. Survival or living depends upon the input of energy and the elimination of wastes. Reproduction is the formation of young ones by the grown-up individuals. While survival is connected with the living of the individual, reproduction is connected with the continuation of the species even after the death of individuals as it has added new individuals.

• Continuity of Life:  Reproduction has helped in the continuation of life on Earth since its origin.
• Perpetuation of Species: It allows indefinite perpetuation of a species.
• Organization:  It maintains the organization or composition of different ages of individuals—young, adults, and old.
• Variations:  Reproduction adds some variations that help the species to adapt to a changing environment.
• Transfer of Variations: Useful variations are transferred to the progeny through reproduction.

Question 64. Describe the sexually transmitted diseases and mention the ways to prevent them.
Answer:

• Sexually Transmitted Diseases:  (STDs) are those infectious diseases that get transmitted from an infected person to a healthy person during sexual contact They are also called venereal diseases (VD).
• Gonorrhea:  It is a bacterial disease spread by Neisseria gonorrhea. Gonorrhoea spreads through sexual contact, and common toilets and produces pus-containing discharge. There is a burning sensation during urination. Pain occurs around the genitalia.
• Syphilis:  It is a bacterial disease spread by Treponema pallidum. Painless ulcers develop on the genitalia. Lymph glands swell up. Skin lesions, rashes, and hair loss occur later on.
• Genital Warts:  The disease is spread by Human Papilloma Virus through sexual contact. Warts occur over the genitalia and peri-anal area. Warts may enter the vagina and cause pain in women.

AIDS (Acquired Immune Deficiency Syndrome):

The disease is produced by HIV (Human Immunodeficiency Virus) through sexual contact, used syringes, common needles, and other means of blood contact. T-helper cells decrease in number. Immunity is reduced and many minor infections become extremely harmful.

Prevention:  1. Say no to multi-partner sex. 2. Use condoms during sex

Question 65. How does fertilization take place? Fertilization occurs once in a month. Comment.
Answer:

• Fertilization occurs in the ampulla-isthmus junction of the oviduct. The egg released by the ovary rests there for a few hours.
• If the sperms are available in the female genital tract, they reach the region of stay of ovum.
• One sperm breaks the covering of the ovum and passes its head and middle part into it.
• This causes fertilization. Fertilization occurs only once a month as only one ovum is released once in a month from one of the two ovaries.
• It occurs roughly in the middle of the menstrual cycle.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Short Question And Answers

Question 1. In the Tobacco plant, the male gametes have twenty-four chromosomes.

1. What Is the number of chromosomes in the female gamete?
2. What is the number of chromosomes in the zygote?

Answer:

1. 24 chromosomes.
2. 48 chromosomes (24 + 24)

Question 2. A flower and label the four whorls. Write the name of gamete-producing organs in the flower.
Answer:

L abel the four whorls of the

1. Calyx
2. Corolla
3. Androecium and
4. Gynoecium.

Male Gametes Producing Part: Another part of the stamen that forms pollen grains.

Female Gametes Producing Part:  Ovule (Embryo sac) contained in ovary part of pistil.

Question 3. What is the placenta? Mention its role during pregnancy.
Answer:

The placenta is a discoid spongy connection present in the pregnant female between the uterine wall and the foetus. It has many villi and blood sinuses to increase the surface area of the connection between the two.

Role During Pregnancy

• Attachment of fetus to the uterus.
• Providing nutrients to the fetus.
• Supply of oxygen to fetus and removal of carbon dioxide.
• Removal of wastes from the fetus.

Question 4.

1. Trace the path a male gamete takes to fertilize a female gamete after being released from the penis.
2. State the number of sets of chromosomes present in a zygote.

Answer:

1. The male gamete is released in the vagina. From here it travels to the rest of the female tract of the uterus and then the fallopian tube. It fuses with the ovum if present in the junctional area of the ampulla and isthmus. The fusion produces a zygote.
2. The zygote comes to have two sets of chromosomes, one set each of male and female gametes.

Question 5. What is the role of seminal vesicles and the prostate gland?
Answer:

Seminal Vesicles:

Their secretions constitute 60-70% of semen plasma. It is alkaline and viscous. It contains fructose, proteins, fibrinogen, and prostaglandins. Prostaglandins cause movement in the genital tract of the female which helps in the quicker passage of sperm. Alkaline salts help neutralize the acidity of the female tract. Sperms are nourished and activated by secretions of seminal vesicles.

Prostate Gland:

Its secretion forms 20-30% of semen plasma. The secretion is milky, viscous, and alkaline. It is essential for the motility of sperm and ejaculation of semen.

Question 6. How does the embryo get nourishment inside the mother’s body?
Answer:

The embryo gets nourishment from the mother’s body through the placenta. The placenta is a disc-shaped structure embedded in the endometrium of the uterus. It has finger-like villi from the embryo which are surrounded by blood sinuses of the endometrium. there is a large surface area for the diffusion of material from the mother’s blood into the villi of the embryo. Glucose, amino acids vitamins, and other biochemicals pass from the mother’s blood into an embryo.

Question 7. If a woman is using copper – T, will it help in preventing sexually transmitted diseases
Answer:

No. copper – T occurs in the uterus. Sexually transmitted diseases are acquired through fluid contact that occurs in the vagina between male and female

Fertilization is the process of

1. Transfer of male gamete to female gamete
2. Fusion of nuclei of male and female gametes
3. Adhesion of male and female reproductive organs
4. The formation of gametes by a reproductive organ.

Answer: 2. Fusion of nuclei of male and female gametes

Question 8. Name one sexually transmitted disease each caused by a bacterial infection and viral infection. How can they be prevented?
Answer:

Bacterial STD: Gonorrhea/Syphilis.

Viral STD: Warts/HJV-AIDS

1. Prevention:
2. Use of condom
3. Clean toilets
4. Use of disinfectants
5. Avoiding multi-partner sex.

Question 9. List two functions performed by testes in human beings.
Answer:

1. Sperms: Formation of sperms from cells of seminiferous tubules.
2. Testosterone: It is a male sex hormone that is produced by Leydig cells present in the connective tissue of the testes.

Question 10. Name the male and female gametes in animals. What is fertilization and where does it take place in human females?
Answer:

1. Male Gamete – Sperm or spermatozoan.
2. Female Gamete – Ovum or egg.
3. Fertilization –  It is the fusion of haploid sperm (male gamete) and egg or ovum (female gamete) to form a diploid zygote.
4. Site of Fertilization- Ampulla-isthmus junction of the oviduct.

Question 11. State in brief two functions of copper-T used by some women.
Answer:

• Immobilization of sperms
• Prevention of implantation.

Question 12. In what respect is the human male gamete different from the female gamete? What is the importance of this difference?
Answer:

Male gamete is smaller vibratile and dart-like with reserve food only for its locomotion in the female genital tract. Many of the cytoplasmic organelles are absent. On the other hand, the female gamete or ovum is larger, rounded, non-motile, and full of cytoplasmic contents as well as reserve food for the early growth of the zygote if fertilization takes place.

Question 13. What are sexually transmitted diseases? Name one STD which damages the immune system of the human body.
Answer:

Sexually transmitted diseases (STDs) are those infectious diseases that get transmitted from an infected person to a healthy person during sexual contact. They are also called venereal diseases. The sexually transmitted disease that damages the immune system of the body is AIDS caused by HIV.

Question 14. State the significance of human testes being located in the scrotum.
Answer:

Significance : 

• The scrotum provides proper space for the testes,
• It functions as a thermoregulator keeping the temperature at about 34-35°C, 1-3°C below that of the body (37°C). (in) In excessive cold, the scrotum contracts to bring testes near the body while in hot season it becomes extra loose to lower the temperature. A lower temperature is required for sperm formation.

Question 15. 

1. What will happen to the ovary and ovule after fertilization in the angiospermic plant?
2. What are the male and female gonads in human beings known as ?

Answer:

1. After fertilization, the ovary gets transformed into the fruit while the ovule forms the seed.

2.

1. Male Gonads. Testes.
2. Female Gonads. Ovaries.

Question 16.  Name the sex hormones secreted by male and female sex organs in human beings. State one function of each.
Answer:

Sex Hormone in Male Human. Testosterone.

It is essential for sperm formation and maintenance of male characteristics:

Hormones by female humans

1. Estrogen:  Ovulation and maintenance of female characteristics
2. Progesterone:  Development of endometrium.

Question 17. Prenatal sex determination has been prohibited by law. State two reasons.
Answer:

1. The desire for a male child has prompted many parents to know the sex of the fetus.
2. It has resulted in large-scale female foeticide,
3. The sex ratio started declining drastically. Therefore, prenatal sex determination has been banned by law. Under the law, offenders are severely punished.

Question 18.

1. Name two bacterial STD infections.
2. How do oral pills prevent pregnancy?

Answer:

1. Bacterial STD Infections. Gonorrhoea, Syphilis.

2. Oral pills contain progesterone which inhibits ovulation. In the absence of ovulation, there cannot be any pregnancy.

Question 19.

1. Differentiate between unisexual and bisexual flowers. 
2. Which of the following plants produce unisexual flowers: Watermelon, Hibiscus, Mustard, Papaya.

Answer:

1.  A unisexual flower bears only one type of essential organ, either stamens or pistils but not both. A bisexual flower is one that possesses both the essential organs of stamens and pistils. (ft)

2. Watermelon, Papaya.

Question 20.

1. Which organ is responsible for the implantation of a zygote?
2.  State the function of fallopian tubes.

Answer:

1. Uterus, The Zygote gets transformed into a blastocyst which develops finger-like outgrowth or villi for implantation into the endometrium of the uterus.
2. The fallopian tube is the site of fertilization picks up the released ovum and conducts it to the uterus.

Question 21.

1. Name the structures in the human male reproductive system that deliver the sperms from the testes to the urethra.
2. Name the structure in the human female reproductive system that delivers the egg from the ovary to the uterus.

Answer:

1. Vasa efferentia, epididymis, vas deferens, ejaculatory duct.
2. Oviduct.

Question 22.

1. Write the advantages of sexual reproduction over asexual reproduction.
2. Name the male and female parts of a flower.

Answer:

1. Sexual reproduction introduces a lot of variations which asexual reproduction does not. It maintains the adaptability, competitiveness, vigor and vitality of the individuals.

2.

1. Male – Stamens.
2. Female-  Carpels (= pistils).

Question 23. What is pollination? How does it take place?
Answer:

Pollination is the passage of pollen grains from the anther to the stigma. It is of two types, self and cross¬ pollination. In self-pollination, the pollen grains from the anther are shed over the stigma of the same flower. In cross-pollination, the pollen grains from the anther of one flower reach the stigma of the plant flower with the help of an abiotic

Example:  Air, Water, or biotic agency (insects, birds, bats, etc).

Question 24. Which parts/organs of the human reproductive system perform the following functions : 

1. Site of implantation of the zygote. 
2. Entry of sperm in the female reproductive system.

Answer:

1. Site of Implantation – Uterus.
2. Entry of Sperms – Vagina.

Question 25. Give two differences between radicle and plumule.
Answer:

1. The radicle is the positively geotropic part of the embryo while the plumule is the negatively geotropic part,
2. Radicle is the future root while plumule is the future shoot.
3. The tip of the radicle does not bear leaf primordia which are present over the plumule tip.

Question 26. List two suitable differences between pollen grain and ovule.
Answer:

• Pollen grain represents spore while ovule represents sporangium.
• Pollen grain develops into a male gametophyte with two male gametes while ovule develops a female gametophyte or embryo sac with a single female gamete.

Question 27. The chromosome number of sexually reproducing parents and their offspring is the same. Justify the statement.
Answer:

Chromosome number remains the same generation after generation in sexually reproducing organisms due to the occurrence of the meiotic cycle during sexual reproduction.

The gametes are always haploid as they are formed after meiosis in their parent cells. The haploid gametes of two types fuse during fertilization. The fusion product or zygote is diploid. The offspring formed from it will be diploid just as the nature of parents.

Question 28. What are sexually transmitted diseases? Name four such diseases. Which one of them damages the immune system of the body?
Answer:

Sexually Transmitted Diseases or STDs are those infectious diseases that are transmitted from an infected person to a healthy person through sexual contact.

Examples:  Gonorrhoea, Syphilis (bacterial infection), Warts, HIV-AIDS (viral infection).

The immune system of the body is damaged by viral infection of AIDS (acquired immunodeficiency syndrome) because the virus (HIV) multiplies in macrophages and helper T-4 lymphocytes.

Question 29.

1. Why is the male reproductive system called the urinogenital system?
2. Give a reason to explain why cross-pollination is preferred over self-pollination.

Answer:

1. The male reproductive system is called the urinogenital system because its passageway of sperm is the passage of urine from the body.
2. Cross-pollination is preferred over self-pollination as it produces several variations, suppresses harmful traits, and maintains the vigor and vitality of the plants.

Question 30.

1. How do oral pills function as contraceptives?
2. The use of these pills may be harmful. Why?

Answer:

1. Oral pills contain progesterone which prevents ovulation. Contraception occurs due to the non-formation of eggs.
2. Oral pills disturb the secretory activity of the pituitary. This may result in hormonal imbalance. Side effects are due to that.

Question 31. Name the reproductive parts of an angiosperm. Where are these parts located? Explain the structure of its male reproductive part.
Answer:

Two male stamen, a female pistil (carpel). Both of them occur in flowers.

Male Reproductive Part or Stamen:

It has two parts, a stalk-like filament and a terminal knob-like anther. Anther has four pollen sacs where pollen grains are formed. Pollen grains give rise to male gametes.

Question 32. What is puberty? Mention any two changes that are common to both boys and girls in their early teenage years.
Answer:

Puberty is the early phase of development of sex organs in young persons which secrete hormones for further development to adulthood.

Changes:

1. Growth of hair in armpits and grains.
2. Skin becomes oily and may develop pimples, especially over the face.

Question 33. What is reproduction? List its two types. How are the modes of reproduction different in unicellular and multicellular organisms?
Answer:

Reproduction:

Reproduction is the process of formation of new young individuals of similar type by the adult individuals of a species. It is of two types, sexual and asexual. For differences in the modes of reproduction in unicellular and multicellular organisms.

Question 34. In the female reproductive system of human beings, the functions of

1. Ovary 
2. Oviduct.

Answer:

• The function of the Ovary: Formation of ova, secretion of hormones, estrogen, and progesterone.
• The function of the Oviduct:  Passage of ovum and site of fertilization of the ovum.

Question 35. 

1. State the significance of the pollen tube.
2. Name the parts of the flower that develop after fertilization into
   1. Seed
   2. Fruit

Answer:

1. Significance of Pollen Tube: 

Carrying the male germ cell into the ovary and then the ovule to fuse with the female germ cell.

2.

1. Seed:  Formed from ovule
2. Fruit:  Formed from ovary.

Question 36. List two reasons for using contraceptives by married couples.
Answer:

1. Providing a gap between children
2. Prevention of unwanted pregnancies
3. Protection from STDs.

Question 37. Why does menstruation occur?
Answer:

Menstruation is the passing of broken endometrium, blood, and mucus from the vagina of the female in her reproductive period if an egg fails to get fertilized. It lasts for 2-5 days.

The cause of menstruation is the stoppage of nourishment of overgrown endometrium when hormonal support of progesterone and estrogen stops. The blood vessels of overgrown endometrium constrict. Non-supply of nourishment causes sloughing off the endometrium. It occurs due to the failure of the egg to get fertilized.

Question 38. What is a clone? Why do offspring formed by asexual reproduction exhibit remarkable similarity?
Answer:

• A clone is an individual that is an exact genetic copy of another individual.
• All the offspring formed asexually are clone of each other as well as their parent.
• They have remarkable similarities because they possess exact copies of DN/ of their parent.

Question 39. Explain how offspring and parents of organisms reproducing sexually have the same number of chromosomes.
Answer:

1. Both parents and offspring have a diploid (2N) number of chromosomes.
2. However, during gamete formation (both male and female), meiosis occurs which reduces the chromosome number to a haploid (IN) state.
3. As the two types of gametes fuse during fertilization, the diploid number of chromosomes (IN + IN) is restored.

Question 40. Colonies of Yeast fail to multiply in water but multiply in sugar solution. Give one reason for this.
Answer:

• Yeast obtains ready-made food from outside.
• Sugar solution provides it with the necessary food so that its colonies can multiply in it.
• They cannot do so in plain water as it is unable to supply the requisite food/energy.

Question 41. Why does bread mold grow profusely on a moist slice of bread rather than on a dry slice of bread ?
Answer:

• Both water and nutrients are required for the growth of bread Mould.
• Dry bread can provide nutrients but not water. In the absence of water, hyphae of bread Mould do not grow.
• However, moist bread supplies both water and nutrients.
• Therefore, Bread Mould grows profusely over it.

Question 42. Give two reasons for the appearance of variations among progeny formed by sexual reproduction.
Answer:

• Sexual reproduction produces variations in the progeny due to
• The Separation and coming together of chromosomes of two parents during the formation and fusion of gametes,
• The Crossing over of chromosome segments during meiosis or gamete formation.

Question 43. Is the chromosome number of zygote, embryonal cells, and adults of particular organisms always constant? How is the constancy maintained in these three stages?
Answer:

• All three stages have diploid chromosomes. The first diploid cell is zygote. It undergoes mitotic divisions to form embryonal cells.
• The latter also divide by mitosis to produce the adult organism. Mitosis maintains the chromosome number constant in the cells.
• Because of it, mitosis is called equational divisions.

Question 44. How are general growth and sexual maturation different from each other?
Answer:

• General growth is the sum of different development processes like increase in size, height, change in shape, and weight.
• Sexual maturation is the maturation of reproductive organs that are involved in sexual reproduction.
• It is indicated by puberty changes in boys and girls like new hair patterns, development of breasts in girls, and cracking voice in boys.

Question 45. Trace the path of sperm during ejaculation and mention the glands and their functions associated with the male reproductive system.
Answer:

• Sperms formed in the testis, first come into the vas efferent, vas deferens, and ejaculatory duct and from there into the urinogenital duct (urethra).
• On the way, sperms receive secretions from seminal vesicles and the prostate gland.
• Bulbourethral glands produce secretion for lubricating the urinogenital duct.
• Secretion of seminal vesicles provides liquid medium and nutrients.
• Secretion of the prostate gland activates the sperm.

Question 46. What changes are observed in the uterus after the implantation of the young embryo?
Answer:

• The inner layer of the uterus or endometrium thickens and becomes more spongy, glandular and vascular.
• A special disc-shaped tissue called the placenta develops in the region of contact between the embryo and the uterus.
• It not only attaches the embryo but also functions as a junction for the exchange of materials between the embryo and the mother (providing nutrients and oxygen and taking away carbon dioxide and wastes).

Question 47. What are the benefits of using mechanical barriers during sexuality?
Answer:

This is a double benefit of using mechanical barriers like condoms.

• The sperms are not liberated in the genital tract of the female so that no pregnancy will occur.
• There is no tissue-to-tissue contact between the two partners so that the infection of one is not transferred to the other

Question 48. Name the part of the female reproductive system that takes part in 

1. Production of egg.
2. Site of fertilization 
3. Site of implantation
4. Entry of sperms

Answer:

1. Production of egg  ……Ovary.
2. Site of fertilization ……Oviduct (ampulla- isthmus junction)
3. Site of Implantation ……..Uterus.
4. Entry of sperms. ……….. Vagina.

Question 49. What would be the ratio of chromosome number between the egg and its zygote? How is the sperm genetically different from the egg?
Answer:

• The egg is haploid (N) while the zygote is diploid (2N). Therefore, the ratio of their chromosome number is 1: 2.
• All eggs have one type of genetic constitution (22 + X). Sperms are of two types (22 + X and 22 + Y).

Question 50.

1. Distinguish between pollination and fertilization. Mention the site and product of fertilization in a flower.
2. Draw a neat diagram of a pistil showing pollen tube growth and its entry into ovule

Answer:

1. Pollination is the transfer of pollen grains from another to the stigma ofa flower. Fertilization is the fusion of two types of gametes.
2. The site of fertilization is the ovule (embryo sac). The product of fertilization in a flower is a diploid zygote and triploid primary endosperm cell

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Multiple Choice Questions

Question 1. In the list of organisms given below, those that reproduce by asexual method are :

1. Banana
2. Dog
3.  Yeast
4. Ameoba

1. 1 and 2

2. 1, 3 and 4

3. 1 and 4

4. 2,3, and 4

Answer: 2. 1, 3 and 4

Question 2. In a flower, the parts that produce male and female gametes (germ cells) are :

1. Stamen and anther
2. Filament and stigma
3. Anther and ovary
4. Stamen and style.

Answer: 3. Anther and ovary

Question 3. Which of the following is the correct sequence of events of sexual reproduction in a flower?

1. Pollination, Fertilization, seedling, embryo
2. Seedling, embryo, fertilization, pollination
3. Pollination, fertilization, embryo, seedling
4. Embryo, seedling, pollination, fertilization

Answer: 3. Pollination, fertilization, embryo, seedling

Question 4. Offspring formed by the asexual method of reproduction have greater similarity among themselves because 

1. Asexual reproduction involves only one parent
2. Asexual reproduction does not involve gametes
3. Asexual reproduction occurs before sexual reproduction
4. Asexual reproduction occurs after sexual reproduction.

1. 1 and 2

2. 1 and 3

3. 2 and 4.

4. 3 and 4

Answer: 1. 1 and 2

Question 5. Characters transmitted from parents to offspring are present in

1. Cytoplasm
2. Ribosome
3. Golgi bodies
4. Genes

Answer: 4.  Genes.

Question 6. Characters that are transmitted from parents to offspring during reproduction show 

1. The only similarities between parents
2. Only variations with parents
3. They are all unicellular
4. Both similarities and variations with parents
5. Neither similarities nor variations.

Answer: 3. They are all unicellular

Question 7. A feature of reproduction that is common to Amoeba, Spirogyra and Yeast is that :

1. They reproduce asexually
2. They are all unicellular
3. They reproduce only sexually
4. They are all multicellular

Answer: 1. They reproduce asexually

Question 8. In Spirogyra, asexual reproduction takes place by :

1. Breaking up of filaments into smaller bits
2. Division of a cell into two cells
3. Division of a cell into many cells
4. Formation of young cells from older cells.

Answer: 1. Breaking up of filaments into smaller bits

Question 9. The ability of cell to divide into several cells during reproduction in Plasmodium is called.

1. Budding
2. Reduction division
3. Binary fission
4. Multiple fission

Answer: 4. Multiple fission.

Question 10. The correct sequence of reproductive stages seen in flowering plants is 

1. Gametes, zygote, embryo, seedling.
2. Zygote, gametes, embryo, embryo,
3. Seedling, embryo, zygote, gametes
4. Gametes, embryos, zygotes, seedlings.

Answer: 1. Gametes, zygote, embryo, seedling

Question 11. The number of chromosomes in parents and offspring of a particular species remains constant due to :

1. Doubling of chromosomes after zygote formation
2. Halving of chromosomes during gamete formation
3. Doubling of chromosomes after gamete formation
4. Halving of chromosomes after gamete formation.

Answer: 2. Halving of chromosomes during gamete formation

Question 12. In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called :

1. Filaments
2. Hyphae
3. Rhizoids
4. Roots.

Answer: 2. Hyphae

Question 13. Vegetative propagation refers to the formation of new plants from :

1. Stem, roots, and flowers
2. Stem, roots, and leaves
3. Stem, flowers, and fruits
4. Stem, leaves, and flowers.

Answer: 2. Stem, roots and leaves

Question 14. Factors responsible for the rapid spread of bread mold on slices of bread are :

1. A large number of spores
2. Availability of moisture and nutrients in bread
3. Presence of tubular branched hyphae
4. Formation of round-shaped sporangia.

1. 1 and 3

2. 1 and 2

3. 2 and 4

4. 3 and 4.

Answer: 3. 2 and 4

Question 15. The length of the pollen tube depends on the distance between

1. Pollen grain and upper surface stigma
2. Pollen grain on the upper surface of the stigma and ovule
3. Pollen grain in anther and the upper surface of stigma
4. The upper surface of the stigma and the lower part of the style.

Answer:  2. Pollen grain on the upper surface of stigma and ovule

Question 16. Which of the following statements are true for flowers?

1. Flowers are always bisexual
2. They are the sexual reproductive organs
3. They are produced in all groups of plants
4. After fertilization, they give rise to the fruits

1. 1 and 4

2. 2 and 3

3. 2 and 3

4. 1 and 4

Answer: 4. 1 and 4

Question 17. Which of the following statements are true for unisexual flowers?

1. They possess both stamen and pistil
2. They possess either stamen or pistil
3. They exhibit cross-pollination
4. Unisexual flowers possessing only stamens cannot produce fruits.

1. 1 and 4

2. 2, 3 and 4

3. 3 and 4

4. 1, 3, 4

Answer:  2. 2, 3 and 4

Question 18. Which of the following statements is true for sexual reproduction in flowering plants?

1. It requires two types of gametes
2. Fertilization is a compulsory event
3. It always results in the formation of a zygote
4. Offspring formed are clones.

1. 1 and 4

2. 1, 2 and 4

3. 1,2, and 3

4. 2, and 3

Answer: 3. 1,2, and 3

Question 19. In the figure the parts a, b, and c arc sequentially :

1. Cotyledon, plumule, and radicle
2. Plumule, radicle, and cotyledon
3. Plumule, cotyledon, and radicle
4. Radicle, cotyledon, and plumule

Answer: 3.  Plumule, cotyledon, and radicle

Question 20. Offspring formed as a result of sexual reproduction exhibit more variations because :

1. Sexual reproduction is a lengthy process
2. Genetic material comes from two parents of the same species
3. Genetic material comes from two parents of different species
4. Genetic material comes from many parents.

Answer: 2. Genetic material comes from two parents of the same species

Question 21. Reproduction is essential for living organisms to:

1. Keep the individual organisms alive
2. Fulfill their energy requirement
3. Maintain growth
4. Continue the species generation after generation.

Answer: 4. Continue the species generation after generation.

Question 22. During adolescence, several changes occur in the human body. Mark one change associated with sexual maturation in body :

1. Loss of milk teeth
2. Increase in height
3. Cracking of voice
4. Weight gain.

Answer: 3. Cracking of voice

Question 23. In human females, an event that reflects the onset of the reproductive phase is :

1. Growth of body
2. Changes in hair pattern
3. Change in voice
4. Menstruation.

Answer: 4. Menstruation.

Question 24. In human males, the testes lie in the scrotum, because it helps in the 

1. Process of mating
2. Formation of sperm
3. Easy transfer of gametes
4. All the above

Answer: 2. Formation of sperm

Question 25. Which among the following is not the function of testes at puberty :

1. Formation of germ cells
2. Secretion of testosterone
3. Development of placenta
4. Secretion of estrogen

1. 1 and 2

2. 2 and 3

3. 3 and 4

4. 1 and 4

Answer: 3. 3 and 4

Question 26. The correct sequence of organs in the male reproductive system for transport of sperms is :

1. Testis → Ureter→ Urethra
2. Testis → Urethra → Ureter
3. Testis → Vas deferens → Ureter.
4. Testis →Vas deferens → Ureter

Answer: 1. Testis → Ureter→ Urethra

Question 27. Which among the following diseases is not sexually transmitted

1. Syphilis
2. Hepatitis
3. HIV-AIDS
4. Gonorrhoea.

Answer: 2. Hepatitis

Question 28. Which is not essential to maintain life?

1. Nutrition
2. Respiration
3. Excretion
4. Reproduction.

Answer: 4. Reproduction.

Question 29. A basic event in reproduction is 

1. Creation of DNA copy
2. Creation of an additional cellular apparatus
3. Creation of both DNA copy and additional cellular apparatus
4. Creation of variations.

Answer: 3. Creation of both DNA copy and additional cellular apparatus

Question 30. Under changed conditions, which one is helpful for species to survive :

1. Variations
2. Sexual reproduction
3. Asexual reproduction
4. All the above

Answer: 1. Variations

Question 31. A whip-like structure is present at the end of the cell in

1. Amoeba
2. Leishmania
3. Plasmodium
4. Yeast.

Answer: 2. Leishmania

Question 32. The plane of binary fission in Amoeba is :

1. Transverse
2. Vertical
3. Oblique
4. Any plane

Answer: 4. Any plane

Question 33. In multicellular organisms, reproduction is a function of :

1. Embryonic cells
2. Specific cell type
3. Specific areas consisting of several cell types
4. Stem cells.

Answer: 2. Specific cell type

Question 34. Regeneration is best known in

1. Planaria
2. Hydra
3. Both Planaria and Hydra
4. Hydra

Answer: 3. Both Planaria and Hydra

Question 35. Vegetative propagation is the only known method of reproduction :

1. Banana and Wheat
2. Banana and Jasmine
3. Jasmine and Maize
4. Orange and Pea.

Answer: 2. Banana and Jasmine

Question 36. After falling on the wet soil, the leaf of Bryophyllum :

1. Forms several plantlets
2. Forms a new plant
3. Forms several plantlets
4. Decays rapidly

Answer: 1. Forms several plantlets

Question 37. For vegetative propagation, a cut shoot of a money plant requires :

1. At least one internode
2. At least one node without a leaf
3. At least one node with a leaf
4. At least one root.

Answer: 3. At least one node with a leaf

Question 38. In Rliizopus culture, blebs represent :

1. Buds
2. Sporangia
3. Hyphae
4. Spores

Answer: 2. Sporangia

Question 39. Variations appearing in sexually reproducing organisms are :

1. Similar in progeny
2. Similar to a population
3. Similar in progeny
4. Mostly harmful.

Answer: 3. Similar in progeny

Question 40. The male gamete of complex organisms is 

1. Motile
2. Similar in progeny
3. Smaller in size
4. Similar in progeny

Answer: 4. Similar in progeny

Question 41. Reproductive parts of a flower are 

1. Sepals and petals
2. Similar in progeny
3. Stamens and carpels
4. Sepals and carpels.

Answer: 3. Stamens and carpels

Question 42. Pollen grains are

1. Yellowish
2. Pinkish
3. Greenish
4. Whitish.

Answer: 1. Yellowish

Question 43. Which part of the flower shrivels and falls off after fertilization?

1. Petals and sepals
2. Style and stigma
3. Style, stigma, and petals
4. Petals, sepals, stamens, style and stigma

Answer: 4. Petals, sepals, stamens, style, and stigma

Question 44. In humans, the development of sex organs is slow because of Their complicated nature

1. Occurrence of growth of body
2. Reduced intake of vitamins
3. Slow development of endocrine glands.
4. Devoid of stored food

Answer: 2. Reduced intake of vitamins

Question 45. The scrotum occurs in males 

1. In front of the penis
2. Inside the abdominal cavity.
3. Behind the penis
4. On the side of the penis

Answer:  1. In front of the penis

Question 46. Semen is formed from the secretion of :

1. Two seminal vesicles and two prostate glands
2. One seminal vesicle and one prostate gland
3. Two seminal vesicles and one prostate gland
4. One seminal vesicle and two prostate glands.

Answer: 3. Two seminal vesicles and one prostate gland

Question 47. Thousands of immature eggs grow in the ovaries of :

1. A newly born girl
2. A girl at puberty
3. A girl of five years
4. A woman near menopause.

Answer: 1. A newly born girl

Question 48. Placenta consists of

1. Villi from embryo
2. Sinuses from mother’s side
3. Both are embedded in the wall of the uterus
4. Umbilical cord

Answer: 3. Both are embedded in the wall of the uterus

Question 49. A nonfertilized human egg lives for:

1. Two days
2. One day
3. 3-5 days
4. 2-8 days

Answer: 2. One day

Question 50. Egg is not released in the contraceptive device of

1. Condom
2. Vasectomy
3. IUD
4. Oral pills

Answer: 4. Oral pills

Question 51. Which is not true about budding in Yeast?

1. It may arise from any part
2. A bud may form another bud
3. A bud separates and forms a new individual
4. A bud develops from a particular area of the parent cell.

Answer: 4. A bud develops from a particular area of the parent cell.

Question 52. A chain of yeast is formed due to 

1. Yeast cells do not separate after budding
2. Buds reproduce soon after formation
3. Daughter cells stick together by mucus
4. Daughter cells cannot survive without parent cells.

Answer: 2. Buds reproduce soon after formation

Question 53. A slide shows a cell and another smaller cell attached at the tip of the first cell. The slide is of

1. Yeast with a bud
2. Two daughter cells of Amoeba.
3. Two buds of yeast
4. Amoeba with bud

Answer: 2. Two daughter cells of Amoeba.

Question 54. In binary fission of Amoeba at the end of the process 

1. The identity of the parent cells is lost
2. A parent cell and a daughter cell are formed.
3. Division of cytoplasm begins
4. Two daughter nuclei are formed.

Answer: 1. Identity of the parent cells is lost

Question 55. What is true about Amoeba and Yeast?

1. Both reproduce by budding
2. Both reproduce by binary fission
3. Amoeba reproduces by budding and yeast by binary fission
4. Amoeba reproduces by binary fission and Yeast by budding.

Answer: 4. Amoeba reproduces by binary fission and Yeast by budding.

Question 56. In a slide of Amoeba which one shows binary fission :

1. Many pseudopodia and a small nucleus
2. Rounded body with round nucleus
3. Covered by the cyst and having many nuclei
4. Elongated nucleus and constriction in the middle of Amoeba.

Answer: 4. Elongated nucleus and constriction in the middle of Amoeba.

Question 57. To prepare the culture of Yeast, Yeast powder is added to :

1. Salt solution
2. Soap solution.
3. 0% sugar solution
4. Dilute hydrochloric acid

Answer: 1. Salt solution

Question 58. In binary fission, the total number of daughter cells formed is :

1. One
2. Many in chains
3. Two
4. Not definite.

Answer: 2. Many in chains

Question 59. Which is the correct sequence in the binary fission of Amoeba?

1. Formation of daughter cells
2. 3 Parent cell
3. Division of cytoplasm
4. 4 Division of nucleus.

1. 1,2,3,4

2. 4,3,2,1

3. 3,2,4,1

4. 3,4,2,1

Answer: 4. 3,4,2,1

Question 60. A yeast cell undergoing budding was found to have :

1. A chain of bud cells
2. Only one bud cell
3. Only three bud cells
4. Two bud cells.

Answer: 3. Only three bud cells

Question 61. In a slide, it was found that there is a cell and another similar cell of comparatively small size attached to the tip of the first cell. It is :

1. Amoeba with bud
2. Two daughter cells ofAmoeba
3. Two buds of Yeast
4. Yeast with bud.

Answer: 4.  Yeast with bud.

Question 62. Budding is a mode of

1. Sexual reproduction
2. Asexual reproduction
3. Gamete formation
4. Fertilization.

Answer: 2. Asexual reproduction

Question 63. Select correct statements regarding budding in Yeast 

1. A bud arises from a particular region on the parent body
2. A parent cell divides into two daughter cells where the identity of the parent is lost
3. Before detaching from the parent cell, a bud may form another bud
4. A detached bud grows into a new individual.

1. 1,2 and 3

2. 2,3 and 4

3. 3,4 and 1

4. 4,1 and 2

Answer:  3. 3,4 and 1

Question 64. The following steps describe binary fission in Amoeba :

1. The body of Amoeba elongates
2. Division of nucleus is followed by the division of cytoplasm
3. The nucleus elongates and becomes thinner at the center
4. Parent Amoeba divides into two daughter cells.

The correct sequence is :

1. 1,2, 3 and 4
2. 1,3, 2 and 4
3. 1,3, 4 and 2
4. 2,1, 3 and 4

Answer: 2. 1,3, 2 and 4

Question 65. Food required for the growth of the embryo of a pea seed is present in :

1. Radicle
2. Cotyledons
3. Plumule
4. Micropyle.

Answer: 3. Plumule

Question 66. Which part of the embryo comes out first during seed germination?

1. Radicle
2. Plumule
3. Hypocotyl
4. Epicotyl.

Answer: 1. Radicle

Question 67. Rearrange The steps to study parts of the embryo of the grant seed :

1. Soak Gram seeds in plain water and keep them overnight
2. Cut open the soaked seeds and observe the different parts
3. Take some dry Gram seeds in a petri dish
4. Drain excess water
5. Cover the soaked seeds with a wet cloth and leave them for the day.

1. 3,1, 5, 4 and 1

2. 3,1, 2, 4 and 5

3. 3,4, 5, 1 and 2

4. 3,1, 4, 5 and 2

Answer: 4. 3,1, 4, 5 and 2

Question 68. The small pore through which water enters a seed is called :

1. Plumule
2. Micropyle
3. Radicle
4. Cotyledon.

Answer: 2. Micropyle

Question 69. A dicotyledonous embryo consists of

1. Embryonal axis, two cotyledons
2. Epicotyl, hypocotyl, plumule
3. Cotyledons, plumule
4. Embryonal axis, hypocotyl.

Answer: 1. Embryonal axis, two cotyledons

Question 70. The region of epicotyl on the embryonal axis will form future 

1. Shoot
2. Root
3. Leaf
4. Embryo

Answer: 1. Shoot

Question 71. Which are correctly the parts of the embryo?

1. Tegmen
2. Testa
3. Cotyledon
4. Radicle
5. Plumule.

1. 1,2, 3,

2. 1,2, 3, and 4

3. 3,4, and 5

4. 1, 3, 4 and 5

Answer: 3. 3,4, and 5

Question 72. Which ones are dicot seeds?

1. Pea, Gram, Wheat
2. Red kidney Bean, Maize, Gram
3. Maize, Wheat, Red kidney bean
4. Red kidney bean, Pea, Gram

Answer: 4. Red kidney bean, Pea, Gram

Question 73. What does the figure depict?

1. Grafting
2. Stem cutting
3. Layering
4. Development of composite plants

Answer: 3. Layering

Question 74. The given figure represents

1. Binary fission in Amoeba
2. Cell division in Euglena
3. Binary fission in Paramecium
4. Binary fission in Leishmania

Answer: 1. Binary fission in Amoeba

Question 75. What does (1) represent in the diagram?

1. Nucleus
2. Acrosome
3. Head
4. Golgi complex

Answer: 2. Acrosome

Question 76. The figure is a diagrammatic exposition of

1. Breaking connection of ovaries from fallopian tubes
2. Cutting and tying of fallopian tubes
3. Blocking of cervix and uterus
4. Both 2 and 3

Answer: 4. Both 2 and 3

Question 77. Asexual Reproduction takes place through budding in 

1. Amoeba
2. Yeast
3. Plasmodium
4. Leishmania.

Answer: 2. Yeast.

Question 78. Which of the following is not a part of the female reproductive system in human beings?

1. Ovary
2. Uterus
3. Vas deferens
4. Fallopian tube.

Answer: 3. Vas deferens.

Question 79. The anther contains

1. Sepals
2. Ovules
3. Carpels
4. Pollen grains.

Answer:  4. Pollen grains.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Very Short Question And Answers

Question 1. In a bisexual flower, despite the young stamens being removed artificially, the flower produces fruit Provide a suitable explanation for the above situation.
Answer:

Bisexual flowers are generally cross-pollinated. Therefore, the removal of its stamens will not affect the pollination of its pistil and the formation of fruit

Question 2. Can you consider cell division as a type of reproduction in unicellular organisms? Give one reason.
Answer:

Yes. Cell division of unicellular organisms forms two daughter cells which behave as daughter individuals in reproduction.

Question 3. List three techniques that have been developed to prevent pregnancy. Which one of these techniques is not meant for males?
Answer:

Techniques: Barrier methods, hormonal and surgical. Hormonal methods are not meant for males.

Question 4. What is the significance of pollination?
Answer:

Significance: Pollination is essential for fertilization.

Question 5. Give an example of a unisexual flower.
Answer: Papaya, Cucurbita.

Question 6. Give an example of a flower which contains both stamens and carpels.
Answer: Mustard, Petunia. Such a flower is called a bisexual flower.

Question 7.  What are chromosomes?
Answer:  Chromosomes are thread-like strands of condensed chromatin (present in the nucleus) that contain genetic material or DNA.

Question 8. Would Planaria cut vertically develop into two individuals?
Answer: Yes. Planaria has a great regeneration ability. Both the cut parts regenerate the missing halves and form two complete animals.

Question 9. Why cannot fertilization take place in flowers if pollination does not occur?
Answer: Fertilization requires the fusion of male and female gametes. Pollination brings the male gamete. In the absence of a male gamete, fertilization cannot occur.

Question 10. Where is the zygote located in the flower after fertilization?
Answer:  A zygote or fertilized oosphere is formed inside the ovule which is present inside the ovary.

Question 11. What changes are observed in the uterus if fertilization does not occur?
Answer: Glands present in the uterine wall shrink. The spongy endometrium breaks slowly and comes out through the vagina as blood and mucus (menstruation). It lasts for 3-5 days.

Question 12. Reproduction is linked to the stability of the population of a species. Justify the statement.
Answer:

The stability of a species is based on the genetic similarity or constancy of chromosome number in all its members, present as well as future ones. Only minor variations occur due to the reshuffling of chromosomes, crossing over, and DNA replication.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Assertion And Reason Type Questions

In each question, two statements are given- one labeled Assertion and the other labeled Reason.

1. Both assertion and reason are true and reason is a correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. The assertion is false but the reason is true.

Question 1.

Assertion: Condom is the most common and useful contraceptive.

Reason: It protects the user from sexually transmitted diseases.

Answer: 1. Both assertion and reason are true and the reason is the correct explanation of the assertion.

Question 2.

Assertion: Oral pills are used by women as contraceptives.

Reason: They check the release of ova.

Answer: 1. Both assertion and reason are true and the reason is the correct explanation of the assertion.

Question 3.

Assertion:  Variations are essential for the survival of species over time.

Reason:  Many variations kill the new bom due to the incompatibility of changed DNA.

Answer: 2. Both assertion and reason are true but reason is not the correct explanation of the assertion.

Question  4.

Assertion: Multicellular organisms cannot divide cell by cell.

Reason: They have many simple ways of reproduction.

Answer: 3. Assertion is true but reason is false.

Question 5.

Assertion:  In Rhizopus, the spores have thin walls

Reason: A suitable medium helps in the quick germination of spores.

Answer: 4. Assertion is false but reason is true.

Question 6.

Assertion: Male gamete has little stored food. It is motile.

Reason:  Female gamete has stored food. It is non-motile.

Answer: 2. Both assertion and reason are true but reason is not the correct explanation of the assertion.

Question 7.

.Assertion: Carpel is present in the center of the flower.

Reason:  It gets pollinated by direct contact with the stamens.

Answer: 3. Assertion is true but reason is false.

Question 8.

Assertion: After fertilization, the zygote forms the embryo and the ovule develops a tough coat.

Reason:  Seed is to pass through unfavorable periods.

Answer: 1. Both assertion and reason are true and the reason is the correct explanation of the assertion.

Question 9.

Assertion:  A mother must be physically and mentally mature.

Reason:  She has to carry the fetus in the body for a long time.

Answer: 1. Both assertion and reason are true and the reason is the correct explanation of the assertion.

Question 10.

Assertion: The Scrotum provides a high temperature for the sperms to mature.

Reason:  The rate of sperm formation is maximum at about 34°C temperature.

Answer: 4. Assertion is false but reason is true.

Question 11.

Assertion: After fertilization, the ovum gets implanted.

Reason: The oviduct has a spongy lining to nourish the embryo.

Answer: 3. Assertion is true but reason is false.

Question 12.

Assertion: If the egg is not fertilized, it lives for about one day.

Reason:  Soon the lining of the uterine wall shrivels and breaks to produce menstruation flow.

Answer:  1. Both assertion and reason are true and the reason is the correct explanation of the assertion.

Question  13.

Assertion: Formation of warts is a venereal disease.

Reason: Surgical methods do not protect from venereal diseases.

Answer: 2. Both assertion and reason are true but reason is not the correct explanation of the assertion.

Class 10 Biology How Do Organisms Produce Chapter 3.3 Sexual Reproduction Paragraph Question And Answers

Question 1.  Read the following paragraph and answer  1 to 4

Rohit a brilliant and jovial student of class was looking sad and tried to remain solitary. On repeated inquiry from his best friend Parmesh, he told of his problem. He was suffering from pain during urination and had pus-containing discharge and irritation around his genitalia. Parmesh took Rohit to a doctor who asked several questions to Rohit, about girlfriends, family members, toilets, and recent visits to relatives and family friends. He then gave medicine to Rohit. Within a few days, Rohit became healthy.

1. What is the disease Rohit was suffering from?
Answer: Gonorrhoea

2. Why did the doctor ask Rohit about girlfriends?
Answer: Gonorrhoea is a sexually transmitted disease

3. What is the connection between Rohits visit to a relative and his disease?
Answer: Use of contaminated toilet can transmit the disease

4. What type of medicine did the doctor prescribe for Rohit?
Answer: Antibiotic

Question 2. Read the following paragraph and answer questions to 1 to 4

Micropropagation is the technique of multiplying plants from small pieces or explants over an artificial medium inside small containers under controlled environmental conditions. Each explant first forms a mass of undifferentiated cells called a callus. Callus can be subcultured several times. A callus formed from the meristematic region is always free from viral infection. Callus is provided with auxin and cytokinin. The treatment converts the undifferentiated mass of cells into small plantlets. The plant is transferred to a bigger container for hardening and acclimatization for later growing in the field.

1. What is the other name of micropropagation?
Answer: Tissue culture

2. Why is explant grown on artificial medium?
Answer: The artificial medium contains all nutrients required for the growth of cells

3. What is a callus?
Answer: The artificial medium contains all nutrients required for the growth of cells

4. Why are auxin and cytokinin provided to callus?
Answer: Auxin and cytokinin help in the growth and differentiation of cells to form parts of the plant.

Question 3. The pollen needs to be transferred from the stamen to the stigma. If this transfer of pollen occurs in the same flower, it is referred to as self-pollination. On the other hand, if the pollen is transferred from one flower to another, it is known as cross-pollination. This transfer of pollen from one flower to another is achieved by agents like wind, water, or animals. After the pollen lands on a suitable stigma, it has to reach the female germ cells which are in the ovary. For this, a tube grows out of the pollen grain and travels through the style to reach the ovary.

After reading the above, answer the questions to with the correct options :

1. Pollination is

1. Formation of pollen grains
2. Dispersal of pollen grains
3. Transfer of pollen to the stigma of a flower
4. Fusion of male gamete with female gamete.

Answer: 3. Transfer of pollen to the stigma of a flower

2. Transfer of pollen from the anther to the stigma of the same flower is

1. Self-pollination
2. Geitonogamy
3. Xenogamy
4. Allogamy

Answer: 1. Self-pollination

3. Why is an agency required for pollination?

1. Pollen grains are sticky
2. Pollen grains are non-motile
3. Pollen grains are heavy
4. Pollen grains are non-motile

Answer: 2. Pollen grains are non-motile

4. An agent of pollination is

1. Water
2. Air
3. Animals
4. All the above

Answer: 4. All the above

5. How is pollen grain able to send its contents in the area of female germ cells?

1. Germinating over stigma to release its contents
2. The arrival of the female germ cells over the stigma
3. Formation of a pollen tube that carries its contents to the area of the female germ cell
4. Eating its way through the style, reaches the ovary and passes to an ovule.

Answer: 3. Formation of a pollen tube that carries its contents to the area of the female germ cell

Question 4. Many ways have been devised to avoid pregnancy. These contraceptive methods fall in several categories. One category is the creation of a mechanical barrier so that sperm does not reach the egg. Condoms on the penis or similar coverings worn in the vagina can serve this purpose. Another category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilization cannot occur.

These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side effects too. Other contraceptive devices such as the loop or the copper-T are placed in the uterus to prevent pregnancy. Again, they can cause side effects due to irritation of the uterus. If the vas deferens in the male is blocked, sperm transfer will be prevented. If the fallopian tube in the female is blocked, the egg will not be able to reach the uterus. In both cases fertilization will not take place.

1. Contraceptive devices are meant for

1. Avoiding sex
2. Avoiding pregnancy
3. Surer methods of pregnancy
4. Termination of pregnancy.

Answer: 2. Avoiding pregnancy

2. Condom is

1. Barrier method of contraception
2. Intrauterine device for preventing pregnancy
3. Hormone based contraceptive
4. SAvoiding pregnancy

Answer: 1.  Barrier method of contraception

3. Pills are meant for

1. Change in hormone balance
2. Non-release of egg
3. Non-implantation of egg
4. Non-fertilization of egg.

Answer: 2. Non-release of egg

4. Copper-Tis

1. Intrafallopian device
2. Intravaginal device
3. Intrauterine device
4. Oral contraceptive.

Answer: 3. Intrauterine device

5. The surgical method for contraception in males Is the blocking of

1. Vas referential
2. One vas deferens
3. Both the vasa deferentia
4. Urinogcnital duct

Answer: 3. Both the vasa deferentia

6. Which one is blocked in females for contraception?

1. Cervix
2. Uterus
3. One fallopian tube
4. Both the fallopian tubes.

Answer: 4. Uterus

Class 10 Biology Notes For Components Of Ecosystem Food Chains And Webs

How does the food prepared by green plants or stored in dead matter move in a series of organisms feeding on one another?

Trophic Levels

They are levels in the biotic community at which organisms obtain their food.

biotic components and abiotic components

1. First Trophic Level (T1). It is the level of food manufacturers or producers which prepare food from inorganic raw materials with the help of solar energy.
2. Second Trophic Level (T2). It is the level of herbivores or primary consumers which directly feed on plants or plant parts.
3. Third Trophic Level (T3). It consists of primary carnivores or secondary consumers which prey upon herbivores.
4. Fourth Trophic Level (T4). It is the level of secondary carnivores or tertiary consumers which feed on primary carnivores.
5. Fifth Trophic Level (T5). It consists of tertiary carnivores which prey upon secondary carnivores.

Food Chains

A food chain is a sequence of trophic levels through which food passes in a biotic community from producers to ultimate carnivores. Here, members of one trophic level become food for members ofthe next trophic level.

Actually food chain is a summary of who eats whom. A food chain may have 3-5 trophic levels. It is rarely more. The various steps of a food chain are producers and various categories of consumers.

1. Producers. They constitute the first trophic level (T1) or base of a food chain. Producers manufacture organic food from inorganic raw materials with the help of solar energy. The major producers are plants in terrestrial ecosystems and phytoplankton in aquatic ecosystems.
2. Herbivores. They constitute the second trophic level (T2). Herbivores feed on plants or plant parts, for Example caterpillars, grasshoppers, deer, rabbits, mouse.
3. Primary Carnivores. They belong to the third trophic level or T3. Primary carnivores or secondary consumers feed on herbivores, Example Frog, Fox.
4. Secondary Carnivores. They are generally large-sized carnivores that belong to the fourth trophic level or T4. They prey upon primary carnivores, Example Hawk. Kingfisher.

Terrestrial Food Chains

1. Three Steps Forest Food Chain
   Plants →Deer →Lion
   (producers) (herbivores) (carnivores)
2. Four Steps Grassland Food Chain
   Grass →Insects →Insectivorous Birds→ Hawk
   (producers) (herbivores) (carnivores 1) (carnivores 2)
3. Five Steps Grassland Food Chain
   Grass→Insects → Frog →Snake→ Hawk
   (producers) (herbivores) (carnivores 1) (carnivores 2) (carnivores 3)

what are the major components of ecosystem

Aquatic Food Chains

1. Four-Step Pond Food Chain

Aquatic →Plants Crustaceans→ Fish →King Fisher
(producers) (herbivores) (carnivores 1) (carnivores 2) (carnivores 3)

2. Five-Step Ocean Food Chain

Phytoplankton →Zooplankton →Small fish →Larger fish →Shark
(producers) (herbivores) (carnivores 1) (carnivores 2) (carnivores 3)

Ecological Pyramids

Ecological pyramids (Elton 1927) arc graphic representations of different ecological parameters like number, biomass, and energy arranged successively with producers at the base, herbivores above them, followed by primary carnivores and top carnivores at the top. The quantity is indicated by the length of the box. It is also written in figures.

Pyramid of Numbers. It is a graphic representation of the number of individuals in a unit area sequence-wise with producer the base, herbivores above them, carnivores L carnivores successfully above them. Only very few top carnivores are supported by a producer population of millions of grassland.

major components of ecosystem

Pyramid of Biomass. It is a graphic representation of biomass or living organic matter present per unit area sequence-wise with producers at the base, herbivores above them followed by carnivores in various categories. Maximum biomass is present in producers. It decreases stepwise with the rise in trophic level.

Pyramid of Energy. It is a graphic representation of energy contained per unit area in various trophic levels with producers at the base, herbivores above them followed by carnivores. Maximum energy is contained in producers with a minimum in the top carnivores.

Flow of Energy and Ten Percent Law

In any ecosystem the flow of energy is unidirectional. Producers obtain energy from sunlight. About 1% of solar energy falling on leaves is changed into organic food. From here the food energy’ passes into herbivores. Herbivores cannot pass back the energy’ to producers nor do the producers pass back energy into the environment.

Lindeman (1942) found that during the transfer of energy from one trophic level to the next higher trophic level only 10% of energy is transferred. 90% of energy is lost in transfer, digestion, respiration, and other body activities. It is lost to the environment. The phenomenon is called the 10% law.

Because ofthe large amount of energy lost at every’ transfer, energy reaching higher trophic levels becomes small. Because the number of top carnivores is always small.

Suppose 1 million Joules of solar energy falls on producers. Producers have 1% efficiency, i.e., they will trap 10,000 Joules of energy in organic food. Herbivores will store 1000 Joules of food energy at 10% efficiency, primary carnivores 100 Joules of food energy while secondary carnivores shall have only 10 Joules of food energy.

Because of the smallness of food energy available at higher trophic levels, both the number of trophic levels as well as members of higher trophic levels will be small.

Biological Magnification (Biomagnification)

What is the phenomenon responsible for the increase in the concentration of persistent chemicals with the rise in trophic levels?

It is an increase in the concentration of persistent soluble chemicals with the rise in trophic levels.

Toxic chemicals are sprayed over crops to protect them from pests and pathogens. They are also sprayed in homes and commercial places to kill insects, mosquitoes, flies, and cockroaches.

Anumberoftoxic chemicals and heavy metals are also released by industries. All these enter waterbodies, soil, groundwater, and then plants. From plants, the persistent chemicals pass into herbivores and from them to carnivores.

Since there is regular entry ofthe chemicals in the food chain, their concentration increases with time in each trophic level. They prove harmful and even fatal to higher trophic-level animals.

Man is also harmed to a great extent as he obtains these chemicals from several sources- water, plant food, milk and meat An example of biomagnification is the study of the concentration of DT in water and the food chain.

Water→Plankton →Small Fish →LargerFish →Fish Eating Birds
0.003pm 0.04 ppm  0.5ppm        2.0ppm                25ppm

The population of fish-eating birds declined in the 1960s due to it. DDT as a pesticide has been banned since then. However, there are several other persistent and toxic chemicals.

Activity 5.5 Pesticide Levels in Food Items and Beverages

Readymade food items and beverages have been found to contain pesticide traces in the past. Many states had to ban the sale of such food items and beverages.

The pesticides are present in the groundwater as well as inside the plant products because they are used to protect the plants from pests.

The sprayed pesticides enter the soil, groundwater as well as water bodies besides the plants and their products. Therefore, beverages and readymade food items prepared from such groundwater as well as plant produce shall contain traces of pesticides.

Farmers must switch over to organic farming where pesticides are not sprayed. Buildings must be provided with double doors. Industries must have safety measures to control pollution.

Food Web

It is a network of several food chains present in an ecosystem where they get interconnected at various trophic levels. It makes each food available to several populations and a population capable of feeding on several foods.

In a food web rabbits can be eaten by foxes, wildcats, wild dogs, jackals, wolves, and hawks. Hawk can feed on snakes, rabbits, and several types of birds. Therefore, in the food web, no consumer is dependent upon a single type of food.

It does not get starved if its favorite food is in short supply. Similarly, if an organism becomes overpopulated, it will be noticed more by predators and therefore, eaten more in number.

On the other hand, an endangered species will not be eaten to a large extent. It will get the opportunity to recover. Thus, the food web is a mechanism for maintaining the stability of an ecosystem.

Question 1. What are trophic levels? Give an example of a food chain and state the different trophic levels init?
Answer: Trophic levels are levels in the biotic community at which organisms obtain their food. The food chain is the sequence of trophic levels through which food passes in a biotic community from producers to ultimate carnivores. A typical grassland food chain consists of the following trophic levels.

Grass →Insects →Insectivorous birds →Hawk
(producers) (herbivores) (carnivores 1) (carnivores 2)

Question 2. What is the role of decomposers in the ecosystem?
Answer: Decomposers are microscopic saprophytes like many bacteria and fungi, which feed on organic remains and organic excretions. They pour digestive enzymes over the organic matter for its simplification and solubilization.

The process releases many inorganic nutrients previously trapped in organic matter. The process is called mineralization. The soluble simple organic substances are picked up by decomposers for their growth. The released minerals become available to plants for their growth and manufacture of food.

Class 10 Biology Notes For Components Of Ecosystem Our Environment Multiple-Choice Questions

Question 1. In an ecosystem, 10% of energy available for transfer from one trophic level to the next is in the form of

1. Heat Energy
2. Chemical energy
3. Mechanical energy
4. Light energy

Answer: 2. Chemical energy

Question 2. Soil fertility is determined by its ability to

1. Decay organic matter
2. Hold organic matter
3. Hold water
4. Support life

Answer: 4. Support life

Question 3. A food web is constituted by

1. Relationship between the organisms and the environment
2. Relationship between plants and animals
3. Various interlinked food chains in an ecosystem
4. Relationship between animals and the environment

Answer: 3. Various interlinked food chains in an ecosystem

Question 4. How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores?

1. 100%
2. 10%
3. 1%
4. 0.1%

Answer: 2. 10%

Class 10 Biology Notes For Components of Ecosystem Our Environment Short Answer Type Questions

Question 1. Construct an aquatic chain showing four trophic levels.
Answer: Algae → Crustaceans → Small Carnivorous Fish → Large Carnivorous Fish.

Question 2. Explain biological magnification with the help of an example.
Answer: Biological magnification or biomagnification is the increase in the concentration of a soluble but persistent chemical per unit weight of an organism with the rise in trophic level. A study on DDT concentration has given the following data.

Water → Plankton → Small Fish → Large Fish → Fish Eating Birds 0.003 ppm 0.04 ppm 0.5 ppm 2.0 ppm 25 ppm

Question 3. Observe the food chain: Plant (1000 J) → Goat → Lion.

1. If autotrophs occupy the first trophic level and are called producers what are herbivores called?
2. How much energy does the Lion get in the above chain?

Answer:

1. Herbivores are primary consumers.
2. As per the 10% law, 1000 J of energy in plants is transferred as 100 J of energy in goats and only 10 J in Lions.

Question 4. The maximum concentration of harmful chemicals accumulates in human beings. State the phenomena involved and justify this statement.
Answer: Biological magnification Human beings are omnivorous. They live at the top of every type of food chain. Harmful chemicals enter the human body through groundwater, plant produce, milk, eggs, and meat. They remain in the human body and continue to accumulate. As a result, the maximum concentration of harmful chemicals occurs in human beings.

Question 5. In the food chain, (Grass → Deer→ Lion), operating in a forest what will happen if all the (a)Lions are removed (b) Deer are removed?
Answer:

Removal of lions will result in a rapid increase in the population of deer. The rise in deer population will ultimately result in the eating of the whole grass and desertification of the area. This will cause the death of deer.

The removal of deer will result in excessive growth of grass but no food for lions. As a result, lions will die.

Question 6. List two reasons to show that the existence of decomposers is essential in an ecosystem.
Answer:

1. Decomposers feed on organic remains and cleanse the earth of the same.
2. They release minerals from organic remains that are utilized by plants for the synthesis of organic matter.

Question 7. A food web is shown as a series of branching lines of food chains. Explain and justify the statement.
Answer: The food web is a network of many food chains that get connected at different trophic levels so that several alternate feeding connections develop amongst the organisms. These alternate feeding connections appear as branching lines of the food chains.

Question 8. Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment.
Answer: Bacteria and fungi are called decomposers as they bring about the degradation of organic remains. For this, they secrete digestive enzymes over the organic remains. The enzymes convert complex substances into simple and soluble substances. The latter are used as food by the decomposers. During this decomposition, the inorganic nutrients forming part of organic matter are released.

Advantages: Decomposers cleanse the earth of organic remains. They bring about the release of inorganic nutrients which become available for recycling.

Question 9. What is an ecosystem? List its main components. We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Explain.
Answer:

Components of Ecosystem, Biotic components are producers, consumers, and decomposers. Abiotic components are climate, soil, topography, inorganic nutrients, and organic remains.

An aquarium is an incomplete and imbalanced artificial ecosystem that lacks producers, food chains, and decomposers. There is no self-cleaning as occurs in ponds or lakes.

Question 10. “Our food grains such as wheat and rice, vegetables, fruits, and even meat are found to contain varying amounts of pesticide residues.” State the reason to explain how and why it happens.
Answer: Cereals, vegetable, and fruit crops are sprayed with pesticides to protect them from pests. These pesticides not only enter the crop plants but also pass into soil, groundwater, and nearby water bodies. Animals drinking the contaminated water and eating pesticide-containing fodder will also come to have the pesticides. Therefore, green vegetables, fruits, and meat will have varying amounts of pesticides.

Question 11. “Energy flow in a food chain is unidirectional.” Justify this statement.
Explain how the pesticides enter the food chain and subsequently get into our bodies.
Answer:

Energy from the sun enters the food chain at the level of producers. The efficiency is 1%. From producers energy (as food energy) passes to herbivores. The efficiency is 10%. The rest of the energy is dissipated in transfer, digestion, and respiration.

Primary carnivores similarly can retain only 10% of the energy obtained from herbivores. Because ofthe regular dissipation of energy at every step and decrease of energy with the rise in trophic level, energy cannot flow back. Thus, its flow is unidirectional from

Sun→producers → herbivores → primary carnivores→ secondary carnivores.

Pesticides are sprayed over crops to protect them from pests. They enter the plants, soil, vegetation, groundwater, and water bodies and hence all types of food chains and from there to humans as man is a consumer of water, crop products, milk, eggs, meat, etc. all of which get contaminated with pesticides.

Question 12. How do pesticides spray over crops and fruit plants enter our bodies and accumulate? Name the phenomenon by which their concentration increases in our body.
Answer: Pesticides sprayed over plants enter their bodies and reach their edible parts. They also seep into the ground and contaminate groundwater. Groundwater also enters plants and further contaminates them.

From vegetables, fruits, other edibles, and groundwater pesticides regularly enter the human body and accumulate. They also enter the food chains which pass the same to human beings. Accumulated pesticides become highly toxic and cause harm to vital organs.

The increase in the concentration of non-biodegradable substances with time and with the rise in trophic levels is called biomagnification.

Question 13. Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.
Answer: Ecosystem. It is a self-sustained segment of nature that has a biotic community and abiotic components of the environment both interacting and exchanging materials between them.

Question 14. Define a food chain. Design a food chain of four trophic levels. If a pollutant enters at the producer level, the organisms of which trophic level will have the maximum concentration of the pollutant in their bodies. What is the phenomenon called?
Answer: Food Chain. It is a sequence of trophic levels through which food passes in the biotic community from producers to ultimate consumers. It is also called the series of eating and being eaten.

Maximum Concentration of Pollutant. Members of the highest trophic level have the maximum concentration of pollutants. The phenomenon of a rise in the concentration of nonbiodegradable pollutants with the rise in trophic levels is called biomagnification.

Question 15.

1. Construct a terrestrial food chain comprising four trophic levels.
2. What will happen if we kill all the organisms at one trophic level?
3. Calculate the amount of energy available to the organisms at the fourth trophic level if the energy available to the organisms at the second trophic level is 2000 J.

Answer:

1. Grass → Insects → Frog → Snake.
2. If all the organisms of one trophic are killed (/) The animals of higher trophic levels will starve and die Organisms of the lower trophic level will increase.
3. 2nd Trophic level → 3rd Trophic level → Fourth Trophic Level

⇒ \(2000 \mathrm{~J}{10 \%} 200 \mathrm{~J} {10 \%} 20 \mathrm{~J} .\)

Question 16. What are decomposers? List two consequences of their absence in the ecosystem. 
Answer: Decomposers. They are microscopic organisms like many bacteria and fungi that break down complex components of organic remains and excretions into simpler forms releasing minerals in the process.

Consequences of Their Absence. Organic remains and excretions will pile up (it) There will be no recycling of minerals and other nutrients in nature.

Question 17.

1. From the following group of organisms, create a food chain that is the most advantageous for human beings in terms of energy Hawk, Rat, Cereal plant, Goat, Snake, Human beings
2. State the possible disadvantage if the cereal plant is growing in soil rich in pesticides.
3. Construct a food web using the organisms mentioned above.

Answer:

1. Cereal Plants→ Human Beings.
2. Pesticides enter the cereal plants and undergo accumulation with the rise of trophic levels as they are non-biodegradable. The phenomenon is called biomagnification.

Question 18.

1. Define ecosystem.
2. Autotrophs are at the first level of the food chain. Give reason.
3. In a food chain of frogs, grass, insects and snakes assign trophic levels to frogs. To which category of consumers do they belong?

Answer:

• Only autotrophs can manufacture food and transfer this food and its energy to the next level of the food chain.
• Grass→Insects→Frogs→Snakes
• Primary consumer Secondary consumer Tertiary consumer

Question 19.

1. State the reason for the consequence of the decrease in the number of carnivores in an ecosystem.
2. In a food chain, state the trophic level at which the concentration of harmful chemicals is maximum.
3. Why is it so?

Answer: (cr) Decrease in carnivores will increase the number of herbivores being their prey.

Top carnivores. The harmful chemicals are non-biodegradable. They accumulate in higher qua rise in trophic level.

Question 20. What is meant by trophic level in a food chain? The energy flow in a food chain is
Answer: Trophic Level. It is the level in the biotic community at which a particular group of organisms obtain Energy flow.

Question 21. Complete the following flow chart based on the ecosystem and its components

Answer:

1. Aquatic,
2. Abiotic
3. Air, water, soil, temperature, light.
4. Plants and animals.

Question 22.

1. Create a food chain of insects, hawks, Grass, snakes, and frogs.
2. Name the organism at the third trophic level.
3. Which organism will have the highest concentration of non-biodegradable chemicals?
4. Name the phenomenon associated.
5. If 10,000 joules of energy are available to frogs, how much energy will be available to snakes

Answer:

1. Grass Insect Nake Hawk.
2. Frog,
3. Hawk
4. Biomagnification
5. 1000 joules (10,000/10).

Question 23. What is an ecosystem? List any two natural ecosystems.
We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Why
Answer: Pond ecosystem, Forest ecosystem.

Question 24. In the following food chain, only 2J of energy was available to peacocks. How energy would have been present in the grass? Justify your answer. Grass→Grasshopper→ Frog → Snake→Peacock
Answer: Transfer of energy from the lower to the next higher trophic level follows the 10% law. 2 J energy in a peacock ha from 20 J energy of a snake. 20 J energy of the snake has been obtained from the 200 J energy of the frog.

Frog gets this much energy from the 2000 J (200 x 10) energy of a grasshopper. 2000 J energy of grasshopper has come from 20,000 J (2000 x 10) energy of grass.

Question 25.

1. What is meant by garbage? List two classes into which garbage is classified.
2. What do we mean when we say that the “enzymes are specific in their action”?

Answer: Garbage is rubbish formed of mostly household waste and similar waste from vegetable and fruit markets as well as food industries, Example food left-over, spoiled food, vegetable and fruit peels, tea leaves, milk powder, polythene bags, wrappers, broken crockery, paper waste clothes, waste plastic and metallic articles.

Garbage consists of two types of waste, biodegradable and non-biodegradable. Biodegradable Garbage.

It is garbage that gets decomposed naturally by microbes, for Example, vegetable and fruit peels, food leftovers, paper, etc. Nonbiodegradable Garbage. It is garbage that cannot be disposed of by microbes, for example, broken crockery, plastic, and metallic wastes.

Enzymes are specific for various substrates. They require a particular pH temperature for their activity.

Question 26.

1. Human beings are most adversely affected by biological magnification. State the reason.
2. Why can ordinary washing of edibles (fruits and vegetables) not reduce the effect of biological magnification?

Answer: Biological magnification is the increase in the concentration of non-biodegradable or persistent chemicals with the rise in trophic level.

As human beings occupy the top position in various food chains, they receive the maximum concentration of these chemicals. Being long-lived, the harmful chemicals accumulate in the human body and cause toxic effects.

Washing vegetables and fruits can remove harmful chemicals from their surface. However, it cannot remove nonbiodegradable chemicals as they occur inside the food items.

Question 27.

1. What are trophic levels in a food chain?
2. Explain the flow of energy through the food chain.
3. Write a four-trophic level food chain.

Answer:

1. Trophic Levels. They are levels in the biotic community at which organisms obtain their food. Producers constitute the first trophic level (T1), herbivores the second trophic level (T2), primary carnivores the third trophic level (T3), and so on.
2. Flow of Energy Through Food Chain.
3. Grass →Insect →Insectivorous bird→Hawk.

UP Board Class 10 Biology For How Do Our Activities Affect The Environment

India today is facing the problem of overuse of resources, contamination of water and soil, and lack of methods of processing waste. The time has come for the world to say goodbye to “single-use plastics”.

Steps must be undertaken to develop environment-friendly substitutes, effective plastic waste collection, and methods of disposal. Indore treated 15 lakh metric tonnes of waste in just 3 years, through biomining and bioremediation techniques.

Bioremediation involves introducing microbes into landfills to naturally ‘break’ it down. Biomining involves using trommel machines to sift through the waste to separate the ‘soil’ and the waste component.

The city managed to chip away 15 lakh metric tonnes of waste at the cost of around < 10 crore. A similar experiment was successfully carried out in Ahmedabad also.

effects humans have on the environment

Question 1. What is ozone and how does it affect any ecosystem?
Answer: Ozone is a molecule formed by three atoms of oxygen O3. Normal oxygen is 02 or formed of two atoms. Ozone is toxic if present in the lower atmosphere or troposphere.

It destroys the photosynthetic cells of plants and causes injury to mucous membranes, eye irritation, and internal hemorrhage. However, ozone present in the stratosphere is highly useful.

It protects the ecosystem from harmful UV radiations (UVC 100 – 280 nm, UVB 280 – 320 nm) by dissipating their energy. In case of ozone depletion, there would be a rise in skin cancers, cataracts, photobombing, a decrease in immunity, a fall in photosynthetic efficiency, and death of larvae.

Question 2. How can you help in reducing the problem of waste disposal? Give any two methods.
Answer: The following two methods can help in reducing the problem of waste disposal:

1. Recyclable Waste. It should be separated from the rest ofthe garbage. Recyclable waste includes paper, cardboard, polythene, plastic, glass, metallic cans, etc. They are picked up by rag pickers for selling them to factories for recycling.
2. Nonrecyclable Biodegradable Waste. It includes stale food, leftover food, vegetable peelings, fruit peelings, used tea leaves, prunings of the kitchen garden, etc. It can be converted into compost for your kitchen garden, or school garden or handed over to municipal waste disposal workers.

UP Board Class 10 Biology For How Do Our Activities Affect The Environment Short Answer Type Questions

Question 1. What is ozone? How does it protect the organisms on the earth?
Answer: Ozone is a triatomic molecule that is formed by three atoms of oxygen, 03. Ozone present in the stratosphere filters out harmful high-energy UV radiations and thus protects the organisms on the earth from them.

Question 2. We often observe domestic waste decomposing in the by-lanes of residential colonies. Suggest ways to make people realize that the improper disposal of waste is harmful to the environment
Answer: Domestic waste is often thrown outside each home or at one corner of the street. This attracts pigs, stray cattle, and dogs who scatter the waste that starts decomposing and emitting a foul smell. The practice is unhygienic. Domestic waste must be segregated and the segregated waste must be lifted by municipal staff.

Question 3. Explain how ozone is formed in the atmosphere. How does it protect living beings from harmful radiations of the sun?
Answer: Ozone is formed in the stratosphere from O₂ by the action of energy UV radiations.

⇒ \(\begin{gathered}
\mathrm{O}_2 \xrightarrow{\mathrm{UV}}[\mathrm{O}]+[\mathrm{O}] \\
\mathrm{O}_2+[\mathrm{O}] \longrightarrow \mathrm{O}_3 \text { (ozone) }
\end{gathered}\)

Ozone present in the stratosphere also dissipates the energy of harmful UV radiation. The latter, therefore, do not reach the earth.

how do humans affect the environment

Question 4. Why is the Government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment.
Answer: Polythene is non-biodegradable. Discarded polythene bags choke drains, kill animals feeding on garbage, and pile up. They are being replaced by cloth/jute and paper bags. Cloth/jute bags can be used again and again. Along with paper bags, they are biodegradable.

Question 5. Recycling of paper, metal, plastic, and e-waste is done in most places. Mention the positive impact of this recycling process on the environment.
Answer: There will be less exploitation of resources in forming newer articles.

There will be less pollution as the recyclable articles are picked up as soon as they are discarded.

Question 6. It is said that there is a need to put a complete ban on the products containing aerosols. What are aerosols? Why is there a demand to ban them?
Answer: Aerosols are propellant gases that are used to release substances such as a fine spray, for Example perfumes, and deodorants. The gases used to be chlorofluorocarbons. Since they have strong ozone-depleting properties, there clamor for banning them. Chlorofluorocarbons have now been replaced by isobutene or methyl propane.

Question 7. In order anto individual so ? can contribute by becoming environmentally friendly. What practice
Answer:

1. Use repeatedly reusable cloth bags instead of polythene bags.
2. At home separation of biodegradable and nonbiodegradable wastes.
3. Employment of containers used in packing at home, instead of throwing them after taking out the contained edibles.

Question 8. Damage to the ozone layer is a cause of concern.” Justify the statement. Suggest any two steps to limit this damage.
Answer: The ozone layer present in the stratosphere has thinned out by more than 8%. It has resulted in a 15-20% increased penetration of harmful UVB radiations reaching the earth.

They are causing increased skin cancers, snow blindness, cataracts, a fall in immunity, reduced photosynthesis, and a higher number of mutations.

Steps to Limit Damage:

1. Stoppage of the use of chlorofluorocarbons.
2. Stoppage of the use of halons.
3. Replacing the ODS with safer chemicals.

human impact on the environment activities

Question 9. List 2/3 changes in habits that people must adopt to dispose of non-biodegradable waste to save the environment.
Answer:

1. Use of cotton and jute bags for shopping.
2. Segregation of household waste into biodegradable and non-biodegradable and placing them in separate bins.
3. Adoption of three ‘Reduce, reuse, and recycle.

Question 10. Suggest two measures to manage the garbage we produce.  =As an individual what can be done to generate the least garbage? Give two points.
Answer:

Management of Garbage.

1. Separation of garbage into biodegradable and nonbiodegradable, recyclable, and nonrecyclable portions.
2. Handing over the recyclable garbage to rag pickers, and others to waste collectors.

Generate No Garbage.

1. Use cloth bags or jute bags for shopping. Say no to polythene or plastic bags.
2. Reuse glass and metallic containers instead of throwing them.

Question 11. How is ozone formed in the upper atmosphere? State its importance. What synthetic chemicals are responsible for the drop in the amount of ozone in the upper atmosphere? How can the use of these chemicals be reduced? Write one harmful effect of ozone depletion. Why did the amount of ozone in the atmosphere drop sharply in the 1980s?
Answer: Ozone is formed in the upper atmosphere or stratosphere from 02 by the action of high energy UV radiations

⇒ \(\begin{aligned}
& \mathrm{O}_2 \xrightarrow{\mathrm{UV}}[\mathrm{O}]+[\mathrm{O}] \\
& \mathrm{O}_2+[\mathrm{O}] \longrightarrow \mathrm{O}_3 \text { (ozone) }
\end{aligned}\)

Ozone present in the stratosphere dissipates the energy of harmful UV radiations ( 1 00-320 nm). The latter, therefore, do not reach the earth.

However, certain synthetic and other chemicals destroy the same, for example chlorofluorocarbons, and halons. They are called ozone-depleting substances (ODS). To the ozone layer, the use of ODS has to be reduced and leakage of these substances prevented.

Alternative chemicals that do not harm the ozone are being searched to replace the ODS. Cb) Release of ozone-depleting substances like CFCs from refrigerators, air conditioners, foam manufacturing industry, fire extinguishers, and aerosols. Harmful Effect of Ozone Depletion. Skin Cancer, Snow blindness.

how human activities affect the environment

Question 12. Complete the following table

Answer:

1. O₂
2. O₃.
3. Breathing
4. Absorbs harmful UV radiations.

Question 13. Kulhads (disposable cups made of clay) and disposable paper cups, both are used as alternatives to disposable plastic cups. Which one of these can be considered a better alternative to plastic cups and why?
Answer: Disposable paper cups are a better choice as they are biodegradable and do not harm the ecology. Kulhads which are made of clay deprive the fields of their fertile topsoil.

Question 14. Why is the ozone layer getting depleted at the higher levels of the atmosphere? Mention harmful effects caused by its depletion.
Answer: The ozone layer present in the upper atmosphere has been getting depleted due to synthetic chemicals emanating from the earth, viz. chlorofluorocarbons (used in refrigeration) and halons used in fire extinguishers). They release chlorine which reacts with ozone breaking it into oxygen. Harmful Effect. More UV radiation reaches the earth. They cause skin cancer.

Question 15 What are decomposers? State the role of decomposers in the natural replenishment of the soil. Why are decomposers not helpful in decomposing plastic waste?
Answer: Decomposers do not possess enzymes for digestion on the breakdown of plastics

Question 16. State two methods of effective plastic waste collection in your school.
Answer: Use separate bins for recyclable waste, plastic waste, and biodegradable waste.

effects of human activities on environment

Question 17. Name any two uses of “single-use plastic” in daily life.
Answer:

• Packaging of water, milk, food, biscuits, etc.
• Formation of disposable articles like bowls, tumblers, plates, forks, spoons, etc.

Question 18. If we discontinue the use of plastic, how can an environmentally friendly substitute be provided?
Answer: Use thick glazed paper, jute or cloth, cardboard, metallic utensils, and earthen pots.

Question 19. Do you think microbes will work similarly in landfill sites as they work in the laboratory? Justify your answer.
Answer: Yes, microbes will work similarly in laboratory and waste dumps provided the conditions of the two are similar.

UP Board Class 10 Biology For How Do Our Activities Affect The Environment Long Answer Type Questions

Question 1.

1. What is ozone? How is it formed in the atmosphere? Explain with equations.
2. How is the ozone layer useful?
3. Name the substances responsible for the depletion of the ozone layer.

destruction of the environment

Answer: Chlorofluorocarbons (CFCs), halon, carbon tetrachloride, methyl; chloroform, methyl bromide, bromochloromethane.

UP Board Class 10 Biology Notes For Control And Coordination

Control is the faculty to regulate an activity, start it, slow down it, expedite it, or stop it. Coordination is the orderly working of different parts to smoothly carry out an activity.

• For example, during the eating of food, the nose smells it, saliva moistens the food, teeth masticate it and the tongue tastes it as well as moves it for mastication and swallowing.
• However, if the nose is blocked due to a bad cold, the food will appear bland or tasteless showing the requirement of coordination between smell and taste.
• Major controls and coordination are achieved through movements. Movements or changes in position are of two types-growth movements and nongrowth movements.
• Growth movements mostly occur in plants, for example., sprouting of seed to form seedlings. Animals perform mostly nongrowth movements, for example., running, playing, buffalo chewing cud, and shouting.
• Plants also perform many non-growth movements for example., folding and drooping of leaves in Sensitive Plant on being touched.
• Movements usually occur in response to changes in the external or internal environment. They are carefully controlled and coordinated. For example, while talking to your classmates in the class you whisper. In the playground, you shout at your classmates.
• In multicellular organisms, control and coordination are achieved using specialized tissues and organs. In animals, this is performed by nervous tissue and muscular tissue.

Additional control and coordination are achieved through the endocrine system. In plants, only the endocrine system operates in control and coordination.

control and coordination class 10

UP Board Class 10 Biology Notes For Control And Coordination Animals Nervous System

What is the system to detect information from the environment? What are receptors?

The nervous system is a system of nervous organs, nerves, and a network of electrically conducting neurons that runs throughout the body of the animal for controlling and coordinating body activities. Body activities are performed in response to internal and external stimuli.

• Stimulus is a detectable change in environment, factor, agent, or chemical that brings about a response in the organism.
• The response is the specific reaction of an organism to a specific stimulus.
• Receptors are cellular structures that are capable of receiving specific stimuli and generating impulses to be picked up by sensory or afferent nerves.
• An impulse is an electrical signal that travels along the length of nerve fiber for the passage of information.
• Effectors are muscles, glands, cells, tissues, or organs that respond to a stimulus received through nerve impulses. The message to effectors is sent through motor or efferent nerves.
• Sense and Sense Organ. The faculty by which an organism perceives the change in external or internal environment is called sense, for example., smell, hearing, touch.
  • The organ which contains sensory receptors for obtaining information about the environment is called a sense organ, for example., the eye, or ear.
  • In humans and higher animals, there is the brain that functions as a super center for the control and coordination of various activities. The basic unit of the nervous system is neurons or nerve cells.

Neuron or Nerve Cell

A neuron or nerve cell is the structural and functional unit of the nervous system. It can receive, conduct, and transmit impulses. Neurons appear like miniature branched trees.

It can reach a length of 90-100 cm. A neuron has three parts body, dendrites, and axon. Dendrites and axons are collectively called neurites.

1. Cell Body (Cyton). It is the widest part of neuron which is polygonal with a stellate outline. There is a prominent centrally located nucleus, various cell organelles (except centrosome), and two special structures, Nissl granules and neurofibrils. Nissl granules are ribosomes containing particles. Neurofibrils are cytoskeletal fibrils (microtubules, microfilaments, and neurofilaments).
2. Dendrites. They are short, fine, branched, protoplasmic outgrowths of the cell body. Nissl granules and neurofibrils are present. Dendrites pick up sensations and transmit the same to the cell body.
3. Axon. It is a long fiber-like process of the cell body that is specialized to carry impulses away from the cell body. It contains neurofibrils but lacks Nissl granules. Axon is branched terminally to form knobbed ends called boutons. They are meant for transmission of impulses to another neuron, cell, gland, muscle, or organ.

Axon is covered by one or two sheaths. The ensheathed axon is known as a nerve fiber. The single or the outer sheath is called neurilemma (= neurolemma).

• It is made up of Schwann cells. When two layers are present, the inner layer is made of lipid or myelin. Such nerve fibers are called myelinated or medullated.
• At intervals, nonmyelinated areas occur. They are called nodes of Ranvier. Myelinated or medullated nerve fibers are more efficient in the transmission of impulses than nonmedullated ones.

” coordination class 10″

Types Of Neurons

• Depending upon the Impulne enameled motor or Inlerneuron, Scnnory or account lemon picks up Nenmny Impulse iVom lorcplt^i or sense organ and immimilii llm same towards brain or spinal cord.
• Motor or efferent neuron carries a message from the brain or spinal cord to muscle, gland, organ, or other effector.

Nerves

What is a nerve? Name different types of nerves.

• They are elongated thread-like structures of the nervous system which are formed by grouping and regrouping of nerve fibers inside the sheath of connective tissue.
• Connective tissue sheaths keep the nerve fibers insulated from one another. Like neurons, based on their functioning, nerves are of three types -sensory, motor, and mixed. Mixed nerves contain both sensory and motor fibers.

Differences between Sensory and Motor Nerve Fibres

Transmission of Nerve Impulse

Define impulse. Name the chemical that helps in the transmission of impulses.

An impulse is a self-propagated electrical signal that travels along the length of the neuron for the passage of a message. At rest, a neuron is polarized with a positively charged exterior and a negatively charged interior.

• As soon as it receives a stimulus, the neuron region undergoes depolarisation with the outer surface becoming negatively charged and the inner surface becoming positively charged. This happens due to the opening of ion channels causing entry of Na+ ions inside the nerve.
• The depolarized region functions as a local current or stimulus which depolarises the next part of the nerve while itself becoming polarised. The process continues till the impulse reaches the end of the neuron.
• From here impulse jumps to the next neuron, muscle, or other ‘target organ with the help of chemicals (for example.,. acetylcholine) called neurotransmitters.

Synapse

It is a narrow communicating junction between two neurons. The axon terminal of one neuron forms a presynaptic Knob. The dendrite tip of the next neuron is expanded but depressed to form postsynaptic depression.

• The narrow space between the two is called the synaptic cleft. The presynaptic knob possessed a number of neurotransmitters containing synaptic vesicles.
• The remembrance of the postsynaptic depression possesses several chemoreceptor sites.

As the impulse reaches the presynaptic knob, it activates the synaptic vesicles. They reach the presynaptic membrane and burst open. Ncurotransmittcr (for example., acetylcholine) is released.

Neurotransmitter molecules come in contact with chemoreceptor sites of the postsynaptic membrane.

chapter 7 science class 10 ncert solutions

The latter becomes depolarized to generate an electric current or impulse. The impulse travels across the synapse only in one direction from the axon terminal to the dendrite tip.

Neuromuscular Junction

What is a neuromuscular junction? Give its function.

It occurs at the junction between the muscle (or some other effector organ) and the axon end of the motor neuron. The axon end bears a motor end plate of knobbed branches.

• A knob or bouton of the motor end plate comes in near contact with depression called a sole plate on the surface of the muscle fiber. As the motor impulse reaches the synaptic knob, it activates the synaptic vesicles.
• They come to the surface and burst releasing neurotransmitters (for example., acetylcholine). The neurotransmitter coming in contact with the sole plate receptors brings about excitation that causes the muscle to contract.

UP Board Class 10 Biology Notes For Control And Coordination Activity 2.1

Taste Vs Smell

Put some sugar in your mouth. It tastes sweet. Rinse mouth with water. Block your nose with your thumb and index finger. Put some sugar again in your mouth. There is very little sweetness indicating that our taste is largely governed by smell.

Nerve Actions

There are three types of nerve actions, involuntary and reflex, Voluntary nerve action is under the control or command of the brain, for example., talking, and writing.

what do you mean by control and coordination

• Involuntary nerve action operates without the command of the brain as per the requirement of sensation generated in internal organs, for example., peristalsis.
• Reflex action is nerve-mediated automatic mechanical and immediate response to a stimulus for protection and functional efficiency, eg., closing of eyes when strong light is flashed over them, pulling of hand from a hot surface before the brain feels the pain.

UP Board Class 10 Biology Notes For Control And Coordination Long Answer Type Questions

Question 2. Mention the part of the brain involved in the following:

1. Walking in a straight line.
2. Picking up a pencil.
3. Blood pressure.
4. A question is asked by the teacher in the class.
5. Change in size of the pupil in response to the intensity of light.

Answer:

1. Walking in a straight line. Cerebellum.
2. Picking up a pencil. Cerebrum and cerebellum.
3. Blood Pressure. Medulla oblongata.
4. The question being asked by the teacher. Temporal lobe and frontal lobe of the cerebrum.
5. Changing pupil. Superior corpora quadrigemina of midbrain.

ch 7 science class 10 ncert solutions

Question 5.

1. Define nerve impulse. Name the structure that helps to conduct a nerve impulse
   1. Towards cell body
   2. Away from the cell body.
2. Why have organisms adapted to use electrical impulses to transmit messages? State two limitations of the use of electrical impulses.

Answer:

1. Nerve Impulse. It is a progressive electrochemical wave that develops in response to stimulus and travels along a nerve fiber to stimulate or inhibit the action of another nerve, muscle, or gland.
   1. Dendrite
   2. Axon.
2. Electrochemical impulses are very fast. There is no chance of spillover or after-effects. This allows the animal body to use the same nerve time and again.

Impulse Limitations.

1. Electrochemical impulse is unidirectional.
2. It is short-acting, also in the presence of stimulus only,
3. It does not reach every cell of the body,
4. After the generation and transmission of an electrical impulse, the nerve cell will take some time to receive and transmit a fresh electrochemical impulse.

UP Board Class 10 Biology Notes For Coordination In Plants

What are movements? How do they differ from locomotion? What are tropic movements?

Plants are devoid of nerves and muscles. They are fixed. Even then they show movements though locomotion is absent. These movements may be directional (tropic) or nondirectional (nastic), growth, or turgor-based.

• The movements are quite slow in most of the cases. It may take a few days to notice the change in position or movement. However, some turgor-based movements are quite fast and easily discernible.

Turgor-Based Plant Movements

• The plants have certain areas that have special cells that can shrink or swell with the loss or gain of water. They show reversible movements, for example., opening or closing of stomata, sleep movements of legume leaves, and drought-induced rolling of some grass leaves.
• Sleep movements of legume leaves are called nyctinasty. Drought-related rolling of grass leaves is called hydronasty.

UP Board Class 10 Biology Notes For Coordination In Plants Immediate Response To Stimulus

If you happen to touch a pinnule of Mimosa pudica (Sensitive Plant, Touch-me-not Plant, Shame Plant, Shy Plant) all the pinnules fold upwardly, the pinnae come together, and the whole leaf droops down.

• The place of stimulus is away from the area of movement. Further, it goes beyond the area of sensitization to other pinnae as well as to the whole leaf. Naturally, the stimulus travels from the area of contact to the area of response.
• This passage must be cell-to-cell like an electrical-chemical impulse or a chemical called turgorin. The differential movements are due to special cells at the base of pinnules, pinnae, and petiole that shrink on activation and later recover after about 10 minutes.
• As the movement in Mimosa is nondirectional, it is called nastic movement. The movement is due to touch or shock. It is, therefore, known as haptonasty or seismonasty.

plant movement

UP Board Class 10 Biology Notes For Coordination In Plants Growth Based Plant Movements

What are growth movements? Name its two types.

They are plant movements caused by differential growth or unequal growth in different parts of the organ. This results in bending and other types of movements. Growth movements are of two types, nastic and tropic.

• Nastic movements are non-directional. They are determined by the structure of the organ and not the direction of the stimulus, for example., the opening of flowers due to greater growth or epinasty on the upper surface of sepals and petals.
• Tropic movements occur in cylindrical organs. The direction of movement is related to the direction of the stimulus. Tropic movements are also called curvature movements.

movement due to growth class 10th

Differences Between Nastic And Tropic Movements

Depending upon the stimulus, tropic movements are of many types—phototropism, geotropism, hydrotropism, chemotropism, and thigmotropism.

1. Phototropism. It is tropic movement in response to uni-directional exposure to light. Stems generally bend towards the source of light.

• They are called positively phototropic. Leaves lie at right angles to the direction of light. They are diaphototropic. Roots are either neutral or negatively phototropic.
• In the stem, the stimulus of light is received by the stem apex. Leaves are essential for it. The region of response is a zone of elongation present below the apex. Blue light is effective in causing phototropism. The photoreceptor is a chemical called phototropin.
• The movement is caused by decreased availability of auxin on the illuminated side and more on the shaded side. The shaded side grows more resulting in bending movement.
• In the root where negative phototropic movement is observed, more auxin on the shaded side causes inhibition of growth (opposite to that of the stem).

Sunflower heads perform suntracking due to positive phototropism while plants growing in the open do not show bending movements as auxin diffuses uniformly in the growing region.

UP Board Class 10 Biology Notes For Coordination In Plants Activity 2.2

Demonstration Of Phototropism

Fix a wire mesh over the mouth of a conical flask full of water. Place one or two freshly germinated bean seeds on the mesh. Take a large cardboard open on one side.

• Place the flask in the cardboard kept near a window so that the seedling receives light from one side only. Observe after 2-3 days.
• The shoot has bent towards the source of light while the root has bent away from it. It shows that the stem is positively phototropic while the root is negatively phototropic.
• Now rotate the flask by 180° and observe after 3-4 days. The shoot and the root have developed curvatures and a new direction of bending by the young shoot towards the light and the young root away from light.

movements in plants

2. Geotropism. It is tropic movement or growth movement of curvature that occurs in response to the vector of gravity. Stems are generally negatively geotropic while roots are positively geotropic.

• Their branches are plagiogeotropic or lie at an angle to the direction of gravity. Stimulus of gravity is perceived by the stem apex, stem nodes, and root cap.
• It is because of the negative geotropic nature of the stem and the presence of receptor regions in the nodes that the lodged shoots become vertical.
• Negative geotropism helps shoots to properly expose themselves to sunlight.

Positive geotropism of roots helps them to fix the plant in the soil and absorb water as well as minerals from the same.

UP Board Class 10 Biology Notes For Coordination In Plants Activity 2.3

Demonstration Of Geotropism

• Place a potted plant horizontally on the ground. Provide support to the pot to prevent rolling. Regularly water the plant. Observe after a week.
• The apical part of the shoot has bent upwardly while the roots have bent downwardly. It shows that the stem is negatively geotropic while the root is positively geotropic.

3. Hydrotropism. It is tropic or directional growth movement of curvature that develops due to unilateral exposure to water. Hydrotropism is mostly seen in roots which are positively hydrotropic. Positive hydrotropic movement of roots is stronger and even overcomes their positive geotropic response.

movement of plants

UP Board Class 10 Biology Notes For Coordination In Plants Activity 2.4

Demonstration Of Hydrotropism

Take a sieve. Fill it with moist sawdust and support it on the sides over wooden blocks. Place a few soaked germinating seeds in the sawdust. Sprinkle water over the sawdust.

• Within 1-2 days radicles will be seen coming down from the pores of the sieve and hanging in the air.
• However, within a few hours, the radicle will be found to bend back and enter the wet sawdust showing that the positive hydrotropism of roots is stronger than that of their positive geotropism.

what is thigmotropism class 10

4. Thigmotropism. It is tropic or growth movement of curvature that occurs in tendrils and twiners in response to the stimulus of contact.

• As a tendril or twiner comes in contact with a support, it encircles the same. The reason is less growth in the region of contact and more growth on the free side.
• Here, contact causes less auxin production and hence less growth.

5. Cliemotropism. It is tropic or growth movement of curvature that occurs in plants in response to a chemical stimulus.

• The best example is the passage of the pollen tube through the style and inside the ovary towards the ovule where synergids are sending out chemical signals.

UP Board Class 10 Biology Notes For Coordination In Plants Chemicals Coordination In Plants

What arc phytohormoncs? Why they are called plant growth regulators?

Plants do not have nerves and muscles to coordinate their activities. Instead, they have chemical messengers or hormones.

• Plant hormones or phytohormones are non-nutrient diffusible chemical substances that can control various activities of plants like growth, differentiation, movements, development, and other physiological processes.
• For this, the target or effector cells possess receptors for picking up the hormones. Plant hormones are also called plant growth regulators (PGRs) as they function by promoting or inhibiting growth.
• Major plant hormones are auxins, gibberellins, cytokinins (growth promoters), abscisic acid (growth inhibitor), and ethylene (both promotion and inhibition).

Auxins

They are weakly acidic organic substances having unsaturated ring structures that promote cell enlargement of shoots in the concentration range of 10-100 ppm, which is inhibitory to the growth of roots.

• Natural auxin is indole 3-acetic acid or IAA. Some other examples are IBA, NAA, 2,4-D, 2,4,5-T. 1AA is synthesized inside shoot tips, young developing leaves, and seeds.

Auxins Functions

1. Cell Enlargement. Auxin promotes cell growth at a concentration of 10 ppm in the stem and 0.0001 ppm in the root.
2. Apical Dominance. Axillary buds do not sprout near the apical bud due to the secretion of auxin by it.
3. Prevention of Abscission. Auxin prevents the premature falling of leaves and fruits.
4. Movements. Phototropic, geotropic, and other plant movements are caused by differential distribution of auxin.
5. Root Formation. Root formation on stem cuttings is stimulated by auxins like NAA and IBA.
6. Tissue Culture. Auxin promotes callus formation in tissue culture. Along with cytokinin, it promotes the differentiation of callus into plantlets.
7. Fruit Growth. Auxin promotes fruit growth, sweetening of fruit, and even parthenocarpic development of fruit.
8.  Weedicides. In higher concentrations 2,4-D and 2,4,5-T are used as weedicides.

Gibberellins

They are mildly acidic tetracyclic organic substances that bring about cell elongation of leaves, stems, and fruits in intact plants. They are formed by the young leaves of buds, root tips, and developing seeds.

Gibberellins Functions

1. Growth. Gibberellin promotes growth in leaves, stems, internodes, and fruits. They are used to increase the yield of fruits and sugar in sugarcane.
2. Overcoming Dormancy. Dormant buds and seeds sprout in the presence of gibberellins.
3. Flowering. They can replace cold and long-day requirements for flowering in some plants.
4. Parthenocarpy. Like auxin gibberellin can induce the formation of seedless fruits.
5. Overcoming Dwarfism. Genetically dwarf plants grow to normal size on the application of gibberellins.

Cytokinins

They are mildly alkaline aminopurine or adenine derivatives that promote cell division in plants, for example., zeatin (natural), and kinetin (synthetic). Cytokinins are synthesized in the root tip and endosperm of developing seeds.

Cytokinins Functions

1. Cell Division, Differentiation and Morphogenesis. Cytokinins are essential for cell division, cell differentiation, and morphogenesis.
2. Prevention of Senescence. Aging of leaves, marketed vegetables, fruits, and cut flowers can be prevented by the application of cytokinin.
3. Accumulation of Nutrients. Cytokinins improve the yield and quality of fruits by stimulating nutrient flow into them.
4. Resistance. They enhance the resistance of plants to environmental stresses and diseases.
5. Apical Dominance. Application of cytokinins overcomes apical dominance. The nearby axillary buds sprout.

Abscisic Acid (ABA)

It is a mildly acidic organic substance that functions as a general growth inhibitor.

• Abscisic acid can counter the growth-promoting activity of auxins, gibberellins, and cytokinins.
• It helps the plant to overcome stress conditions mostly through induction of dormancy. Therefore, it is known as a stress hormone as well as dormant.

Abscisic Acid Functions

1. Controlled Growth. By counteracting the effect of other hormones, abscisic acid or ABA controls growth.
2. Wilting. Under conditions of stress, it causes wilting and senescence of leaves.
3. Abscission. It promotes the abscission of flowers and fruits.
4. Dormancy. Abscisic acid causes dormancy of buds and seeds.
5. Transpiration. It checks transpiration by causing the closure of the stomata. Because of this, abscisic acid can also be used as an antitranspirant.

UP Board Class 10 Biology Notes For Coordination In Plants Long Answer Type Questions

Question 1.

1. Mention the role of
   1. Auxin
   2. Abscisic acid.
2. How do plants respond to external stimuli?

Answer:

1. Auxin. It promotes cell growth, and apical dominance, and prevents premature leaf and fruit fall while differential distribution causes tropic movements.
   1. Abscisic Acid. It moderates growth promotion by auxin and gibberellins, prepares the plant for stress tolerance, and induces dormancy of buds and seeds.
2. Plant Response to External Stimuli. Plants respond to external stimuli by the two types of movements- turgor movements and growth moments.

Turgor Movements. They are caused by changes in the size and shape of cells through loss and gain of water, for example., opening and closing of stomata, haptonasty in Mimosa pudica, and hydronasty in many grasses.

Growth Movements. They are movements caused by unequal growth. Growth movements can be nondirectional or directional. The non-directional movements are called nastic movements.

• They are not related to the direction of stimulus but to the structure of the responding organ, for example., the opening and closing of flowers.
• The directional movements are called tropic movements. They mostly occur in cylindrical organs. The direction of this growth movement is related to the direction of stimulus, for example., phototropism.

UP Board Class 10 Biology Our Environment Question And Answers

Question 1. Why are some substances biodegradable and some non-biodegradable?
Answer: There are two types of substances, biological origin and man-made. Biological origin waste articles can be degraded by decomposer organisms because they have enzymes to do so, for example, garbage, livestock waste, agricultural waste, paper, etc.

They are called biodegradable substances. Most man-made articles cannot be degraded by decomposers because they do not have enzymes to do so, for Example plastic, glass, crockery, and metallic cans. Such articles are called non-biodegradable substances.

Question 2. Give any two ways in which biodegradable substances would affect the environment.
Answer:

1. Foul Smell. Biodegradable substances begin to stink after a few hours. They emit a foul smell.
2. Pathogens and Pests. Pathogens and pests multiply rapidly in the heap. They spread diseases through flies, mosquitoes, cockroaches, and rats.

our environment class 10 question answer

Question 3. Give any two ways in which non-biodegradable substances would affect the environment.
Answer:

Dumping Area. It becomes a source of pollution to groundwater and the emission of foul gases. There is a limit to the creation of new dumping areas as it makes the land barren and an eye sore.

Biological Magnification. Soluble persistent pesticides like DDT, and heavy metals (For example lead, cadmium, nickel, mercury) enter the food chain through soil, groundwater, and plants. They change and increase in concentration at higher trophic levels. Several diseases are caused by them.

UP Board Class 10 Biology Our Environment Question And Answers Paragraph-Based Question

The human body is made up of five important components of which water is the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields.

These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants.

As these chemicals are not biodegradable, they accumulate progressively at each trophic level. The maximum concentration ofthese chemicals gets accumulates in our bodies and greatly affects the health of our mind and body.

Question 1. Why is the maximum concentration of pesticides found in human beings?
Answer: Human beings belong to lie lot of food chain

Question 2. Give one method that could be applied to reduce our intake of pesticides through food to some extent.
Answer: Organic farming of Biopesticides/through the washing of vegetables, fruit; and grains

Question 3. Various steps in a food chain represent

1. Food Web
2. Trophic Level
3. Ecosystem
4. Biomagnification

Answer: 2. Trophic Level

Question 4. About various food chains operating in an ecosystem, man is a

1. Consumer
2. Producer
3. Producer And Consumer
4. Producer And Decomposer

Answer: 1. Consumer

class 10 chapter 15 science notes

UP Board Class 10 Biology Our Environment Short Answer Type Questions

Question 1. Mention the basis of classifying substances as biodegradable and non-biodegradable. Give two examples
Answer: Putersxibility or the (lie ability to get decomposed or not. Biodegradable substances are decomposed by saprophytes, for example; food leftovers used leaves leaves.

Non-biodegradable substances are not decomposed by saprophytes as they do not have enzymes for them, for example, milk pouches, and aluminum foil.

Question 2. If nil the wastes we generate are biodegradable, what effect will this have on the environment? Write two virtues that will be imbibed if the people are made to understand that the generation of waste should be restricted to biodegradable only.
Answer: There will be no pilling up of waste, nor there will be pressure to acquire Jand for their disposal.

Biodegradable waste gets decomposed by saprophytes within 2 to 3 months producing manure, compost, biogas, etc. There will be recycling of nutrients. Decomposers release nutrients from biodegradable wastes.

class 10th science chapter 15 question answer

The same arc is picked up by plants for their nutrition and growth. Virtues. Many diseases will disappear, and Earth will remain clean. Manure and compost will be available for crops, Biogas shall be available for energy and lighting. CM.

Question 3. Write two harmful effects of using plastic bags on the environment. Suggest alternatives to the usage of plastic bags. List any two practices that can be followed to dispose of the waste produced in our homes.
Answer: Harmful Effects, Plastic is non-biodegradable. Therefore, waste plastic bags cause pollution of land and water bodies, Waste plastic bags thrown indiscriminately block the drainage system, and They harm or even kill stray animals, Burning of waste plastic releases toxic gases. Alternatives. Use of jute or cloth bags, paper bags (if) Use of washable or biodegradable containers.

Separation of recyclable articles for rag pickers. Separation of biodegradable and non-biodegradable wastes in separate bins. Use of container bottles for storing articles in kitchens Composting of kitchen wastes for the kitchen garden.

chapter 15 class 10 science notes

UP Board Class 10 Biology Our Environment Question And Answers Long Answer Type Questions

Question 1. Distinguish between biodegradable and nonbiodegradable substances. List two effects of each of them in our environment
Answer:

• Foul Smell. Biodegradable substances begin to stink after a few hours. They emit a foul smell.
• Pathogens and Pests. Pathogens and pests multiply rapidly in the heap. They spread diseases through flies, mosquitoes, cockroaches, and rats.
• Dumping Area. It becomes a source of pollution to groundwater and the emission of foul gases. There is a limit to the creation of new dumping areas as it makes the land barren and an eye sore.
• Biological Magnification. Soluble persistent pesticides like DDT, and heavy metals (For example lead, cadmium, nickel, mercury) enter the food chain through soil, groundwater, and plants. They change and increase in concentration at higher trophic levels. Several diseases are caused by them.

UP Board Class 10 Biology Notes For Heredity

Why do individuals produced after the sexual process, have similar designs?

• Heredity is the study of the transmission of genetic characteristics from parents to offspring and the laws governing such a transmission.
• Along with genetic characteristics, variations also appear during the transmission.
• The branch of biology that deals with the study of heredity and variations is called genetics. The term was coined by Bateson (1906).

heredity and evolution

UP Board Class 10 Biology Notes For Heredity Inherited Traits

Inherited traits are features that an organism receives from its parents through their genes, for example, free ear lobes, attached ear lobes, roller tongue, non-roller tongue, black hair, blonde hair, blue eyes, dimpled and non-dimpled cheeks, and thick and thin lips. The varied expression of so many trials is the reason for such a large number of variations in the same population.

Attached and Free Ear Lobes

Observe The Ear Lobes Of Your Classmates. Note That The Majority Of Them Have Free Ear Lobes. Classmates With Attached Ear Lobes Are Fewer In Number. Record The Ear Lobes Of The Parents Of Your Classmates. Again More Parents Have Free Ear Lobes.

If Both Parents Have Attached Ear Lobes, Their Child Will Also Have Attached Ear Lobes. In Other Cases, Inheritance Depends Upon The Genetic Nature Of The Parents And The Dominance Of Free Ear Lobes Over The Traits Of Attached Ear Lobes.

UP Board Class 10 Biology Notes For Heredity Rules For The Inheritance Of Traits—Mendel’s Contributions A

What will be the trait seen in a child, when both the father and mother contribute an equal amount of genetic material (DNA)?

As found out in the inheritance of the trait of ear lobes, both mother and father contribute an equal amount of genetic material to the child.

It means that the child receives two versions of the trait, one from each parent. The expression of the trait in the child depends upon the nature of the traits contributed by the parents. The rules of such inheritance were worked out by Mendel in the 19th century.

Mendel—The Father Of Genetics

Gregor Johann Mendel (1822-1884) found out the mechanism of the passage of traits from one generation to the next and so on. Because of this discovery, he is known as the father of genetics.

• Mendel was born to a farmer’s family in the village of Silesian (now part of the Czech Republic). After graduating he joined a monastery in Brunn (then Austria now Bruno of the Czech Republic) in 1843. He became a priest there in 1847.
• In 1851 Mendel went to Vienna to study science and mathematics. He returned as a substitute teacher as he failed to clear the certificate course for teaching.
• In 1856, Mendel became interested in hybridization experiments on Garden Pea (Pisum sativum) which had several contrasting traits.
• He first raised pure breeding plants and then selected seven characters that had two alternate traits for breeding.
• He read out the results of his experiments in two sittings of Natural History of Brunn in 1865. The same was published as “Experiments on Plant Hybridization” in the proceeding of the society in 1866.

However, Mendel’s work remained unnoticed till similar results were obtained by three scientists independently in 1900—de Vries of Holland, Carl Correns of Germany, and Tschermak Seysenegg of Austria. Mendel’s original paper was found out and republished in Florida in 1901.

heredity notes

Mendel’s Experimental Material

Mendel selected Pea Plant (Pisum sativum) as experimental material because :

• It occupies a small space.
• It has a short life span and annual nature.
• Presence of easily detectable contrasting traits.
• Formation of a large number of seeds.
• It has a flower structure that enables cross-pollination but is normally self-pollinated.
• The plant requires little aftercare.

Seven Characters with Contrasting Limits Selected by Mendel

Mendel’S Experiments

Mendel made reciprocal crosses between plants having alternate traits like tall and dwarf, round seeded and wrinkled seeded.

He emasculated (removed anthers) of 50% of the plants of each type and used them as female parents. Pollen for other traits was collected and dusted over their stigmas. Flowers were kept covered with paper and thus obtained were hybrid and constitute tblS CF0SS Were collected and sown next year.

The plants thus obtained were hybrid and F₁ or first filial generation. The hybrids were not intermediate between the traits but belonged to one of them. The expressed trait is called dominant while the other unexpressed one is called recessive.

Mendel allowed the F₁ plants to self-breed. He obtained F₂ generation which had both types of plants, dominant 75% and recessive 25%. Mendel further self-bred F₂ plants and obtained F₃ generation.

The recessive trait individuals produced recessive trait offspring. One-third of the dominant trait plants formed only dominant offspring while 2/3 behaved like the hybrids giving rise to both dominant and recessive trait offspring in the ratio of 3: 1.

Such a ratio comes to 1 pure dominant, 2 hybrid dominant, and 1 pure recessive. It is called the genotypic ratio.

Monohybrid Cross: Mendel studied the inheritance of two traits of a character at one time through cross-breeding and then self-breeding. It is called a monohybrid cross.

In a cross between pure tall and pure dwarf Pea plants, Mendel obtained only tall plants in the F₁ generation. On self-pollination of F₁ plants, the F₂ generation had both tall and dwarf plants in the ratio of 3: 1.

It is called the monohybrid ratio. The occurrence of dwarf plants in the F₂ generation is possible only if the trait of dwarfness is present in the F₁ generation but remains unexpressed due to its recessiveness.

Mendel, therefore, proposed that each individual carried two factors for a character. They separate randomly at the time of gamete formation and come together randomly at the time of fertilization.

10th heredity and evolution class 10 notes

Work out the Dominant and Recessive Trait 

It is a cross between purple-flowered plants with white-flowered plants. The hybrid or F₁ plant is purple-flowered though it has received the factor for white flowers as well.

This is proved by the plants of F₂ generation where both purple and white flowered ratio of 3: 1. This dominant over the trait of white flower colour as plants occur in the also indicates that the trait for purple colour is the latter remains Ft” Self Fertilisation unexpressed in F1 generation.

Dihybrid Cross: It is a cross between two individuals for studying the inheritance of traits of two different characters. Mendel crossed a pure breeding round green-seeded (RRyy) plant with the pure breeding wrinkled yellow-seeded plant (RR).

F₁ plants or hybrids were all round and yellow-seeded (RrYy). On self-breeding the F₁ plants Mendel obtained four types of plants—round yellow (315/556 or 9/16), round green (108/556 or 3/16), wrinkled yellow (101/556 or 3/16) and wrinkled green (32/556 or 1/16).

Here, round yellow and wrinkled green are new combinations of traits. This is possible only if there is an independent assortment of traits of the two characters. The ratio is called the dihybrid ratio.

Important Terms :

Character: It is a distinct feature of an organism like the flower colour, or height of a plant.

Trait: It is the alternate expression of a character, for example, tallness for height.

Gene: It is a linear segment of DNA or chromosome that functions as a unit of inheritance.

Alleles: Genes occurring in homologous chromosomes at the same locus are called alleles or allelomorphic pairs.

Being particulate they are also called factors or units ofinheritance. They may express the same trait or different traits of character, for example, TT, Tt, tt, RR, Rr, rr. Here, the capital letter represents the dominant factor (T for tallness) while the small letter signifies the recessive factor (t for dwartness).

class 10 chapter heredity and evolution notes

Homozygous:  It is an organism with identical alleles, for Example, TT, RR, r r, 1 1. Homozygous individuals are generally genetically purebred.

Heterozygous: It is an organism which possesses contrasting (both dominant and recessive) traits of character, Example Tt, Rr.

Dominant Factor: It is an allele or factor that expresses its effect in both homozygous and heterozygous states, Example TT, Tt.

Recessive Factor: It is an allele or factor that is unable to express its effect in the heterozygous state. Recessive factor expresses its effect only in the homozygous state, Example tt.

Differences Between Dominant And Recessive Factors

F1 Generation (First Filial Generation). It is a generation of hybrids that are formed from a cross between two genetically different pure-breeding individuals.

F2 Generation (Second Filial Generation). It is a generation that is formed through inbreeding amongst members of the Fj generation.

True Breeding (Pure Line): It is a lineage of homozygous or genetically pure individuals that produce similar genetically pure offspring.

heredity in science

Monohybrid Ratio: The ratio of types of individuals produced in the F2 generation, when the inheritance of a single character is studied, is called the monohybrid ratio. The phenotypic ratio is 3: 1 while the genotypic ratio is 1 : 2: 1.

Dihybrid Ratio: The ratio of types of individuals produced in F2 generation when the inheritance of two characters is studied is called the dihybrid ratio. Its phenotypic ratio is 9: 3 : 3: 1 while the genotypic ratio is 1: 2: 2: 4: 1: 2: 1: 2: 1.

Phenotype: It is the morphologically expressed character of an individual, for Example round seeded, wrinkled seeded. the  In case of a recessive trait, the phenotype and genotype are the same. In the case of a dominant trait, the phenotype is genetically of two types, pure (Homozygous) and hybrid (Heterozygous).

Genotype: It is the genetic complement of an individual about one or more characters whether or not their factors find expression in the phenotype. example the le, genotype of tall pea plants can be TT or Tt. In Tt, the factors for tallness (T) find expression while the factor for dwarfhess remains (t) unexpressed.

Differences Between Phenotype And Genotype

Mentalism

(Mendel’s Laws of Inheritance)

Principles or laws of inheritance as discovered by Mendel (1866) are collectively called Mendelism. They are three in number —the law of dominance, the law of segregation and the law of independent assortment.

Law of Dominance: Out of the two alleles or factors in hybrid, | Parents| only one expresses its effect. The other allele remains unexpressed. The allele which finds expression in the hybrid is called the dominant allele or factor while the unexpressed allele is known as the recessive allele or factor.

• The dominant allele is designated by a capital (Example T) letter while the recessive allele is designated by a small letter (t) of the alphabet.
• Cross a pure tall (TT) plant of Pea with a pure dwarf (tt) plant. Fj plants are all tall though they have also received an allele for dwarfness.
• This shows that the factor or allele of tallness is dominant over the allele of dwarfness.

genetics and evolution

Law of Segregation: The two alleles or factors of a character particulate entities which remain distinct in an individual whether or not any of them expresses its effect. Both the factors separate or segregate at the time of gamete formation. A gamete receives only one of the two factors for the character. It is, therefore, always pure. The law of segregation is, therefore, also known as the law of purity of gametes. The double nature of factors is restored after fertilization.

Select pure tall (TT) and pure dwarf (tt) Peas plants as parents. Cross the two. The hybrid or plants of the F₁ generation are all tall despite their having received a factor for dwarfness as well.

F₁ plants are allowed to self-breed and produce F₂ generation. In the F₂ generation, both tall and dwarf plants appear in the ratio of 3: 1. It is possible only if the factor for dwarfness was present in the F₁ generation. It separates from the factor of tallness during the formation of gametes. On fusion of two gametes each carrying the factor for dwarfness will produce an offspring with the recessive character of dwarfness.

Law of Independent Assortment: The two factors or alleles of a character separate independent of factors of another character at the time of gametogenesis. They also come together independently of one another during fertilization. As a result of independent assortment, fertilization produces a new combination of traits or factors. They are called recombinations.

Select pure-breeding tall round-seeded and pure-breeding dwarf wrinkled-seeded Pea plants as parents. Cross the two. Plants of the F₁ generation or hybrids are all tall and round-seeded because of the dominant nature of alleles of tallness and round-seededness. Raise F₂ generation by allowing the F₁ plants to self-breed.

genetics heredity

F₂ generation has four types of plants-tall and round seeded (9/16), tall and wrinkled seeded, (3/16), dwarf and round seeded (3/16) and dwarf and wrinkled seeded (1/16). Only two of these (tall rounded and dwarf wrinkled) are parental types. The other two types (tall wrinkled and dwarf rounded) are new combinations. New combinations can appear only if the factors for the two characters separate and come together independently of one another.

Contribution By The Parents

Each parent has two sets of genes or chromosomes. A gamete receives only one set of genes or chromosomes. When the gametes fuse during fertilization, the double set or diploid number of genes or chromosomes is restored.

Therefore, in sexual reproduction, each parent contributes half of the genetic material. Thus, both parents contribute equally. Of course, there is reshuffling of chromosomes during gametogenesis and fertilization that results in variations and independent assortment.

In asexual reproduction, there is no halving of genetic material, nor doubling of halved material. Instead, the full gene complement or genetic material of the parent is transferred to the daughters through mitotic divisions.

UP Board Class 10 Biology Notes For Heredity How Do The Traits Get Expressed

How does the mechanism of cellular DNA (gene) work in the production of hormone enzymes?

Traits are morphological or physiological expressions of factors or genes. Genes are segments of DNA. They operate through the formation of wRNA which then forms structural or enzymatic proteins. A dominant factor produces a fully functional protein.

• A recessive factor does not form a fully functional protein. Therefore, while a dominant factor can express its effect even in the heterozygous state, a recessive factor cannot do so. It shows its effect only when it is present in the homozygous state.
• The character of height in Pea is controlled by growth hormones. They are synthesized through enzymes produced by proteins formed by growth factors. The dominant factor for tallness (T) synthesises a protein that efficiently gives rise to growth hormones.
• Therefore, the plant becomes tall. In the case of the recessive factor for dwarfness (t) less efficient protein is formed when it is present in the homozygous state. As a result growth hormones are formed and the plant remains dwarfed.

UP Board Class 10 Biology Notes For Heredity Sex Determination

How is the sex of a newborn individual determined? Does it depend on the inheritance of X and Y chromosomes?

Sex determination is the establishment of maleness and femaleness of the individuals through the formation of their sex organs. In some animals, sex is determined environmentally while in the majority of animals and humans, it is controlled genetically.

In turtle Chrysema picta, females are formed if the eggs are incubated at a temperature of about 33°C. A temperature below 28°C forms male animals.

In the lizard Agama agama, males are formed at higher temperatures.

Annelid Ophryotrocha changes sex from male to female as it grows old. Similar sex changes also occur in some snails.

Sex Determination in Humans: Genetic control of sex determination is carried out by chromosomes. There are two types of chromosomes, autosomes and allosomes.

Autosomes control various functions of the body other than sex. Allosomes (=heterosomes) determine sex along with other functions. They are called sex chromosomes.

Human beings possess 23 pairs of chromosomes. 22 pairs are autosomes. One pair of chromosomes are sex chromosomes or allosomes. The two allosomes are similar in females.

They are XX chromosomes. The two allosomes of males are different. One is X-chromosome while the other is smaller and called Y-chromosome.

Human Females are 44 + XX while human males are 44 + XY. Because of the similar nature of X-chromosomes the sex chromosomes of females are called homomorphic. They are heteromorphic m males. The Emma endosperm forms one type of egg, 22 + X.

The males are heterogametic. They form two types of sperm, (22 + Y) and gymnosperms (22 + X). The two types of sperms are produced in equal numbers.

1 n + x and 22 + Y chance factor which depends upon whether an angiosperm fuse with the egg and forms male is 50: 50 or 44 + XY) or a gymnosperm fuse with the egg to produce a female baby (22 + X and 22 + X or 44 )ÿ chance of the birth of a boy or girl.

UP Board Class 10 Biology Notes For Heredity Questions And Answers

Question 1. How do Mendel’s experiments show that traits may be dominant or recessive?
Answer:

Mendel’s crosses between plants having visible contrasting traits proved that traits may be dominant or recessive. He crossed a pure tall Pea plant with a pure dwarf Pea plant.

• All the plants of the F₁ generation were tall and none J with medium height or dwarfnature.
• On self-breeding of F₁ plants, Mendel obtained two types of plants, tall: and dwarf in the ratio of 3: 1. It means that the factor of dwarfness was present in Fj plants.
• It did not express its effect because it is recessive while the factor for tallness is dominant as it can express its effect and suppress that of the factor for dwarfness.

Question 2. How do Mendel’s experiments show that traits are inherited independently?
Answer:

The traits of different characters are not linked. The traits of one character are inherited independently of the traits of, another character. Mendel performed a dihybrid cross between rounded green-seeded plants (RRyy) and wrinkled yellow-seeded plants (rrYY).

• In the F1 generation, he obtained round yellow-seeded plants. On self-breeding F₁ plants, Mendel obtained a progeny of F₂ generation of four types of plants—round yellow seeded (9/16), round green seeded (3/16), wrinkled yellow seeded (3/16) and wrinkled green seeded (1/16).
• In this progeny, there are two parental types and two new combinations or recombinations. Recombination of traits can occur only if they are inherited independently of one another.

Question 3. A man with blood group A marries a woman with blood group 0 and their daughter has blood group O. Is this information enough to tell you which of the traits, blood group A or O, is dominant? Why or why not?
Answer:

No, The appearance of a recessive trait can occur only when its factors are in the homozygous state. The appearance of a dominant trait can occur both in homozygous and heterozygous states.

• In this particular cross, both A and 0 blood groups can be dominant as well as recessive. Possibility 1. Blood group A is dominant. Father with blood group A can be I AIA or IA 1°. The mother with blood group 0 must be I°I°.
• The daughter can be genetically IAI° or I°I°, that is of blood group A or 0. Possibility 2. Blood group 0 is dominant. Mothers with blood group 0 can be I°I° or 1° IA. Father with blood A should be I I only. The daughter would be of blood group 0 or A.

Question 4. How is the sex of the child determined in human beings?
Answer:

The sex of the child is determined by the chromosome complement of the gametes that fuse during fertilization. In human beings, females are homogametic. They produce only one type of ova, i.e., 22 + X.

• Males are heterogametic. They produce two types of sperm, angiosperms with 22 + Y chromosome complement and gymnosperms with 22 + X chromosome complement Sex of the child will depend upon the type of sperm that fuses with the ovum.
• It will be male if fusion has occurred with endosperm (44 + XY) and female if fusion has occurred with a gymnosperm (44 + XX).

Class 10 Biology Life Process Notes For Excretion

What is excretion? What are the excretory products?

• Excretion is the removal of metabolic wastes from the body.
• Metabolic wastes are not only unwanted by-products but are often toxic, For Example, urea, uric acid, ammonia, creatinine, excess salts, drugs, vitamins, etc.
• The excretory system is a system of organs and tissues that take part in the separation, collection, and elimination of waste products.
• Elimination of waste products maintains a favorable internal environment in the body. Different organisms have different mechanisms to eliminate their waste products.
• Excretion in Unicellular Organisms An excretory system is absent, However, waste products are regularly produced during their metabolism, For Example., ammonia, and carbon dioxide. They pass out into the surrounding water through diffusion, (For Example., Amoeba) from the surface of the body.
• Excretion in Multicellular Organisms In sponges and coelenterates excretion occurs through diffusion into the surrounding aquatic medium.
• Excretory structures developed in Platyhelminthes (flame cells), annelids (nephridia), crustaceans (green glands), insects (Malpighian tubules), mollusks (kidneys), and chordates (kidneys).
• Excretion or elimination of metabolic waste is accomplished through the urinary or excretory system. In humans, the excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.

life processes notes

Micturition

What Is The Need For Micturition?

The urge for micturition or voiding of urine begins to appear when the urinary bladder is nearly half-filled. However, one can overcome this urge till the urinary bladder is nearly full.

At this time the stretched urinary bladder sends a reflex for contraction. However, voluntary micturition can be undertaken at any time. The total urine produced per day under normal conditions is 1.6 – 1.8 liters.

Urine. It is a transparent fluid of amber color. Urine is 96% water, 2.5% organic substances (urea, uric acid, creatine, creatinine, oxalates, vitamins, hormones), and 1.5% inorganic solutes (sodium, chloride, sulfate, magnesium, calcium, phosphate).

” life processes”

Functions Of The Urinary System

1. Elimination of Metabolic Wastes. The urinary system eliminates both nitrogenous and non-nitrogenous metabolic wastes from the body.
2. Extra Materials. Kidneys flush out extra salts, pigments, drugs, and toxic substances from the body.
3.  Water Balance. It regulates the blood volume of the body through the control of fluid loss in urine.
4. Regulation of Blood Pressure. Kidneys secrete hormones (renin, erythropoietin) for regulating blood pressure in the body.
5. Other Functions. The urinary system regulates the salt balance of the body and the pH of the body fluids.

” notes for biology class 10″

Haemodialysis (Artificial Kidney)

What is Haemodialysis? Where is it needed?

• Kidney functioning may be impaired due to injury, infection, or reduced blood supply. This leads to the accumulation of urea and other waste products. Uremia can lead to death.
• In such a situation accumulated waste products are eliminated from the body by means of artificial kidneys. It works on the principle of dialysis and is called hemodialysis.
• An artificial kidney or dialysis machine consists of a number of semipermeable cellophane tubes immersed in a tank of dialyzing fluid. The dialyzing fluid has the same osmotic concentration as that of blood but is without nitrogen waste products, sulfate, and phosphate. Instead, it has more glucose.
• Blood from an artery (even vein also) is pumped out, mixed with heparin, and cooled to 0°C and then passed into cellophane tubes of the artificial kidney. Nitrogen wastes, sulfate, phosphate, and other wastes pass into dialyzing fluid.
• On purification, at the end of cellophane tubes, blood is taken to a warming machine, mixed with anti-heparin, and passed back into a vein. Hemodialysis is completed in 3-4 hours.
• After dialysis, a patient can resume normal working. However, if the kidney damage is severe, dialysis has to be repeated at intervals till a compatible kidney donor is found and a normal kidney is transplanted.

Organ Donation

1. It is the process of giving an organ or tissue by a person (organ donor) to a person (organ recipient) through surgical removal from the donor and transplantation of the same in the recipient. Organ donation is of two types, living donation and deceased donation.
2. In living donation, one of the two similar organs (For Example., kidney), a piece of organ (For Example., liver, lung, bone marrow) is given by a donor for restoring body function. In deceased donation, the organs of a dead person are taken out for transplantation.
3. For this, the person must have pledged to donate the organs or the family members agree to the same. A dead person can help ten persons to lead a normal life. Some common forms of deceased donation are heart, cornea, lung, liver, pancreas, intestine, trachea, skin, heart valves, and blood vessels.
4. Organ donation is a noble gesture and the public should be made aware of it so that more and more persons with life-threatening debility can come out of it.

notes 10

Class 10 Biology Life Process Notes For Excretion In Plants

Plants produce waste products like other organisms. However, they have different mechanisms for their disposal. Carbon dioxide is produced as waste during the night, oxygen is produced as waste during the daytime and excess water absorbed from soil is passed out into the atmosphere through diffusion. Roofs, also produce exudates having different types of wastes.

The main wastes of plants are secondary metabolites like alkaloids, organic acids, (For Example., oxalic acid), tannins (by-products of aromatic compounds), latex, gums (degradation products of cell walls), resins (oxidation products of aromatic compounds) and some inorganic salts.

These wastes are disposed of as follows :

1. Old Leaves. Waste products collect in old leaves which fall off.
2. Bark. Tannins, gums, and resins collect in the bark which is periodically peeled off.
3.  Old Xylem. Most waste products are collected in old nonfunctional xylems like heartwood.
4. Central Vacuole. Excess salts and waste products get stored in the central vacuole of the cells. They are not able to harm the living cytoplasm due to the presence of tonoplast over the vacuole.
5. Idioblasts. They are isolated plant cells that are specialized to store excretory materials, pigments, minerals, tannins, resin, gum, oil, latex, etc.
6. Root Exudates.

biology chapter 6 class 10 notes

Class 10 Biology Life Process Notes For Excretion Question And Answers

Question 1. Describe the structure and function of the nephron.
Answer:

• The nephron is the structural and functional unit of the kidney. A nephron is about 3 cm long and 20-60 cm in diameter. It has two components, renal capsule and renal tubule. The renal or Malpighian capsule has two parts, Bowman’s capsule and glomerulus.
• Bowman’s capsule is a blind broad cup-shaped end of a nephron. It encloses a bunch of capillaries called glomerulus. The glomerulus develops from a slightly broader afferent arteriole and passes into a slightly narrow efferent arteriole.
• The renal tubule has three parts proximal convoluted tubule (PCT), loop of Henle, and distal convoluted tubule (DCT). It is surrounded by peritubular capillaries formed by the efferent arteriole.

Function. Nephron takes part in urine formation. It has four components ultrafiltration, reabsorption, tubular secretion, and concentration.

1. Ultrafiltration. In the glomerulus, blood is under pressure due to the narrowness of the efferent arteriole. All small-sized solutes and a good part of water pass into Bowman’s capsule and then the proximal convoluted tubule as primary urine.
2. Reabsorption. The peritubular capillaries around PCT reabsorb useful substances present in the primary urine including some 75% of water.
3. Tubular Secretion. Peritubular capillaries actively secrete waste products remaining in their blood into the distal convoluted tubule. Waste-free blood passes into venules formed from the peritubular capillaries,
4. Concentration. Some 10% of water is passed out of the filtrate in the region of the loop of Henle by exosmosis. The remaining concentration occurs in collecting tubules under the effect of antidiuretic hormone or ADH (= Vasopressin).

class 10 transportation notes

Question 2. What are the methods used by plants to get rid of excretory products?
Answer:

1.  Carbon dioxide during the night, oxygen, and excess water during the daytime are got rid of through diffusion.
2. Roots get rid of many waste materials in the soil as exudate from their surface.
3. Deposition in the bark which is periodically peeled off.
4. Deposition in old leaves which fall off.
5. Deposition in old xylem which becomes functionless in conduction of sap.
6. Deposition in idioblasts and inside central vacuoles of cells.

• The amount of urine production is regulated by two phenomena—amount of blood and ADH or vasopressin. If there is an excess intake of water, the volume of blood will increase. It increases glomerular pressure and hence formation of more primary urine.
• Some water is absorbed from it in PCT and the loop of Henle. However, there is no secretion of antidiuretic hormone (= vasopressin) so dilute urine is passed out from the kidneys. Its amount is higher than the normal.
• When the body is deficient in water (as during summer due to sweating) there will be a lesser amount of blood being filtered and hence lesser amount of primary urine.
• ADH or vasopressin is secreted by the pituitary. It helps in withdrawing water from the urine. This produces a smaller and more concentrated amount of urine.

Class 10 Biology Life Process Notes For Excretion Multiple Choice Questions

Question. In the excretory system of human beings, some substances in the initial filtrate such as glucose, amino acids, salts, and water are selectively reabsorbed in

1. Urethra
2. Nephron
3. Ureter
4. Urinary bladder.

Answer: 2. Nephron

process notes

Class 10 Biology Life Process Notes For Excretion Short Answer Type Questions

Question 1. What is excretion? How do unicellular organism remove their wastes?
Answer:

Excretion is the elimination of metabolic wastes, toxins, and excess salts from the body. In unicellular organisms, excretion is carried out through diffusion from the surface.

Question 2. A major amount of water is selectively reabsorbed in the tubular part of the nephron. What are the factors on which the amount of water reabsorbed depends?
Answer:

• Amount of excess water present in the filtrate.
• Amount of waste to be eliminated
• Length of the loop of Henle.

Question 3. 1. Name any two substances that are selectively reabsorbed as the urine flows along the tube,

2. Name the part of the excretory system In which mine is stored for some time.
Answer:

1. Glucose, amino adds.
2. Urinary bladder,

important notes

Question 4. “About 180 liters of renal filtrate is produced each day blit only 1.5 liters of urine Is excreted out”. Justify the statement.
Answer:

The renal filtrate contains all the small size/volume solutes and most of the water from the blood. Therefore, the volume of renal filtrate is higher. Most of the useful solutes and over 75% of water are reabsorbed by blood capillaries from the renal filtrate.

As a result, the volume of the filtrate decreases. Further, loss of water occurs in the loop of Henle and collecting tubules. Therefore, the final urine formed is quite small as compared to the original glomerular filtrate.

Question 5. Define excretion. Write any two vital functions of the kidney.
Answer:

Excretion. It is the removal of metabolic wastes, toxins, and excess salt from the body.

Vital Functions of Kidney. (1) Separation and elimination of metabolic waste products. (2) Maintenance of blood pressure and water balance of the body.

class 10 science notes biology

Question 6. 1. Name one nitrogenous waste present in urine.

 2. What is the basic unit of the kidney called?

3. How the amount of urine produced is regulated?
Answer:

1. Nitrogenous Waste. Urea (most common).
2. Basic Unit of Kidney. Nephron.
3.  Regulation of Amount of Urine. It is carried out by antidiuretic hormone (ADH) or vasopressin. It is secreted in good amounts if water is to be conserved.

• • Then only concentrated urine is passed out. If the amount of water is in excess, very little ADH is produced and dilute urine is allowed to pass out.

Class 10 Biology Notes For Respiration

What Is Respiration? Define Respiratory Substrate.

Respiration is a multistep enzymatic breakdown of organic compounds like glucose that releases small packets of energy at various steps. Glucose that is commonly broken down in respiration is called respiratory substrate. In the aerobic type of respiration, oxygen is used as a terminal oxidant. Besides energy, carbon dioxide is released.

respiration definition

Class 10 Biology Notes For Respiration Experiment

Carbon Dioxide Is Released During Respiration

Take two test tubes. Half-fill them with freshly prepared lime water. Blow air into one test tube by means of a tube. Note the time taken by lime water to turn milky. Now, blow fresh air into the second test tube by means of a syringe (or Pichkari). Repeatedly do it till lime water turns milky. Note the time taken. Compare the two time periods.

Lime water turns milky only when it reacts with carbon dioxide. Air blown out of the mouth is the one which has come out from the lungs. As it turns lime water milky very soon, it is clear that respiration releases carbon dioxide. ‘Atmospheric air contains comparatively very low concentrations of carbon dioxide as it takes a long time to change lime water milky.

what is respiration class 10

Class 10 Biology Notes For Respiration Cellular Respiration

What Is Cellular Respiration?

Break-down of respiratory substances occurs only inside living cells. It is, therefore, called cellular respiration. Oxygen used in cellular respiration and carbon dioxide produced by it are called respirators or metabolic gases.

Complex animals have three more steps for respiration—breathing, external respirator’ exchange and internal respiratory exchange. There is a direct respiratory exchange of gases in simple animals and most plants.

Types of cellular respiration

Class 10 Biology Notes For Respiration Release Of Energy ATP

How Much Energy Is Released By Breakdown Of One Molecule Of Glucose?

Respiration releases energy in small steps. A part of this energy is dissipated as heat while another part is used in the formation of adenosine triphosphate (ATP).

About 50% of the released energy is used in the formation of ATP from ADP and inorganic phosphate (Pi or P)

ADP + Pi or (P) + Energy ↔ ATP or ADP ∼ (P)

About 30.5 kJ or 7.3 kcal of energy is used in the synthesis of one molecule of ATP from ADP and Pi. The same energy is released whenever energy is required for any activity of the cell. ATP functions as the energy currency of the cell.

The energy is used in various functions of the cell (just as a batter) and can be used to provide electricity for diverse activities) for example, muscle contraction, nerve conduction, membrane permeability, active absorption, cyclosis or cytoplasmic streaming, working of genetic system, biosynthesis, etc.

describe the process of respiration

Class 10 Biology Notes For Respiration Respiration And Photosynthesis

What Is The Difference Between Respiration And Photosynthesis?

Respiration is a breakdown or catabolic process which releases energy stored in chemical bonds of the respiratory substrate. Photosynthesis is a build-up or anabolic process which traps solar energy and uses the same in the formation of chemical bonds in organic compounds. The two processes are complementary as the products of one are used as raw materials for the other.

Photosynthesis occurs only during the daytime in green cells. Respiration occurs all the time in all the living cells. However, the rate of photosynthesis is several times the rate of respiration, so a lot of food gets stored in plants after meeting their respiratory requirement.

Differences Between Respiration And Photosynthesis

Class 10 Biology Notes For Respiration Types Of Respiration

Respiration is of two types: anaerobic and anaerobic.

Aerobic Respiration. It is a mode of respiration in which the respiratory substrate is completely oxidised to form carbon dioxide and water. It is the common mode of respiration since it yields the maximum energy contained in the respiratory substrate.

characteristics of respiration

A part of the liberated energy is stored in some 38 ATP molecules. The rest is dissipated.

Aerobic respiration occurs in two steps, cytoplasmic and mitochondrial.

1. In cytoplasm glucose is broken into two molecules of 3-carbon compound pyruvic acid. Two ATP and two NADH₂ are also formed. This cytoplasmic step is called glycolysis.

2. In mitochondria one pyruvic acid undergoes decarboxylation and dehydrogenation to form 4NADH₂, one FADH₂; one ATP and 3 molecules of carbon dioxide.

The mitochondrial step is called the Krebs cycle after the scientist who discovered it in 1940. Both NADH₂ and FADH₂, are used in mitochondria to form ATP molecules through a process called oxidative phosphorylation. One NADH-, produces 3 ATP molecules while one FADH₂ forms two ATP molecules.

Total NADH₂ formed in aerobic respiration = Glycolysis – 2NADH₂

Kreb’s cycle — 4 NADH₂ x 2 = 8NADH₂

Total FADH₂ formed in aerobic respiration = 1 FADH₂ x 2 = 2FADH₂

Direct ATP formed = Glycolysis – 2ATP = Kreb’s cycle – 1 ATP x 2 = 2ATP

From 10 NADH₂, 10 x 3 = 30, From FADH₂ 2 x 2 = 4, Direct ATP = Glycolysis — 2, Krebs’ cycle — 2.

Total 30 + 4 + 4 = 38 ATP

Class 10 Biology Notes For Respiration Anaerobic Respiration

What Is Anaerobic Respiration? Why It Is Uncommon?

It is a breakdown of the respiratory substrate without using oxygen. A complete breakdown into inorganic products is absent At least one product of anaerobic respiration is an organic substance. Anaerobic respiration occurs in the cytoplasm only. It has two components, glycolysis and reduction of pyruvic acid produced in glycolysis.

Anaerobic respiration occurs in many bacteria, yeast and some other microorganisms. In yeast, the most common products are ethyl alcohol (C₂H₅OH) and carbon dioxide. Anaerobic respiration also occurs in striated muscles during heavy exercise. Here pyruvate is reduced to form lactic acid. Lactic acid causes pain in the muscles and forces the athlete to stop further exercise.

examples of respiration

Fermentation. It is an anaerobic breakdown of sugars by microorganisms that is usually accompanied by effervescence or bubbling out of waste gases and the formation of a variety of products like alcohol and organic acids.

The fermentation activity of yeast is used in the baking industry and brewing industries. The formation of yoghurt, curd, idli and dosa is also the fermentation activities of specific bacteria. Acids produced through fermentation include vinegar, citric acid, lactic acid and butyric acid.

Class 10 Biology Notes For Respiration Fermentation Experiment

In Fermentation, Yeast Produces Alcohol And Carbon Dioxide.

Take a test tube. Fill 5/6 of it with 10% glucose solution or some fresh fruit juice. Add half a spoonful of yeast to it. Pour a drop of non-drying oil over the surface of the solution to exclude oxygen. Fit a one-holed cork having a delivery tube into the mouth of the tube.

Dip the free end of the delivery tube in a tube having freshly prepared lime water. Note bubbles of gas coming out of the sugar solution. They pass into lime water. Lime water turns milky indicating that yeast is producing carbon dioxide. Remove the cork and smell the solution. It smells of alcohol. Yeast, therefore, produces alcohol and carbon dioxide during fermentation or anaerobic respiration.

physiology of respiration notes

Differences Between Anaerobic And Aerobic Respiration

Class 10 Biology Notes For Respiration Exchange Of Gases In Plants

Higher plants respire aerobically. The rate of respiration is different in different parts. Growing points of both stem and roots, cambial cells, floral buds, growing fruits and germinating seeds respire more actively than other parts.

Most parts respire slowly because being fixed, plants have a lower requirement of energy. Plants also do not have any transport system for gases. Instead, they have a well-connected network of intercellular spaces for the diffusion of gases. Even then every part of the plant has its own system of exchange of gases.

Leaves And Young Stems. They possess stomata for gaseous exchange. During day time carbon dioxide is consumed in photosynthesis and oxygen evolves. Stomata help in the inward diffusion of carbon dioxide and the outward diffusion of oxygen. The oxygen required for respiration is generated internally. Similarly, carbon dioxide produced in respiration is consumed in photosynthesis.

At night, plants also require oxygen for respiration. They may also release carbon dioxide. The exchange occurs through some partially opened stomata as well as gases stored in intercellular spaces during the daytime.

Older Stems And Roots. They possess permanently open pores called lenticels. A lenticel has a number of loosely arranged complementary cells. Their interspaces connect atmospheric air with air present in the intercellular spaces.

Young Roots. Epiblema cells and root hairs of young roots are permeable to metabolic gases. They are in contact with small spaces present in between soil particles. Oxygen from soil diffuses into roots while carbon dioxide comes out of the roots into air spaces. Soil air spaces are in contact with soil pores present on the surface of the soil.

However, in waterlogged soil, the soil aerating system disappears. In the absence of oxygen, young roots stop growth and fail to undertake active transport. Cell membranes lose permeability. As a result, the plant devoid of root aeration, withers and may die.

Class 10 Biology Notes For Respiration Multiple Choice Questions And Answers

Question 1. Anaerobic process

1. Takes place in yeast during fermentation
2. Takes place in the presence of oxygen
3. Produces energy only in the muscles of human beings
4. Produces ethanol, oxygen and energy.

Answer: 1. Takes place in yeast during fermentation

Class 10 Biology Notes For Respiration Long Answer Type Questions

Question 1. Explain how the exchange of gases occurs in plants across the surface of stem, root and leaves.
Answer:

1. Young Stems and Leaves. Through stomata between the atmosphere and intercellular spaces present in leaves and young stems. During daytime oxygen is passed out of them and carbon dioxide is absorbed. During night the reverse exchange of gases occurs.
2. Young Roots. There are no pores or stomata. The epiblema and root hairs are permeable to gases so the exchange of gases occurs between intercellular spaces of roots and the soil interspaces.
3. Old Stems and Old Roots. Lenticels or permanently open pores occur over the surface of old stems and roots. They are connected internally to intercellular spaces.
   • The exchange of gases occurs between the atmosphere and plant interior through the lenticels which have loosely held complementary cells.

Life Processes Class 10 Biology Transportation Notes

What is transportation? What is its importance?

It is the carrying of materials from one part to another of the body. Materials are carried from the region of their availability to the region of their consumption, storage or elimination.

Transportation Importance

1. Food. Every cell of the body requires food. It is passed on from the area of synthesis (in plants) or availability (alimentary canal in animals) to all parts of the body through the transport system.
2. Oxygen. In animals, oxygen becomes available from the respiratory surface. It is passed on to various parts through transportation.
3. Carbon Dioxide. It is produced during respiration. It is carried to the respiratory surface by a transport system for elimination.
4. Waste Materials. Metabolic wastes like urea, uric acid and others are first taken to the kidneys for separation and then stored temporarily for elimination through transportation.
5. Water. It circulates in the body through a transportation system.
6. Hormones. They are poured into the transport system for passage to the area of use.
7. Minerals. They are passed from the region of availability to all the parts for utilisation.
8. Other Functions. The transportation system has an accessory function of defence against pathogens and plugging the place of injury.

class 10 transportation notes

Transportation in Human Beings

Human beings have a circulatory system for transportation. It consists of a pumping heart, circulatory fluids blood and lymph and tubes. Depending upon the fluid being circulated, the circulatory system is of two types, blood blood-vascular system and the lymphatic system. The blood-vascular system comprises blood, blood vessels and the heart.

Life Processes Class 10 Biology Transportation Notes Heart Beat

What is Heartbeat? How pulse is different from a heartbeat?

It is a rhythmic contraction (systole) and expansion (diastole) of the heart. The rate is 70-72/ minute for adult human males and about 80/minute for adult females. Heartbeat is listened to by an instrument called a stethoscope.

Heartbeat has a low-pitched sound of a longer duration called lubb and a high-pitched shorter duration sound called dup. Lubb represents the simultaneous closure of auriculo-ventricular valve while dup is due to the simultaneous closure of semilunar valves.

Pulse. It is a rhythmic throb felt by a finger over a superficially placed artery (e.g., radial artery below the base of the thumb). Its value is equal to the heartbeat.

Types of Blood Circulation

What is double circulation? Give one importance.

Fishes possess a single blood circulation— venous blood → heart → Gills → Body → Venous blood. An incomplete circulation occurs in amphibians and lizards where mixed blood passes into the body for supply as well as lungs for oxygenation. A complete double circulation occurs in birds and mammals including human beings.

Double Circulation. It is a passage of the same blood twice through the heart, once in a deoxygenated form on the right side and then on the left side in an oxygenated state. The two components of double circulation are pulmonary circulation and systematic circulation.

class 10 science notes biology

1. Pulmonary Circulation. It is a short distance blood circulation from the heart to the lungs and back. Deoxygenated blood collects in the right auricle, is pumped into the right ventricle and from there to the pulmonary trunk.

The latter forms two pulmonary arteries which go to the lungs. In the lungs, the blood is oxygenated. Oxygenated blood flows to the left auricle by means of two pairs of pulmonary veins.

2. Systemic Circulation. It is a long-distance circulation of blood from the heart to all parts of the body except the lungs. The blood circulated by it is oxygenated. This blood becomes deoxygenated in the body tissues.

• From there the deoxygenated blood is carried by veins to the right atrium of the heart through a recall, a postcard and a coronary sinus. Nutrients, waste products and other materials are also transported in the process.
• Importance of Double Circulation. Double circulation, as found in birds and mammals, is the most efficient pathway of blood circulation. It provides 100% oxygenated blood to various body parts. The deoxygenated blood is sent by pulmonary circulation to the lungs for complete oxygenation.
• This is helpful for the thermoregulation of the body and the availability of maximum energy for body activities. Animals with incomplete double circulation (amphibians and reptiles) are unable to regulate the temperature of their body.
• Fishes with single circulation use partially oxygenated blood in most parts of their body. They are also unable to regulate their body temperature.

The Tubes: Blood Vessels

Human blood flows only inside closed blood vessels. The latter are of three types-arteries, veins and capillaries.

Arteries. They carry blood coming from the heart to various parts of the body. They are thus distributing blood vessels. Since the blood is coming from the heart, it flows rapidly but with jerks due to alternate expansions.

• The wall is thick and elastic due to the thickening of the middle tunica media. The lumen is narrow. Valves are absent. Most arteries are deep-seated except a few like radial where pulse can be felt. Except for pulmonary arteries, all other arteries cany oxygenated blood. Empty arteries do not collapse.

Veins. They carry blood from various parts of the body towards the heart. They are, therefore, collecting blood vessels. Blood flow is slow but smooth. Internal valves prevent the backflow of blood.

• The wall is moderately thickened as tunica media is a little thickened. The lumen is wide. The empty veins collapse. Most veins are superficial. They carry deoxygenated blood except in pulmonary veins.
• Capillaries. They are narrow (4-10 pm) blood vessels having a single-layered wall which occur in contact with tissues inside all body organs. They are meant for the exchange of materials between blood and body cells.

class 10 excretion notes

• For this blood capillaries have fine pores from which some plasma, dissolved substances and even some WBCs come out. It is called a capillary exchange. The reverse flow from cells also occurs.
• The capillary formation is a device to help in the exchange of materials. An artery branches to form arterioles while each arteriole gives rise to several capillaries. The capillaries reunite to produce venules which join to form veins.

Life Processes Class 10 Biology Transportation Notes Blood Pressure

What is blood pressure? Define systolic and diastolic pressure.

The pressure exerted by blood on the wall of an artery is called blood pressure. The instrument used in measuring blood pressure is called a sphygmomanometer. It has a mercury manometer, an inflatable cuff, and a compressible rubber bulb with a screw for pumping and releasing air.

A stethoscope is required. The rubber cuff is wrapped around the upper arm just above the elbow. It is inflated. The diaphragm of the stethoscope is placed over the brachial artery in the fold of the elbow. Air is very slowly released. The first sound of blood flowing in the brachial artery gives systolic pressure.

biology chapter 6 class 10 notes

With the further release of air, a point is reached when the sound of flowing blood disappears. It is diastolic pressure. For a normal young person, the two values are 120 mm Hg (systolic) and 80 mm Hg (diastolic).

A higher value, say 140/90 mm Hg is hypertension (high blood pressure) while a lower value, say 110/70 mm Hg, is hypotension (low blood pressure).

Maintenance By Platelets

How do the platelets minimise the leakage of blood from an injured blood tube?

• At the place of injury, the injured blood vessel begins to spill blood. Besides loss of blood, there is a fall of blood pressure which is harmful to the working of the body. Blood platelets (thrombocytes) help in sealing the place of injury.
• On exposure, the platelets release thromboplastin. In the presence of calcium, thromboplastin acts on the prothrombin of blood to form a proteolytic enzyme called thrombin.
• Thrombin acts on blood protein fibrinogen to form insoluble fibrin monomers. Fibrin monomers undergo polymerization. They form long fibres which give rise to a fine network at the place of injury.

” life processes notes”

• It entraps blood corpuscles. A jelly-like mass called a blood clot is formed. The clot contracts brings the injured walls together and seals the area. A liquid called serum is released during the solidification of the clot.
• It is straw coloured second transport fluid of the body. Lymph is derived from tissue fluid. It is picked up by lymph capillaries which join to form larger lymph vessels. Tissue fluid continues to increase in quantity due to pressure filtering in the blood capillaries.
• Excess of tissue fluid passes out as lymph. Lymph is devoid of red blood corpuscles and blood platelets. It has a small number of leucocytes. Protein content is also less. Lymphocytes (a type of leucocytes) are in good numbers.
• They actually mature in special areas attached to lymph vessels which are called lymph nodes and lymph-containing organs. Lymph-containing organs are adenoids, tonsils, thymus and spleen.
• Lymph capillaries are more permeable than blood capillaries. Therefore, most of the organs pour their secretions into the lymph. In the intestine, lymph vessels called lacteals are involved in the absorption of fat Lymph vessels join to form larger ducts which open into right and left subclavian veins.
• Like veins, movement of lymph in lymph vessels occurs through the milking action of surrounding muscles. Lymph vessels also possess valves, like veins, to prevent backflow of lymph.

Lymph Functions

Blood Volume. Lymph maintains the blood volume of the body which has a tendency to decrease due to plasma filtration in tissues,

1. Middleman. Lymph acts as a middleman between tissues/glands and blood,
2. Fat. Digested fat is collected by lymph for passing into blood.
3. Lymphocytes. They mature in lymph nodes,
4. Germs. Lymph capillaries and lymph nodes attract and destroy germs.

notes for biology class 10

Life Processes Class 10 Biology Transportation Notes Multiple Choice Questions

Which one of the following statements is correct about the human circulatory system?

1. Blood transports only oxygen and not carbon dioxide
2. The human heart has five chambers
3. Valves ensure that the blood does not flow backwards
4. Both oxygen-rich and oxygen-deficient blood get mixed up in the heart.

Answer: 3. Valves ensure that the blood does not flow backwards