Class 8

UP Board Notes For Class 8 Science Chapter 7 Conservation Of Plants And Animals

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Conservation Of Plants And Animals Chapter In A Nutshell

  • The flora and fauna of a place together form the biodiversity of a place.
  • The cutting down of trees on a large scale for various purposes is called deforestation.
  • Deforestation occurs due to both natural and man-made causes.
  • One of the major causes of deforestation is the use of trees in the paper industry.
  • It takes about 17 full-grown trees to produce one tonne of paper. Thus, we should save, reuse, and recycle paper.
  • Deforestation has various adverse effects on the environment.
  • The restocking of forests by planting new trees is called reforestation.
  • IUCN (International Union for Conservation of Nature and Natural Resources) has created five categories for the conservation of biodiversity. These categories are extinct, endangered, vulnerable, rare, and critically endangered species.
  • Red Data Book is a source that keeps a record of all endangered plants and animals.
  • The government lays down rules, methods, and policies to protect and conserve forests and animals.
  • Various protected areas like sanctuaries, national parks, and biosphere reserves are earmarked for conservation of biodiversity.
  • The Forest Conservation Act, 1927, and Wildlife Protection Act, of 1972 deal with the conservation of forests and wild animals respectively. The main aim of these acts is to preserve and conserve our biodiversity.
  • Migratory birds fly to faraway areas during a particular time of the year because of inhospitable climatic conditions in their habitat.

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Conservation Of Plants And Animals Important Terms And Definitions

Biodiversity: All the living organisms of an ecosystem are together referred to as biodiversity.
Desertification: Desertification is the process by which fertile land loses fertility and gets converted
into desert as a result of deforestation.
Ecosystem: An ecosystem is an interactive system in which all biotic and abiotic components interact
with each other as well as with the environment.
Endangered Species: The species in danger of extinction due to rapid decline in their number and
change in their habitat are called endangered species.
Endemic Species: The species unique to a particular habitat are called endemic species.
Extinct Species: A species is called an extinct species when the last existing member of the species
dies.
Fauna: All the plant species found in a particular habitat are referred to as fauna.
Flora: All the animal species found in a particular habitat are referred to as flora.
Migration: Migration is the regular or systematic movement of a group of organisms in search of
suitable temporary shelter.
Species: A group of a population capable of interbreeding is called a species.

Deforestation

Answer. A major threat to the survival of plants and animals on the Earth is deforestation. Deforestation has adverse effects on the food chains. Deforestation results in increased levels of carbon dioxide in the atmosphere. This results in an increase in the temperature of the Earth and consequently leads to global warming. A decrease in the number of trees and forests results in decreased rainfall. This disturbs the water cycle which leads to drought. Deforestation is also responsible for the change in the physical properties like nutrient content, texture, etc. of the soil. Deforestation exposes the topsoil to agents like wind and water that are responsible for soil erosion. Deforestation also affects the water-holding capacity of the soil.

Human beings are the main cause of deforestation. Forests are cleared to use land for the cultivation of crops, the construction of houses, roads, factories, etc. Forest fire and drought are some natural causes of deforestation.
Hence, reforestation must be practiced to retain the green wealth for future generations.

Conservation Of Plants And Animals Activity 1

Aim: To list the causes of deforestation and classify them as natural and man-made
Observation:

UP Board Notes for Class 8 Science Chapter 7 Conservation Of Plants And Animals Natural Causes Of Deforestation And Man Made Causes Of Deforestation

Conclusion:
Deforestation occurs due to both natural and man-made causes.

Conservation of Plants and Animals Activity 2

Aim: To list various effects of deforestation on animals
Observation: Effects of deforestation on animals are:
1. Loss of habitat
2. Shortage of food
3. Disturbance of food chain
4. Increased risk of natural calamities and hunters

Conservation of Plants and Animals Objective Type Questions

A. State whether the following statements are true or false.

  1. Habitat destruction is a major threat to biodiversity.
  2. Forests are mostly cut for their leaves.
  3. Deforestation ruins the ecology of a region and destroys a large portion of the life forms that live there.
  4. Forests shelter a variety of plants and animals.
  5. Forest conservation is the management of rivers to save the environment.

Answers:

  1. True
  2. False
  3. True
  4. True
  5. False

B. Fill in the blanks.

  1. The large-scale cutting of trees and clearing of forests is called_______
  2. Deforestation reduces the amount of water in the soil and lowers the______
  3. Depletion of forests leads to a decrease in_______fertility.
  4. If all plants in a forest are cut, it will lead to soil______
  5. Establishing a new forest on land that had been deforested earlier is called_____

Answer:

  1. Deforestation
  2. Water table
  3. Soil
  4. Erosion
  5. Afforestation

Conservation Of Plants And Animals Short Answer Type Questions

A. What do you mean by desertification?

Answer. Soil erosion exposes the lower, hard and rocky layers. This soil has less humus and is less fertile. Gradually the fertile land gets converted into deserts. It is called desertification.

Loss of Biodiversity

Answer. The huge variety of flora and fauna on the earth is termed as biodiversity. Some of the major causes of loss of biodiversity are deforestation, land degradation and overexploitation of resources. Some species of plants and animals are found exclusively in a particular geographical area. Such species are called endemic species. The destruction of habitat or introduction of new species may affect the natural habitat of an endemic species IUCN (International Union for Conservation of Nature and Natural resources) evaluates the status of threat to a species based on available information. It has identified five categories of animals and plants that need protection. A Red Data Book is a record of all threatened species of plants and animals.

Conservation Of Plants And Animals Objective Type Questions

A. State whether the following statements are true or false.

  1. The IUCN Red List has information about species that do not exist.
  2. Endangered animals are not seen on the earth anymore.

Answers: 1. False 2. False

B. Fill in the blanks.

  1. Red data book is a list of______species.
  2. The species found only in a particular area is known as______

Answers: 1. Threatened 2. Endemic species

C. Multiple Choice Questions.

1. What are critically endangered species?

  1. Species having an extremely high risk of becoming extinct.
  2. Species with high chances of moving into the endangered category.
  3. Species with huge populations.
  4. Species that do not exist anymore.

Answer: 1. (1) Species having an extremely high risk of becoming extinct

2. The species that exist in small numbers are called_______

  1. Threatened species
  2. Rare species
  3. Endangered species
  4. Critically Endangered

Answer.(2) Rare species

3. Which of the following bird have become extinct?

  1. Dodo
  2. Pigeon
  3. Bat
  4. Gesse

Answer.(1) Dodo

Conservation Of Plants And Animals Short Answer Type Questions

A. What is biodiversity conservation?

Answer. Biodiversity is protection and scientific management of biodiversity so as to maintain it at its optimum level and derive sustainable benefits for present as well as future generations.

Conservation of Forest and Wildlife

Answer. The Government of India has created some protected areas such as national parks, wildlife sanctuaries and biosphere reserves to protect flora and fauna and their habitats.
National parks are protected land areas preserved in natural conditions to provide natural habitat to wildlife. An example of a national park is Jim Corbett national park, Uttarakhand.
Wildlife sanctuary is an area where only animals are protected and their capturing and killing is strictly prohibited. However permission for collection of minor forest products, harvesting of timber and
cultivation is granted.

A biosphere reserve is a large protected area for the conservation of wildlife, plant and animal resources. The main aim of the biosphere reserves is to conserve biodiversity, maintain ecological balance, and maintain the culture of that particular area. A biosphere reserve may contain National Parks and Sanctuaries. For example, Pachmarhi Biosphere Reserve includes Satpura National Park, Bori Sanctuary and Pachmarhi Wildlife Sanctuary.

Zoological park also referred to as a ‘zoo’, is a place where animals are protected by keeping them in special enclosures and cages for public exhibition. Botanical garden is a place where a wide variety of plants are cultivated for scientific, educational, and ornamental purposes. It often includes a library, a herbarium, greenhouses and an arboretum.

Conservation Of Plants And Animals Objective Type Questions

A. State whether the following statements are true or false.

  1. Kanha National Park is in Madhya Pradesh.
  2. A biosphere reserve is an international designation for conservation.

Answers: 1. True 2. False

B. Multiple-Choice Questions

1. Which of the following biosphere reserves is a part of MAB program?

  1. Nokrek
  2. Pachmarhi
  3. Nanda Devi
  4. Bori

Answers. (3) Nanda Devi

2. Wildlife protection act was enacted in which year?

  1. 1967
  2. 1970
  3. 1992
  4. 1972

Answers. (4) 1972

3. Where is Jaldapara Sanctuary located in India?

  1. (West Bengal
  2. Madhya Pradesh
  3. Maharashtra
  4. Andhra Pradesh

Answers: (4) Andhra Pradesh

C. Fill in the blanks.

  1. Jim Corbett National Park is situated in_____
  2. Gir Sanctuary is located in_______ and is famous for_______

Answer: 1. Uttrakhand 2. Gujarat, lion

Conservation Of Plants And Animals Short Answer Type Questions

A. List some important national parks in India.

Some important national parks in India are:

  • Kanha National Park, Madhya Pradesh
  • Betla National Park, Jharkhand
  • Tadoba National Park, Maharashtra
  • Simplipal National Park, Orissa

B. Name at least seven wild animals of Khangchendzonga National Park, which face the danger of extinction.

Answer. Wild animals of Khangchendzonga National Park which face extinction are snow leopard, clouded
leopard, marbled cat, Himalayan black bear, red panda, Tibetian wild ass, blue sheep, serow, goral, takin, musk deer, and green pigeon.

Conservation Of Plants And Animals Textbook Exercises

1. Fill in the blanks.

  1. A place where animals are protected in an artificial habitat is called a______
  2. Species found only in a particular area are known as_______
  3. Migratory birds fly to faraway places because of_______changes.

Answer: (1) Zoo (2) Endemic species (3) Climatic

2. Differentiate between the following:

  1. Wildlife sanctuary and biosphere reserve
  2. Zoo and wildlife sanctuary
  3. Endangered and extinct species
  4. Flora and fauna

(a) Differences between Wildlife sanctuary and Biosphere reserve are:

Wildlife Sanctuary

A wildlife sanctuary is an area where only animals are protected and their capturing and killing is strictly prohibited.

Biosphere Reserve

A biosphere reserve is a large protected area for the conservation of wildlife, plant, and animal resources.

(b) Differences between Zoo and Wildlife sanctuaries are:

Zoo

A zoological park also referred to as a ‘zoo’, is a place where animals are protected by keeping them in special enclosures and cages for public exhibition.

Wildlife Sanctuary

A wildlife sanctuary is an area where only animals are protected and their capturing and killing is strictly prohibited.

(c) Differences between endangered and extinct species are:

Endangered Species

The species in danger of extinction due to rapid decline in their number and change in their habitat are called endangered species.

Extinct Species

A species is called an extinct species when the last existing member of the species dies.

(d) Differences between flora and fauna are:

Flora
All the plant species found in a particular habitat are referred to a flora.

Fauna

All the animal species found in a particular are referred to a flora.

3. Discuss the effect of deforestation on the following.

  1. Wild animals
  2. Environment
  3. Villages (Rural areas)
  4. Cities (Urban areas)
  5. Earth
  6. The next generation

Answer.

  1. Deforestation destroys the natural habitat of wild animals and thus, they can become endangered.
  2. Deforestation decreases the level of oxygen in the atmosphere. The rainfall and fertility of soil also decrease due to deforestation. As a result, there are increased chances of natural calamities like floods and drought.
  3. Most of the agriculture is done in rural areas. Deforestation leads to a change in soil properties, which in turn affects the agriculture.
  4. In cities, there are many factories and automobiles. Deforestation further pollutes the environment and hence, the life in cities will not be healthy for living.
  5. Deforestation leads to an increase in the temperature of the earth causing global warming. Less trees would result in more soil erosion.
  6. Deforestation leads to climatic changes which has a great effect on the next generation. So, the next generation would not be as prosperous as the previous one.

4. What will happen if

  1. we go on cutting trees?
  2. the habitat of an animal is disturbed?
  3. the top layer of soil is exposed?

Answer.

  1. If we go on cutting trees continuously, rainfall and fertility of the soil will decrease. Hence, there are increased chances of natural calamities such as floods and drought. If the habitat of an animal is disturbed, some of the species will not get appropriate food and shelter and with the passage of time, they will come under the category of endangered species.
  2. If the top layer of the soil is exposed, the soil will have less humus and will become less fertile. Gradually, the land will convert into desert. This is called desertification.

5. Answer in brief

  1. Why should we conserve biodiversity?
  2. Protected forests are also not completely safe for wild animals. Why?
  3. Some tribals depend on the jungle. How?
  4. What are the causes and consequences of deforestation?
  5. What is a Red Data Book?
  6. What do you understand by the term migration?

Answer.

  1. We should conserve biodiversity to save flora and fauna from extinction.
  2. Protected forests are also not completely safe for wild animals because people living in the neighbourhood encroach upon them and harm them.
  3. Certain tribes depend on jungle for food, shelter and fuel.
  4. Human beings are the main cause of deforestation. Forests are cleared to use land for the cultivation of crops, construction of houses, roads, factories etc. Forest fire and drought are some natural causes of deforestation. Deforestation has adverse affects on the food chains. Deforestation results in increased levels of carbon dioxide in the atmosphere. This results in the increase in temperature of the Earth and consequently leads to global warming. Decrease in the number of trees and forests results in decreases rainfall. This disturbs the water cycle which leads to drought. Deforestation is also responsible for the change in the physical properties like nutrient content, texture, etc. of the soil. Deforestation exposes the top soil to agents like wind and water that are responsible for soil erosion. Deforestation also affects the water holding capacity of the soil.
  5. Red Data Book is a record of all threatened species of plants and animals. It is published by the International Union for Conservation of Nature and Natural resources (IUCN), which is now known as World Conservation Union (WCU). The red-listing assessment is a simple logical process to determine the status of threat to a species based on available information.
  6. The seasonal, mass movement of animals from one place to another to escape from extreme cold, to breed or to find food is called migration.

6. In order to meet the ever-increasing demand in factories and for shelter, trees are being continually cut. Is it justified to cut trees for such projects? Discuss and prepare a brief report.

Answer. It is not justified to cut trees for such projects.
When trees are cut down, the level of carbon dioxide in the atmosphere goes up, which results in the increase in temperature and consequently leads to global warming. Trees bring rain. So, the decrease in number of trees results in decreasing rainfall. Cutting down of trees is also responsible for the change in physical properties like nutrient content, texture of the soil.

7. How can you contribute to the maintenance of green wealth of your locality? Make a list of actions to be taken by you.

Answer.

For maintenance of green wealth in our locality, we shoul

  • Grow more and more trees on both sides of the road.
  • Discourage the cutting of trees.
  • Maintain greenery in the parks of our locality.
  • Water the plants in our locality regularly
  • Convince other people to plant new trees.
  • Take out rallies to create awareness among people.
  • Coordinate with local authorities for proper help.

8. Explain how deforestation leads to reduced rainfall.

Answer. Trees lose water by the process of transpiration. This water contributes a lot towards atmospheric moisture. Thus, green plants have major contribution in precipitation and rainfall pattern. So,\ deforestation leads to reduced rainfall.

9. Find out about the national parks in your state. Identify and show their locations in the outline map of India.

Some of the national parks of India are marked on the map

UP Board Notes for Class 8 Science Chapter 7 Conservation Of Plants And Animals Some of the national parks of India are marked in the map

10. Why should paper be saved? Prepare a list of ways by which you can save paper.

Answer. By wasting paper products, we waste forests. The more paper we use, the more trees we need to cut down to feed our insatiable appetite for paper. In order to reduce deforestation, we must learn to recycle used paper, efficiently and economically.

Ways by which paper can be saved are:

  • Collect used paper and recycle it.
  • Use both sides of a paper for writing.
  • Spread awareness about the importance of paper.
  • Use paper intelligently.
  • Old envelopes can also be used for doing the rough work.
  • Schools should encourage online submission of reports and assignments so that papers can be saved.
  • Don’t take a printout unless it is absolutely necessary.

11. Complete the word puzzle.

Down:

  1. Species on the verge of extinction.
  2. A book carrying information about endangered species.
  3. Consequence of deforestation.

Across

  1. Species which have vanished.
  2. Species found only in a particular habitat.
  3. Variety of plants, animals, and micro-organisms found in an area.

UP Board Notes for Class 8 Science Chapter 7 Conservation Of Plants And Animals Cross And Down

Down:
1. Endangered
2. Red data book
5. Deserts
Across:
1. Extinct
3. Endemic
4. Biodiversity

Conservation of Plants and Animals Hots corner

A. People living in hilly areas are cutting down a lot of trees for their daily needs and agricultural purposes. After a few years they face a lot of landslides in their area. What do you think is the reason behind it?

Answer. Cutting down of trees on a large scale is one of the main reasons behind the landslides. The roots of the trees hold the soil. As a result of deforestation, the soil gets loose and runs off during heavy rain resulting in landslides.

B. Suppose in a forest the number of carnivorous animals suddenly increases than the number of herbivore animals. What will be the consequences?

Answer. If the number of carnivorous animals increases as compared to the number of herbivore animals, then there will be a shortage of food for the carnivores and soon they will die due to hunger. There will be a bloom of plants also.

Practice exercise

A. Fill in the blanks.

  1. The Indian Giant Squirrel is_______ fauna.
  2. A species with a very small population on the earth is called_______species
  3. ______ is a protected area where only animals are protected.
  4. Project Tiger was launched in India in the year_______
  5. A_______ is much larger than a national park or a sanctuary.

Answers:

  1. Endemic
  2. Rare
  3. Wildlife Sanctuary
  4. 1973
  5. Biosphere Reserve

B. State whether the following statements are true or false.

  1. Deforestation results in desertification.
  2. Deforestation has disastrous effects on the biodiversity of a place.
  3. Siberian cranes come to India during winter.
  4. Man is not responsible for deforestation.
  5. Climatic changes do not affect biodiversity.

Answer:

  1. True
  2. True
  3. True
  4. False
  5. False

C. Answer the following in one word.

  1. Asiatic lion and pink pigeon belong to which IUCN category?
  2. Which form of wood is used to make paper?
  3. Name an extinct flightless bird.
  4. Which term is used for species that are likely to become endangered shortly?
  5. Which bird covers the longest migration distance?

Answer:

  1. Endangered
  2. Pulp
  3. Dodo
  4. Vulnerable
  5. Arctic tern

Conservation Of Plants And Animals Short Answer Questions

1. Write a short note on biosphere reserve.

Answer. The concept of a Biosphere Reserve has been evolved by the Man and Biosphere (MBA) program of UNESCO. In a biosphere reserve, multiple land use is allowed by designating various zones such as core, buffer zone, and manipulation zone. In a biosphere reserve, wild population, traditional lifestyle of tribals, and varied domesticated plant and animal genetic resources are protected.

 

UP Board Notes For Class 8 Science Chapter 5 Coal And Petroleum Science

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Coal And Petroleum Science Chapter In A Nutshell

  • Resources obtained from nature are known as natural resources, for example, air, soil, minerals, etc.
  • Natural resources can be classified into two types: exhaustible and inexhaustible natural resources. Exhaustible natural resources are present in a limited quantity, cannot be replaced within a reasonable period of time and can be exhausted by human activities. Petroleum, coal, forests, etc., are examples of exhaustible natural resources.
  • Inexhaustible natural resources are present n an unlimited quantity, can be replaced within a reasonable period of time and cannot be exhausted by human activities, for example, air and sunlight
  • Coal is an exhaustible natural resource. It is formed by the decomposition of plants buried under the Earth in conditions of high pressure and extreme temperatures. The process of conversion of dead vegetation into coal is called carbonisation.
  • There are four varieties of coal namely, peat Ignite, bituminous and anthracite.
  • Coal deposits in India are found in Jharkhand, Orissa, Madhya Pradesh and West Bengal.
  • Coal is used as a domestic and industrial fuel, in the manufacturing of synthetic petrol and synthetic natural gas, extraction of metals from their ores, thermal power plants and is
  • Petroleum, another exhaustible natural resource, is formed from the dead bodies of organisms that settled at the bottom of the sea millions of years ago and got covered with layers of sand and clay. In the absence of air and under high pressure and temperature, these dead bodies get converted into petroleum.
  • Oil wells in India are located in Ankleshwar and Kalol in Gujarat; Rudrasagar and Lake in Assam; Bombay High; and deltas of Cauvery, Krishna and Godavari rivers.
  • The process of separating various constituents of petroleum is known as refining and it is done in the petroleum refineries.
  • In India, Petroleum refineries are located at Mumbai, Chennai, Mathura, Barauni. Digboi, Guwahati, Haldia, etc.
  • Petrol and diesel, which are obtained from petroleum, are used as fuel. Petroleum is used for making lubricants, medicines, ointments, metalling roads, etc.
  • natural Gas, another exhaustible natural resource, is formed by the decomposition of vegetable matter lying underwater in the conditions of high temperature, high pressure and absence of oxygen.
  • Natu-‘al gas is used as a domestic and industrial fuel, in fertiliser industry and as fuel for the transport industry.
    natural gas is a clean fuel and produces less pollution. It has high calorific value.
  • Many useful substances, known as petrochemicals, are obtained from petroleum and natural gas. They are used in the manufacturing of detergents, man-made fibres, plastics, etc.
    Since fossil fuels are exhaustible sources of energy, we should not waste and misuse fossil fuels. One should move towards the alternative or renewable sources of energy such as solar, wind and biomass energy.

Read and Learn More UP Board Notes for Class 8 Science

Coal And Petroleum Science Important Terms And Definitions

Fuels: A substance that can be used to produce neat at a reasonable cost is called a fuel.
Fossil fuels: Fuels formed from the dead remains of plants and animals, w hich remained buried deep under the Earth for millions of years. Coal, petroleum and natural gas are fossil fuels.
Coal: It is a hard, black or brownish-black sedimentary rock containing more than 50% of carbon by weight. Along with carbon, it contains hydrogen, oxygen, nitrogen, sulphur, etc.
Crude oil: It is a mixture of several solid, liquid and gaseous hydrocarbons mixed with water, salt and other particles.
Petroleum: It is a fossil fuel, which is dark, viscous, oily, strong smelling and known as black gold. Petrol and diesel are obtained from petroleum.
Natural gas: It is a very important fossil fuel, which mainly consists of methane and occurs deep under the cost of the Earth either alone or along with crude oil. It is stored under high pressure and is hence, called Compressed Natural Gas or CNG.
Coal gas: It s obtained during the process of making coke from coal. Coal gas is a mixture of hydrogen, methane, carbon monoxide and other gases.
Coal tar: It is a thick, black, opaque fluid, which is obtained as a by-product of the process of manufacturing coke.
Coke: It is a hard, dry fuel produced by heating coal to a very high temperature in the absence of air. It has very high carbon content and is used as a fuel.

Types of Natural Resources

Resources obtained from nature are known as natural resources, for example, air, water, minerals, etc. Natural resources are of two types: exhaustible and inexhaustible natural resources. Petroleum, coal, forests, etc. are examples of exhaustible natural resources and air and sunlight are inexhaustible naturals! resources.

Coal And Petroleum Science Activity 2

Aim: To show that as the number of consumers increases, the quantity of resources available decreases.
Procedure:
1. Fill a few containers with popcorn, peanuts, roasted gram and toffees.
2. Divide students into groups of seven each.
3. Further divide each group into three sub-groups containing 1,2 and 4 students.
4. Label these sub-groups as first, second and third generations respectively.
5. Put one full container for each group on a table.
6. Ask students or consumers of the first geneation to eat from the containers.
7. Next, ask students or consumers of the second generation to eat from the containers.
8. Next, ask students or consumers of the third generation to eat from the containers.

Observation: The quantity’ of the food available dwindled with each generation of students or consumers.
Conclusion: With each generation, the number of consumers increase and the quantity of resources available becomes less.

Coal And Petroleum Science Objective Type Questions

A. State whether the following statements are true or false.

1. Fossil fuels are formed from dead remains of plants and animals.
2. Forests are inexhaustible natural resources.
3. Exhaustible natural resources can be replenished within a reasonable amourt of time.
4. Coal is an exhaustible natural resource.
5. CNG is a man-made fuel.

Answers: 1. True 2. False 3. False 4. True 5. False

B. Fill in the blanks.

1. A substance that can be used to produce heat energy at a reasonable cost is known as a____
2._____and are exhaustible natural resources.
3. ____ is formed by the decomposition of plants buried under the Earth in conditions of high Dressure and extreme temperatures.
4.____natural resources are present in a limited quantity and can be exhausted by human activities.

Answers: 1. Fuel 2. Petroleum, coal, forests 3. Coal 4. Exhaustible

Coal

Answers. Coal is a hard, black or brownish-black sedimentary rock containing more than 50% carbon by weight Coal comes in four varieties — peat lignite, bituminous and anthracite. Plants that remain buried under the Earth in conditions of high pressure and extreme temperatures over millions of years converts into coal. This process is called carbonisation. Coal is used as a domestic and industrial fuel. It is processed to form coal gas, coal tar and coke. Coal gas is obtained during the process of making coke from coal.

Coal And Petroleum Science Objective Type Questions

A. State whether the following statements are true or false.

1. Coal contains more than 50% of carbon by weight.
2. Coal tar is formed from petroleum.
3. Bituminous is a variety of coal.
4. Coal is processed to form coal tar.

Answers: 1. True 2. False 3. True 4. True

B. Fill in the blanks.

1. Coal is formed over millions of years by decomposition of plants buried under the Earth in conditions of high____ and____
2.______is obtained during the process of making coke from coal.
3.Coal is used as a_____ and____ fuel.

Coal And Petroleum Science Short Answer Type Questions

A. What is coal tar used for?

Answers. Coal tar is a mixture of about 200 substances. It is used for metalling roads and in the manufacturing of synthetic dyes, perfumes, explosives, photographic materials, plastics, paints, roofing materials, naphthalene balls, etc.

B What is carbonisation?

Answers. The Process of formation of coal by the decomposition of plants buried under the each in conditions of high pressure and extreme temperatures is called carbonisation.

Coal And Petroleum Science Long Answer Type Questions

A. Give few uses of coal.

Answers. Coal is used as a fuel in homes and in industries to run steam engines and to produce electricity in thermal power plants. Products obtained from coal are coke, coal gas and coal tar. Coke is used in the manufacture of steel and extraction of metals. Coal gas is used as a fuel and more than 200 products are obtained from coal tar. These products are used for manufacturing synthetic dyes, paints, perfumes, naphthalene balls, photographic materials, etc.

Petroleum

Answers. Petroleum is a dark, viscous, oily, strong-smelling liquid, which is also known as black gold. Petrol and diesel are obtained from petroleum. Petroleum is formed from the organisms whose dead bodies settled at the bottom of seas or oceans and got covered with layers of sand and clay. In the absence of air and under high pressure and temperature, these dead bsdies got converted into petroleum. The process of separating various constituents of petroleum is known as refining and t is done in petroleum refineries.

UP Board Notes For Class 8 Science Chapter 5 Coal And Petroleum Science constituents petroleum and their uses

Coal And Petroleum Science Objective Type Questions

A. State whether the following statements are true or false.

1. Petrol and diesel are obtained from petroleum.
2. Petroleum is formed in the absence of air over millions of years.
3. There are no petroleum refineries in India.
4. Paraffin wax is obtained from coal.
5. The process of separating the various constituents of petroleum is known as refining.

Answers: 1. True 2. True 3. False 4. False 5. True

B. Match the items in column A with those in column B.

UP Board Notes For Class 8 Science Chapter 5 Coal And Petroleum Science Match the items in column A with those in column B

Coal And Petroleum Science Short Answer Type Questions

A. How are various constituents of petroleum obtained?

Answers. Various constituents or fractions of petroleum are separated in a Process known as refining of petroleum and it is done in petroleum refineries.

B. List the various constituents of petroleum.

Answers. The constituents of petroleum are LPG, petrol, diesel, kerosene, lubricating oil, paraffin wax and bitumen.

Coal And Petroleum Science Long Answer Type Questions

A. State the uses of at least three constituents of petroleum.

Answers.

Petrol, paraffin wax and diesel are the three constituents of petroleum.
1. Petrol is used as a motor fuel. It is also used for dry cleaning.
2. Paraffin wax is used for making ointments, candles, Vaseline etc.
3. Diesel is used as a fuel for heavy motor vehicles and electric generators.

Natural Gas

Answers. Natural gas is a very important fossil fuel. It mainly consists of methane and occurs deep under the crust; of the Earth either alone or along with the crude oil It is stored under high pressure and is hence, called! Compressed Natural Gas or CNG. Natural gas is formed by the decomposition of vegetable matter lying underwater in conditions of high temperature, pressure and in the absence of oxygen. Natural gas; is used as a domestic and industrial fuel, in fertiliser industry and as fuel for the transport industry. It is a clean fuel and produces less pollution. Since fossil fuels are exhaustible sources of energy, we should not; waste and misuse fossil fuels. One should move towards the alternative or renewable sources of energy! such as solar, wind and biomass energy.

Coal And Petroleum Science Objective Type Questions

A. State whether the following statements are true or false.

1. Natural gas is always found alone.
2. Natural gas mainly consists of methane and is stored under high pressure.
3. Petrochemicals are used for manufacturing detergents, plastics, etc.
4. Solar, wind and biomass energy are exhaust ble natural resources.

Answers: 1. False 2. True 3. True 4. False

B. Fill in the blanks.

1. Natural gas is formed in the absence of____
2. We should not_____or____fossil fuels.
3. _____is used in the fertiliser industry
4. Natural gas is a_____ fuel.

Answers: 1. Oxygen 2. Waste, misuse 3. Natural gas 4. Clean

Coal And Petroleum Science Short AnswerType Questions

A. Why natural gas is considered a clean fuel?

Answers. Natural gas bums with a smokeless flame and does not produce harmful gases such as carbon- monoxide. It has a high calorific value. Hence, natural gas is called a clean fuel.

B. What are renewable sources of energy and why are they called so?

Answers. Air, wind, water and biomass are examples of renewable sources of energy. They are present in unlimited quantity or replenish themselves quickly through natural processes. Hence, they will not be exhausted by human activities. Such resources are therefore called renewable sources of energy.

Coal And Petroleum Science Long Answer Type Questions

A. Discuss the various types of gaseous fuels.

Answers.

Different types of gaseous fuels are:
1. Natural gas is found either alone or along with petroleum deep under the Earth’s crust It mainly contains methane.
2. Water gas is prepared by passing steam over red-hot carbon fuel such as coke. It contains carbon monoxide and hydrogen.
3. Coal gas is obtained as a by-product during the making of coke from coal. It is a mixture of hydrogen, methane, carbon monoxide and other gases.
4. LPG is liquefied and compressed before being filled in cylinders and hence, it is called liquefied Petroleum gas. It is an odourless gas but a chemical known as ethyl mercaptan, which has a foul smell, is added to it to assist n detecting leakages from cylinders.
5. CNG or compressed natural gas is a substitute for gasoline or diesel fuel. It is made by compressing methane extracted from natural gas.

Coal And Petroleum Science Textbook Exercises

Question 1. What are the characteristics of CNG and LPG as fuels?

Answers.

The characteristics of LPG and CNG are:

  • LPG and CNG have high calorific values.
  • (LPG burns with a smokeless flame and does not cause pollution. CNG also does not cause pollution. They do not produce any poisonous gases on burning.
  • They are easy to handle and convenient to store.
  • They undergo complete combustion.
  • They are both clean and environment-friendly fuels.

Question 2. Name the petroleum product used for surfacing roads.

Answers. Bitumen is the petroleum product used for surfacing roads.

Question 3. Describe how coal is formed from dead vegetation. What is this process called?

Answers. About 300 million years ago, forests got buried under the soil. They were compressed by soil deposits and their temperature raised as they sank deeper and deeper. Due to the high temperature and pressure, gradually the dead vegetation changed into coal and this process is known as carbonisation.

Question 4. Fill in the blanks.

  1. Fossil fuels are ____ ______and_____
  2. Process of separation of different constituents from petroleum is called_____
  3. Least polluting fuel for vehicles is______

Answers: (1) Coal, petroleum, natural gas (2) Refining (3) CNG (Compressed Natural Gas)

Question 5. Tick True/False against the following statements.

Answers.

  1. Fossil fuels can be made in the laboratory.
  2. CNG is a more polluting fuel than petrol.
  3. Coke is almost a pure form of carbon.
  4. CNG (Compressed Natural Gas)
  5. Coal tar is a mixture of various substances.
  6. Kerosene is not a fossil fuel.

Answers: (1) False (2) False (3) True (4)True (5) False

Question 6. Explain why fossil fuels are exhaustible natural resources.

Answers. Fossil fuels are formed from the remains of dead plants and animals. It takes millions of years for this process to take place. The known reserves of these fuels are limited and herce, these are exhaustible fuels.

Question 7. Describe the characteristics and uses of coke.

Answers. Coke is a pure form of carbon. It is tough, porous and black. Coke is used to manufacture artificial graphite, which is used in the manufacturing of calcium carbide, required for manufacturing acetylene gas. Acetylene gas is the basic raw material for manufacturing acetic acid and PVC. Acetylene is used for manufacturing water gas and producer gas, which are used as fuel. It is used to extract metals from their ores. Since coke does not produce any smoke, hence it is used as a household fuel.

Question 8. Explain the process of the formation of petroleum. 

Answers. Petroleum is formed from the bacterial decomposition of the remains of animals and plants, which got buried under the sea millions of years ago. When these organisms died, they sank to the bottom of the seas and oceans and got covered by sand and clay. Over a period of millions of years, in the absence of air. these organisms got converted into petroleum due to excessive heat and pressure. The hydrocarbons formed were trapped by impervious rocks forming an oil trap. Natural gas is usually found along with petroleum.

Question 9. The following table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.

UP Board Notes For Class 8 Science Chapter 5 Coal And Petroleum Science the total power shortage in India from 1991-1997

Coal And Petroleum Science Hotscorner

A. Which property of petroleum causes it to form a layer over water?

Answers. A liquid less dense than water will always float on water. Petroleum is less dense than water and hence, it forms a layer over water.

B. Why is petrol used in lightweight vehicles but diesel is used in heavy trucks?

Answers. Petrol has low ignition temperature and calorific value as compared to diesel. Thus, burning of diesel produces a large amount of energy. Hence, diesel is used as a fuel in heavy vehicles.

Coal And Petroleum Science Practice exercises
Objective Type Questions

A. Fill in the blanks.

1.______is usually found along with petroleum in the reservoirs under the ground.
2. Various useful products are separated from petroleum by_____
3. Petrol has a low______and____as compared to diesel.

Answers: 1. Natural gas 2. Refining 3. Ignition temperature, calorific value

B. Circle the odd one out.

1. Coal, petroleum, natural gas, cow dung cakes, kerosene
2. Jharkhand, Orissa, Ankleshwar, Madhya Pradesh, West Bengal
3. Cotton, detergents, polyester, nylon, plastics

Answers: 1. Cow dung cakes 2. Ankleshwar 3. Cotton

C. State whether the following statements are true or false

1. ‘When heated in air, coal burns and produces mainly carbon dioxide.
2. Coke is used in the extraction of steel.
3. Petrol is a mixture of several solid, liquid and gaseous hydrocarbons mixed with water, salt and other particles.
4. Coal tar is a thick, black, opaque fluid, which is obtained as a by-product of the process of manufacturing coke.

Answers: 1. True 2. True 3. False 4. True

D. Multiple Choice Questions.

Question 1. Which fuel is used in jet aircraft?

  1. Petrol
  2. Kerosene
  3. CNG
  4. Coal
    Answers. Kerosene

Question 2. ‘Which of the following is a non-polluting fuel for vehicles?

  1. Coal
  2. CNG
  3. Kerosene
  4. DieselAnswers. 1) CNG

Question 3. Which petroleum product is used for surfing roads?

  1. Coal Tar
  2. Paraffin wax
  3. Bitumen
  4. PetrochemicalsAnswers. 3)Bitumen

Question 4. Which of the following is the best variety of coal?

  1. Anthracite
  2. Peat
  3. Lignite
  4. BituminousAnswers. 1)Anthracite

Question 5.  Which of the following forms of energy is obtained from the Sun?

  1.  Wind energy
  2. Geothermal energy
  3. Chemical energy
  4. Solar energyAnswers. 4)Solar energy’ Short

Coal And Petroleum Science Answer Type Questions

A. What is petroleum?

Answers: Petroleum is a dark, oily liquid with a strong smell. It is a mixture of petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.

B. Why do we need to be judicious while using fossil fuels?

Answers: Fossil fuels are formed over millions of years and hence, if not used judiciously, they will run out soon. Also, burning of fossil fuels releases carbon dioxide and other gases, which are the main cause of air pollution.

UP Board Notes For Class 8 Science Chapter 6 Combustion And Flame Science

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Combustion And Flame Chapter In A Nutshell

  • Fuels of different varieties are used for various purposes in homes, industries, automobiles, etc.
  • Cowdung, wood, coal, charcoal, petrol, diesel, natural gas, L.P.G., etc., are various types of fuels.
  • Some fuels bum with a flame while some fuels do not give flame on burn ng.
  • Combustion is a chemical process in which a substance bums in the presence of oxygen to give off heat and light.
  • Fuels are combustible substances that may exist as solids, liquids or gases.
  • The presence of oxygen is essential for the process of combustion.
  • A combustible substance starts burning when it attains its ignition temperature.
  • Substances which have very high ignition temperature do not catch fire easily while substances like sodium and phosphorus which have low ignition temperature catch fire when exposed to air.
  • The ignition temperature of inflammable substances is very low. They catch fire rapidly and burn with fame.
  • Three important requirements essential to initiate a fire are the presence of oxygen, the Presence of a combustible substance arid heat supply to attain the ignition temperature of the combustible substance.
  • Fires can be controlled by – cutting off the supply of air bringing down the ignition temperature or removing the combustible substance.
  • Water is used to extinguish fire as it cools the combustible substance below its ignition temperature. In addition, the water vapours formed, surround the combustible substance and cut off the air supply. Water works as a fire extinguisher only when things like wood, paper, etc. catch fire.
  • The fire caused by to burning of oil or petrol cannot be controlled by water as water is heavier than oil. It settles down below the oil and oil continues to bum.
  • Water is not used in case of fires caused by electrical equipment as water is a good conductor of electricity and can thus cause electrocution.
  • Sand or carbon dioxide is used to control fires caused by the burning of liquid fuels or electricity.
  • Carbon dioxide is stored in cylinders in liquid form under high pressure.
  • Combustion can be classified as rapid combustion, spontaneous combustion and explosion.
  • The substances which vaporise on burning, give out flames. For example, kerosene oil.
  • The flame of a candle is divided into three zones – the innermost zone (dark zone), the middle zone (luminous zone) and the outermost zone (non-luminous zone).
  • The non-luminous zone is the hottest part of the flame.
  • The luminous zone of flame usually contains unburnt particles of carbon in it
  • A good fuel is readily available, cheap, bums easily in air, produces large amounts of heat and does not leave any unwanted substance behind.
  • The efficiency of a fuel is determined by its calorific value. The higher the calorific value of a fuel, the better the fuel.
  • The unit of calorific value is kilojoules per kg (KJ/kg).
  • Burning of fuels causes air pollution, health hazards, global warming, acid rain, etc.
  • Global warming results in the melting of polar glaciers which leads to a rise in the sea level. This may cause floods in the coastal areas.
  • Nitrogen and sulphur oxides are produced by the burning of fossil fuels. These oxides dissolve in rainwater to produce acid rain.
  • Acid rain is harmful to plants, buildings, statues, soil, etc.
  • CNG (Compressed Natural Gas) is a clean fuel as it causes no air pollution.

Read and Learn More UP Board Notes for Class 8 Science

Combustion And Flame Important Terms And Definitions

Combustible substances: The substances which bum easily in the presence of oxygen to give heat; and light are called combustible substances.
Non-combustible substances: The substances which do not bum in the presence of oxygen are
called non-combustible substances.
Ignition temperature: The minimum temperature at which a substance catches fire or starts burning; is called its ignition temperature.
Inflammable substances: Substances which have very low ignition temperature and quickly- catch fire are called inflammable substances.
Rapid combustion: The type of combustion in which a substance burns quickly to produce heat and light is known as rapid combustion.
Spontaneous combustion: The type of combustion in which a substance bursts into flames on its own is called spontaneous combustion.
Explosion: The type of combustion in which a substance bumps very rapidly with the evolution of tremendous amounts of heat, light and sound energy is called an explosion.
Flame: The gaseous light-emitting part of a fire is called a flame.
Calorific Value: The amount of heat energy released by the complete combustion of I kg of a fuel is: called its calorific value.
Global warming: Global warming is the slow rise in the temperature of the Earth’s atmosphere due to increased concentration of carbon dioxide.

Combustion

Combustion is a chemical process in which a substance burns in the presence of oxygen to give off heat and light. The minimum temperature at which a substance catches fire or starts burning is called its ignition temperature.
Inflammable substances like petrol, alcohol, and LPG (Liquefied Petroleum Gas) catch fire easily as these substances have very low ignition temperatures. Fires can be controlled by cutting off the air supply, removing the combustible substance, or bringing down the ignition temperature using fire extinguishers.
Combustion can be classified as rapid combustion, spontaneous combustion and explosion.

Combustion And Flame Activity 1

Aim: To identify combustible and non-combustible substances Procedure:
1. Take the materials given in the observation -.able.
2. Bum each of these materials one by one.
3. Note down the observations in the observation table.

Observation:

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustible And Non Combustible products

Conclusion: Wood, paper, kerosene oil, straw, charcoal, and matchsticks are combustible substances while iron nails, stone pieces, and glass are non-combustible substances.

Combustion And Flame Activity 2

Aim: To investigate the conditions necessary for combustion Procedure:
1. Case (a) Fix a candle on a table and put a glass chimney over it
2. Rest the candle on a few wooden blocks such that air can enter the chimney.
3. Observe the flame of the candle.
4. Case (b) – Remove the wooden block and ‘est the chimney on the table.
5. Observe the flame of the candle again.
6. Case (c) – Put a glass plate over the chimney and observe the flame.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion and Flame Activity 2

Experiment to show that air is necessary for burning

Observation:

1. The candle burns freely in case (a) when air can enter the chimney from below.
2. The flame of the candle flickers and produces smoke in case (b) when air does not enter the chimney from below.
3. The flame of the candle goes off in case (c) when air is not available.

Conclusion: Air is necessary for the process of combustion to take place

Combustion And Flame Activity 3

Aim: To show that combustion takes place in the presence of air
Procedure:
1. Place a piece of burning wood or charcoal on an iron plate or tawa.
2. Cover it with a glass jar or tumbler, or a transparent plastic jar.
3. Observe the burning wood or charcoal.

Observation: The wood or charcoal stops burning after some time.
Conclusion: Air is necessary for the process of combustion to take place.

Combustion And Flame Activity 4

Aim: To show that a substance starts burning at its ignition temperature
Procedure:

1. Make two paper cups from paper.
2. Pour about 50 ml of water in one of the cups.
3. Carefully, heat both the cups separately with a candle and observe them.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion And Flame Activity 4

heating paper cups

Observation:

1. The temperature of the empty paper cup reaches its ignition temperature and starts burning.
2. The heat supplied to the paper cup filled with water is transferred to water by conduction. Thus, in the presence of water, the ignition temperature of paper is not reached and it does not burn.
Conclusion: A substance catches fire at its ignition temperature.

Combustion And Flame Objective-Type Questions

A. State whether the following statements are true or false.

1. Substances which burn easily are called non-combustible substances.
2. Water can be used to extinguish fires caused by to burning of { kerosene oil.
3. A good fuel should be safe to handle.
4 All fuels have the same ignition temperature.

Answers: 1. False 2. False 3. True 4. False

B. Answer the following in one word.

1. Name a gas which is a supporter of combustion.
2. Give an example of an inflammable substance.
3. Which type of combustion produces a tremendous amount of heat, light and sound energy?

Answers: 1. Oxygen 2. Kerosene oil 3. explosion

Combustion And Flame Long Answer Type Questions

A. What are the different types of combustion? Give an example of each.

Answers. The different types of combustion are rapid combustion, spontaneous combustion and explosion. Example of rapid combustion – When a burning matchstick is brought near a gas burner, the gas starts burning immediately with the evolution of heat and light
Example of spontaneous combustion – Sodium and phosphorus bums spontaneously when exposed to air. Example of an explosion – When crackers are ignited, heat, sound and light energy are produced.

Flame

Answers. The substances which vaporise during burning, give out flames. For example, when we bum a candle wick, the wax around it melts and vaporises upward through the wick. These vapours bum in the air and; produce a flame.
The flame of a candle is divided into three zones – the innermost zone (dark zone), the middle; zone (luminous zone) and the outermost zone (non-luminous zone). No combustion takes place! the innermost zone of the flame while complete combustion takes place in the outermost zone of the flame.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion And Flame

different zones of a candle flame

Combustion And Flame Activity 5(a)

Aim: To show that substances that vaporise during burning, give flame Procedure:
1. Light a candle.
2. Hold a glass tube with a pair of tongs and introduce its one end in the dark zone of a non-flickering candle flame.
3. Bring a burning matchstick near the other end of the glass tube.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion And Flame Activity 5a

Observation: The molten wax of the candle rises through the wick and vaporises which gives a flame near the other end of the glass tube.
Conclusion: Substances that vaporise during burning, give flame.

Combustion And Flame Activity 5(b)

Aim: To show that unbumt carbon particles are present in the luminous zone of the flame Procedure:
1. Light a candle.
2. Hold a clean glass plate or a glass slide into *. he luminous zone of the flame for 10 minutes.
3. Remove the glass plate and observe it.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion And Flame Activity 5(b)

Observation: A blackish ring is formed on the glass plate or slide.
Conclusion: Unbumt carbon particles are present in the luminous zone of the flame.

Combustion And Flame Activity 5(c)

Aim: To show that the non-luminous zone is the hottest part of the flame. Procedure:
1. Light a candle.
2. Hold a clean thin long copper wire inside the flame for some time.
3. Observe the copper wire just outside the flame.

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Combustion And Flame Activity 5(c)

Observation: The copper wire just outside the flame becomes red-hot
Conclusion: The non-luminous zone is the hottest part of the flame.

Combustion And Flame Objective-Type Questions

A. State whether the following statements are true or false.

  1.  Kerosene oil vaporises while burning.
  2. A substance which does not vaporise during burning gives flame.
  3.  Camphor bums with a flame.

Answers: 1. True 2. False 3. True

B. Fill in the blanks.

  1. _____ zone is the hottest part of the flame.
  2. The innermost zone of a flame is also known as______zone.
  3. ____ zone of the flame contains unbumt carbon particles.

Answers: 1. Non-luminous 2. Dark 3. Luminous

Combustion And Flame Short Answer Type Questions

A. Why middle zone of a flame is yellowish in colour?

Answers. Partial combustion of the combustible substance takes place in the middle zone of a flame due to an insufficient supply of oxygen in this region. The middle zone consists of unburnt carbon particles which become red hot and impart a yellow colour to the flame.

Fuels

Answers. Fuels are the substances which burn to produce heat and light energy. The efficiency of a fuel is determined by its calorific value. The higher the calorific value of a fuel, the better the fuel. Hydrogen has the highest calorific value.
Burning of carbon-containing fuels like wood, coal, etc. releases unburnt carbon particles into the environment Incomplete combustion of carbon-containing *fuels like petrol, kerosene, etc. produces carbon monoxide. Burning of coal in factories and power plants produces gases like sulphur dioxide and nitrogen dioxide. Carbon-containing fuels also release carbon dioxide which is a greenhouse gas and causes global warming.

Combustion And Flame Objective-Type Questions

A. State whether the following statements are true or false.

Acid rain is harmful to plants, buildings, statues, soil, etc.

  1. CNG produces a high amount of pollutants.
  2.  A good fuel should have low calorific value.

Answers: 1. True 2. False 3. False

B. Fill in the blanks.

  1. Fuels burn to produce_____and energy.
  2. Incomplete combustion of carbon-containing fuels produces______ gas.
  3. _____ results in the melting of polar glaciers.

Answers: 1. Heat, light 2. Carbon monoxide 3. Global warming

Combustion And Flame Long Answer Type Questions

A. List the harmful effects of burning carbon-containing fuels.

Answers.

Some of the harmful effects of burning carbon-containing fuels are:
1. Burning of fuels like wood, coal, etc. releases unburnt carbon particles which cause respiratory problems such as asthma and bronchitis.
2 Incomplete combustion of fuels like petrol, kerosene, etc. produces carbon monoxide which is a highly poisonous gas. If a person is exposed to carbon monoxide for a long time, it may prove fatal and he may even die.
3. Burning of coal in factories and power plants produces gases like sulphur dioxide and nitrogen d oxide which dissolve in rainwater to form acid rain.
4. Carbon-containing fuels also release carbon dioxide which can trap heat. This increases the temperature of the atmosphere and causes global warming.

Combustion And Flame Textbook Exercises

Question 1. List the conditions under which combustion can take place.

Answers.

The three important requirements for combustion to take place are:

  1. The presence of a supporter of combustion live, oxygen
  2. Presence of a combustible substance
  3. Heat supply to attain the ignition temperature of the combustible substance

Question 2. Fill in the blanks:

  1. Burning of wood and coal causes_______ of air.
  2. A liquid fuel, used in homes is______.
  3. Fuel must be heated to its______ ______ before it starts burning
  4. The fire produced by oil cannot be controlled by——

Answers:

  1. Pollution
  2. Kerosene oil before it starts burning
  3. Ignition temperature
  4. (Water

Question 3. Explain how the use of CNG in automobiles has reduced pollution in our cities.

Answers. CNG (Compressed Natural Gas) is a clean gaseous fuel. It has a high calorific value. It burns completely in the air and does not produce any harmful gases. It does not leave any residue after burning. So, pollution is reduced by the use of CNG in automobiles in our cities. of air.

Question 4. Compare LPG and wood as fuels. 

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Compare LPG and wood as fuels.

Question 5. Give reasons:

1)Water is not used to control fires involving electrical equipment
2)LPG is a better domestic fuel than wood.
3)Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not

Answers.

(1) Water is not used to control fires involving electrical equipment because water is a good conductor of electricity. Thus, it can cause electrocution.
(2) LPG is a better domestic fuel than wood because it is a cleaner fuel than wood. It neither produces smoke nor does it leave any residue after burning. It has a high calorific value. While wood produces a lot of smoke on burning and leaves behind ashes on burning. Wood has a low calorific value.
(3) When paper wrapped around an aluminium pipe is brought near a flame, it does not bum because the heat given to the paper gets transferred to the aluminium pipe and the ignition temperature of the paper is not attained.

Question 6. Different Zones of a Candle Flame

UP Board Notes for Class 8 Science Chapter 5 Combustion And Flame Science Different Zones of a Candle Flame

different zones of a candle flame

Question 7. Name the unit in which the calorific value of a fuel is expressed.

Answers. The unit in which the calorific value of a fuel is expressed in kilojoules per kilogram (KJ/kg).

Question 8. Explain how C02 can control fires.

Answers. Carbon dioxide is heavier than oxygen and covers the combustible substance like a blanket Thus, carbon dioxide cuts off the contact between the combustible substance and air. This extinguishes the fire.

Question 9. It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.

Answers. Green leaves have a lot of moisture in them which increases their ignition temperature. The dr)’ leaves do not contain moisture arid thus, their ignition temperature is low. Therefore, a heap of green leaves do not bum easily but the dr)’ leaves catch fire easily.

Question 10. Which zone of a flame does a goldsmith use for melting gold and silver and why?

Answers. Goldsmiths usually use the outermost layer.e., the non-luminous zone of the flame for melting gold and silver because it is the hottest part of the flame.

Question 11. In an experiment, 4.5 kg of fuel was completely burnt. The heat produced was measured to be 180,000 KJ. Calculate the calorific value of the fuel.

Answers. Mass of the fuel = 4.5 <g Heat produced = 180,000 KJ
We know the calorific value = Heat produced by burning I kg of the fuel
Therefore, Calorific value = _ 4Q(000 kl/kg
4.5 kg

Question 12. Can the process of rusting be called combustion? Discuss.

Answers. Yes, the process of rusting can be called combustion.
Combustion is a chemical process in which a substance reacts with oxygen and gives off heat and light Rusting of iron is also a chemical process in which iron reacts with oxygen at a very slow rate and gives off heat. So, rusting can be termed as a slow combustion process.

Question 13. Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?

Answers. Ramesh’s beaker will get heated in a shorter time because the outermost part of the flame is the hottest.

Combustion and Flame Hots corner

A. Why a person should not run when his clothes are on fire?

Answers. A person, whose clothes are on fire, should not run because running provides more oxygen to the flames. As oxygen is a supporter of combustion, this will increase the fire and cause more burns to the person.

B. Why is a matchstick lighted by rubbing it on the rough surface provided on the side of the matchbox?

Answers. When we rub a match stick on the rough surface of the matchbox, it produces heat due to friction. This heat raises the temperature of the chemical present on the matchstick head to its ignition temperature. Therefore, the chemical substance catches fire and the matchstick starts burning.

Combustion And Flame Practice Exercises

A. Encircle the correct option in the following sentences:

1. Hydrogen/LPG has the highest calorific value.
2. Not much air is available in the innermost zone/middle zone of a candle flame.
3. The higher/Lower the calorific value of a fuel, the better the fuel.
4. A good fuel should be cheap/expensive.
5. The outermost zone of a candle flame is the coolest/hottest

Answers: 1. Hydrogen 2. Middle zone 3. Higher 4. Cheap 5. Hottest

B. Fill in the blanks.

1. Materials such as glass, metals, ceramics, etc., are known as
2. The outermost zone of a flame is known as
3. A clean fuel does not produce
4. The gaseous light-emitting part of a fire is called

Answers: 1. Non-combustible while burning. 2. Non-luminous zone 3. Smoke materials. 4. Flame

Combustion And Flame Short Answer Type Questions

Question 1. Why water cannot be used to put off fires caused by oil?

Answers. Water cannot be used to put off fires caused by the oil because:
A)oil is lighter than water and keeps floating on it. Thus, the fire keeps on burning.

Question 2. Why is it dangerous to burn coal in a closed room? It is dangerous to burn coal in a closed room because:

Answers.

1) Burning of coal releases unburnt carbon particles into the environment. These are very fine particles that can cause respiratory problems such as asthma and bronchitis.
2) Incomplete combustion of coal produces carbon monoxide which is a highly poisonous gas. If a person is exposed to carbon monoxide for a long time, it may prove fatal and he may even die.

Question 3. How is a flame produced when a candle wick is burnt?

Answers. When a candle wick is burnt, the wax around it melts and vaporises. The vaporised molten wax moves upward through the wick. These vapours burn in the air and produce a flame.

UP Board Notes for Class 8 Science

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Chapter Wise UP Board Notes for Class 8 Biology Pdf free download was designed by expert teachers from latest edition of UP Board books to get good marks in board exams. UP Board Class 8 Biology Notes contains Textbook Readers and Supplementary Readers of all chapters are part of Revision Notes for grade 8 Biology. Here we have given notes Class VIII.

UP Board Notes for Class 8 Science

UP Board Notes for Class 8 Science Chapter 1 Crop Production and Management

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Crop Production And Management Concepts

  • Types of Crops
  • Basic Practices of Crop Production
  • Food from Animals

Chapter In A Nutshell

  • The process of growing, cultivating, and harvesting crops is known as agriculture.
  • Plants of the same kind that are cultivated in fields on a large scale for food, clothing or commercial purposes are known as crops.
  • Several crops like rice, wheat, maize, cotton, vegetables, etc., are grown on a large scale for food, clothing, and commercial purposes.
  • On the basis of the season in which they grow, crops grown in India are classified into Kharif and rabi crops.
  • Kharif crops are planted in the rainy season and harvested in October. A few examples of Kharif crops are paddy, maize, cotton, etc.
  • Rabi crops are planted in the winter season and harvested in March or April. A few examples of rabi crops are wheat, mustard, pea, gram, etc.
  • For growing crops, farmers perform several activities known as agricultural practices. They include:
  • Preparing the soil: It involves plowing, leveling, and applying fertilizers. Plowing is the process of loosening and turning the soil with a plow, hoe, etc. A wooden leveler is used for pressing the soil and fertilisers or manures are then applied to the soil.
  • Selection of good quality seeds: Good quality seeds are clean and healthy seeds of a good variety.
  • Sowing of seeds: Planting seeds into the soil is called sowing. Seeds can be sown by broadcasting or scattering: using seed drills or by transplantation. In transplantation, seeds are sown in a nursery. Small plants that grow out of these seeds are transferred to the fields.
  • Adding manures and fertilizers to the soil: Manures are organic substances obtained by the decomposition of dead plants and animal wastes. Manures are not nutrient specific. Besides adding nutrients to the soil, manures also improve the texture of the soil and add beneficial soil
  • organisms to the soil. Fertilisers are chemicals, which increase the fertility of soil by providing specific nutrients to the soil. Examples of fertilizers are urea, ammonium phosphate, NPK (nitrogen, phosphorous, and potassium), etc.
  • Irrigation: It is the artificial supply of water to the soil at regular intervals and in a regular quantity as per the need of the crop. It can be done by traditional or modem methods. Traditional methods of irrigation include canal irrigation, furrow irrigation, chain pumps, etc.
    They are cheaper but often lead to a waste of water. Sprinkler irrigation and drip irrigation are j modem methods of irrigation and help in saving water.
  • Weeding: Weeds are unwanted plants, which grow along the main crops and compete with them for sunlight nutrients, water, and space. Removal of unwanted plants from a field is called weeding. It can be done manually with a hoe or by using chemicals known as weedicides.
  • Harvesting: Cutting and gathering of crops upon maturity is called harvesting. It is done manually; using a sickle or with the help of a machine called a harvester.
  • Threshing: Harvested crops are separated from the plant bulk by beating the bulk on floors or with the help of machines. This process is called threshing.
  • Winnowing: Grains are separated from the chaff by a process called winnowing.
  • Storage: Harvested and cleaned grain must be stored in a safe and dry place. Stored grain may; be sprayed with pesticides to keep away pests. The grain is usually stored in jute bags or metallic; bins.
  • Large-scale storage of go-as is done in silos and granaries.
  • With the increase in population, several techniques are used for increase ng crop yield.
  • Mixed cultivation and crop rotation is used so that the nutritional needs of one crop are fulfilled by another crop.
  • Atmospheric nitrogen is fixed into the soil by nitrogen-fixing bacteria called Rhizobium, which is present in the root nodules of leguminous plants.
  • The nitrogen cycle is the process of the circulation of nitrogen between the soil, organisms, and the atmosphere.
  • Rearing of animals on a large scale for products such as milk, meat, eggs, fiber, hide, honey, etc., is known as animal husbandry.

Read and Learn More UP Board Notes for Class 8 Science

Types of Crops

  • Until around 10,000 BC, human beings were nomads and went from one place to another in search of food. They ate raw fruits, vegetables, and meat of animals. It was much later that is culture was discovered and human beings started to grow ing crops. Crops can be classified in many different ways. Based on the type of food they provide, crops can be classified as cereals, fruits, vegetables, oilseeds and nuts, legumes, sugar crops, etc. Crops can also be classified on the basis of the season in which they grow. Crops grown in India are classified as Kharif and rabi crops. Kharif crops are planted in the rainy season and harvested in October. A few examples of Kharif crops are paddy, maize, cotton, etc. Rabi crops are planted in winter and harvested in March or April. A few examples of rabi crops are wheat, mustard, pea, gram, etc. Pulses and vegetables are generally grown in summer.

Crop Production And Management Objective Type Questions

A. State whether the following statements are true or false.

  1. Wheat is a rabi crop.
  2. Crops can be categorized on the basis of the type of food they provide.
  3. Gram is a Kharif crop.

Answers

  1. True
  2. True
  3. False

B. Multiple Choice Questions.

1. In which category of crops would you place wheat and rice?

a) Rabi crops
b) Kharif crops
c) Fruits
d) Cereals

2. Which of the following is a Khar/From?

a) Linseed
b) Mustard
c) Groundnut
d) Pea

3. Which of following constitutes the food that early human beings ate?

a) Cereals
b) Raw fruits, vegetables, and meat
c) Milk products
d) None of these

4. Under which of the following type of crops would you categorise mustard?

a) Cereals
b) Fruits and vegetables
c) Oilseeds and nuts
d) Sugar crops

Answers

  1. (d) Cereals
  2. (c) Groundnut
  3. (b) Raw fruits, vegetables, and meal
  4. (c) Oilseeds and nuts

C. Fill in the blanks.

1. ___________crops are planted in winter and _________in March or April.
2. _______and are __________grown in summer.

Answers

  1. Rabi, harvested
  2. Pulses, Vegetables

Coproduction And Management Short Answer Type Questions

Question 1. Define rabi and Kharif crops with two examples of each.

Answer
 Crops which are grown in the winter season and harvested in March or April are known as rabi crops. Examples of rabi crops are wheat and mustard. Crops which are grown in the rainy season and harvested in October are known as Kharif crops Examples of Kharif crops are paddy and cotton.

Question 2. Define agriculture.

Answer
The process of growing, cultivating, and harvesting crops is known as agriculture.

Question 3. What is staple food?

Answer
The food which forms the main part of our diet is called staple food, e.g. rice and wheat. They are grown on a large scale in vast fields as they are consumed in large amounts.

Basic Practices Of Crop Production

Farmers perform several activities for producing crops and these are known as agricultural practices. The basic steps of growing crops include the following step:

  1. Soil preparation which includes plowing, leveling, and applying fertilisers. Plowing is the process of loosening and turning soil using a plow, hoe, etc. Soil is loosened and overturned to make it better ventilated and suitable for the growth of tiny organisms living in it. During dry season, Dloughing turns soil into big mud pieces or crumbs, which are broken down by a park. At times, a wooden leveler is used for pressing the soil
  2. The process of planting seeds in the soil is called sowing. Before sowing good quality seeds must be selected. Seeds can be sown in fields by hand (broadcasting) or with the help of a seed drill.
  3. Manure or art facial fertilisers are added to the soil to provide nutrients for the healthy growth of crops.
  4. Water is supplied to the soil at regular intervals and n regular quantity. This is called inigation and it can be done by traditional or modem methods. Traditional methods of irrigation include canal irrigation, furrow irrigation, chain pumps, etc. They are cheaper but often lead to a waste of water. Sprinklers and drip irrigation are modem methods of irrigation and help in saving water.
  5. Unwanted plants are removed from fields either manually or by using chemicals called weedicides. Examples of weedicides are linazine, dilation, etc.
  6. Cutting and gathering of crops upon maturity is called harvesting. It is done manually using a sickle or with the help of a machine called a harvester.
  7. Grains are obtained from the harvested crops by threshing and winnowing.
  8. Threshing: Separation of grains from the plant bulk is called threshing. On a large scale, threshing is done using animals. In large farms, a machine called a combine harvester is used for both harvesting and threshing.
  9. Harvested grains are stored in a safe and dry place before they are made available for consumption. Pesticides may be sprayed to keep away pests from stored grains. Grains are usually stored in jute bags or metallic bins. Large-scale storage of grains is done in silos and granaries. Grains stored at home can be protected from pests by putting dried Neem leaves in them.

Crop Production and Management Activity 1

Aim: To show that damaged seeds would float on top of water Procedure:

  1. Take a beaker and fill half of it with water.
  2. Put a handful of wheat seeds into it and stir well.
  3. Leave the beaker undisturbed for a few minutes.

Observation: Few seeds float on top of the water.
Conclusion: Damaged seeds are hollow from inside and thus, they float on top of water.

Crop Production and Management Activity 2

Aim: To show that manure or fertilisers are needed for good growth of crops
Procedure:

  1. Germinate moong or gram seeds in three equal-sized containers.
  2. In the first container, sow the seeds into the soil.
  3. In the second container, add some cow dung to the soil.
  4. In the third container, add urea to the soil.
  5. Keep the three containers in a warm place and water them every day.
  6. Observe after 7 to 10 days.

Observation: Growth of seeds in the second and the third container is better than in the first one. Conclusion: Manures and fertilisers help the seeds to grow- better.

Objective Type Questions

A. State whether the following statements are true or false.

  1. Soil preparation involves plowing, leveling, and applying fertilizers.
  2. Water should be supplied to crops only when the soil seems dry and not at regular intervals
  3. Tilled and plowed soil is better aerated and lets water and nutrients reach to the roots of the plants.
  4. Weeds are unwanted plants, which grow alongside crops and must be removed for healthy growth of crops.
  5. Cutting and gathering of crops upon maturity is called threshing.
  6. A combined harvester is used for both harvesting and threshing.
  7. Leguminous plants bear root nodules.
  8. Winter crops are known as Kharif crops.
  9. In India, special festivals are held commemorating the harvest.
  10. Large-scale storage of grains is done in silos or granaries.

Answer

  1. True
  2. False
  3. True
  4. True
  5. False
  6. True
  7. True
  8. False
  9. True
  10. True

Crop Production and Management Multiple Choice Questions.

1. In which category of crops would you place cotton?

a) Rabi crops
b) Kharif crops
c) Fruits
Cereals

2. Which of the following is a manual method of sowing seeds directly into the field?

a) Using seed drills
b) Broadcasting
c) Transplantation
d) None of these

3. Which of the following is a result of adding fertilizers to the soil?

a) Addition of specific nutrients to the soil
b) Improvement of soil texture
c) Addition soil organisms to the soil
d) None of these

4. Which of the following can be used for protecting stored grains at home?

a) Weedicides
b) Dried Neem Leaves
c) Dried Tulsi Leaves
d) None of these

Answers

  1. (b) Kharif crops
  2. (a) Addition of specific nutrients to the soil
  3. (b) Broadcasting
  4. (b) Dried Neem Leaves

Fill in the blanks.

  1. A ______________may be used for sowing seeds
  2. ________and______ irrigation are modern methods of irrigation.
  3. A___________is used for harvesting crops.
  4. ____________ are chemicals that kill or destroy weeds.
  5. When crops in a field are supplied water at regular intervals of time, it is called_______
  6. __________of crops take place due to lack of water.
  7. The area of land on which crops are grown is known as a________
  8. The downward movement of water through the pores of the soil is known as________
  9. There are two types of fertilizers: and, artificial.
  10. Rhizobium bacteria fixes__________into the so

Answers

  1. Seed drill
  2. Sprinkler and drip
  3. Sickle
  4. Weedicides
  5. Irrigation
  6. Shriveling
  7. Crop field
  8.  Percolation
  9. Natural
  10.  Atmospheric nitrogen

Crop Production and Management Short Answer Type Questions

Question 1. Before sowing seeds, soil is plowed and tilled. Why?

Answer Soil is plowed and tilled to aerate and loosen it up. This allows water to percolate down the layers of soil and reach to the roots of plants. Aeration of soil helps roots to grow and breathe. It also aids in the growth of worms and microbes in the soil. Worms and microbes make the soil fertile.

Question 2. What are the different methods of sowing seeds?

Answer Seeds can be sown into the soil using broadcasting, seed drills, or by transplanting. In broadcasting, seeds are broadcasted or scattered over the plowed soil by hand. A seed drill is a small device that sows seeds at equal distances. In transplantation, seeds are sown in nursery beds and once they grow into young plants, they are uprooted and planted in the field.

Question 3. What are the basic requirements for growing any crop?

Answer
The basic requirements for growing a crop are:

  1. A proper type of soil as per the need of the crop
  2. Sowing good quality, healthy seeds at the right time
  3. Use of manures or fertilizers
  4. Regular irrigation
  5. Proper weeding
  6. Protection from pests
  7. Harvesting at the right time

Food from Animals

  • Animals provide us with many useful products such as milk, eggs, meat, fibers, hide, honey, etc. These animals need to be provided with food, shelter, and care. Rearing of animals on a large scale for food, clothes or other products is known as animal husbandry. Besides providing these products, animals help us in various tasks. Such animals are called draught animals. Examples of draught animals are horses, ox, etc.

Crop Production And Management Activity 3 Objective Type Questions

State whether the following statements are true or false.

  1. Rearing of honeybees on a large scale is known as apiculture.
  2. We get hide and meat from poultry birds.
  3. Animals such as goats and sheep provide us with fibers.
  4. Cows and buffaloes provide us with milk.
  5. Honey is obtained from cows.

Answers:

  1. True
  2. False
  3. True.
  4. True
  5. False

Multiple Choice Questions.

Question 1. ‘What is rearing of silkworms for producing silk called?

  1. Pisciculture
  2. Sericulture
  3. Apiculture
  4. None of these

Question 2. Which of the following products is provided by cows and buffaloes?

  1. Milk
  2. Hide
  3. Fuel
  4. All of these

Question 3. ‘What is the name of the process in which seeds or grains are separated from the plant bulk Dy beating it on a hard floor?

  1. Winnowing
  2. Broadcasting
  3. Threshing
  4. Weeding

Question 4. ‘Which of the following is used for removing weeds?

  1. Weedicides
  2. Pesticides
  3. Fertilizers
  4. Manures

Question 5. ‘Which of the following is a traditional method of irrigation?

  1. Canal irrigation
  2. Furrow irrigation
  3. Chain pumps
  4. All of these

Question 6. Which of the following is provided to us by animals?

  1. Wood
  2. Rubber
  3. Wheat
  4. Wool

Question 7. ‘What is the name given to crops which are mainly grown for money?

  1. Food crops
  2. Cash crops
  3. Vegetables
  4. Oilseeds and nuts

Question 8. What do animals get from crops?

  1. Fodder
  2. Oilcake
  3. Grains
  4. All of these

Answers:

  1. (2) Sericulture
  2. (4) All of these
  3. (3) Threshing
  4. (1) Weedicides
  5. (4) All of these
  6. (4) Wool
  7. (2) Cash crops
  8. (4) All of these

Fill In the blanks.

  1. _____ and ______are milk yielding animals.
  2. ____ are provided by a hen.

Answers:

  1. Buffalo, cow
  2. Eggs

Crop Production and Management Short Answer Type Questions

Question 1. Explain how soil gets affected by the continuous plantation of the same plant. How can this be prevented?
Answer
 By repeated growth of the same plant, specific nutrients get depleted from the soil. To prevent this, different types of crops are grown in succession and this practice is known as crop rotation.

Exercises

Question 1. Select the correct word from the following list and fill in the blanks:

float, water, crops, nutrients, preparation

  1. The same kind of plants grown and cultivated on a large scale at a place are called
  2. The first step before growing crops is the of soil.
  3. Damaged seeds would on top of water.
  4. For growing of crops, sufficient sunlight from the soil are essential.

Answers:

  1. Crop
  2. Preparation
  3. Float
  4. Water, nutrients

Question 2. Give two examples of each.

  1. Kharif crop
  2. Rabi crop

Answers:

  1. Paddy and Maize
  2. Wheat and Gram

Question 3. Write a paragraph in your own words on each of the following.

Answer

  • Preparation of soil
  •  Sowing
  • Weeding
  • Threshing
  • Preparation of soil: Soil is loosened and overturned to make it better ventilated and suitable for the growth of tiny organisms living in it. The ent reprocess is called ’tillage and plowing’. During dry season, plowing turns the soil into big mud pieces or crumbs, which are then broken down with a plank. The plowed soil is liable to be removed by wind and water. Therefore, a wooden leveler is used for pressing the soil.
  • Sowing: The process of planting seeds into the soil is called sowing. It is the most important part of crop production. Before sowing, good-quality seeds must be selected. Seeds can be sown in fields by hand (broadcasting) or with the help of i seed drill.
  • Weeding: It is a process of the removal of unwanted plants, i.e., weeds from fields. It is necessary to remove weeds as they compete with the main crop for water, nutrients, sunlight, etc. Weeds may be removed manually by uprooting or cutting or by using chemicals called weedicides. Examples of weedicides are linazine, dilation, etc. The best time to remove weeds is before they produce flowers and seeds. Hand removal of weeds can be done with burps or a tractor-driven harrow.
  • Threshing: Separation of grains from the bulk of harvested plants is called threshing. Animals are used on a large scale for threshing. In large ”arms, a machine, a combined harvester, is used for both harvesting and threshing.

Question 4. Explain how fertilisers are different from manure.

Answer
Fertiliser Manure
a) These are chemical compounds rich in nitrogen, phosphorus, and potassium. a) These are organic substances prepared from the decomposition of plants and animal wastes.
b) They are man-made and manufactured on a large scale in factories. b) They are made by natural processes either on a small or large scale.
c) Chemical fertilisers are nutrient specific, i.e., nitrogenous, phosphatic, etc. c) They contain a mixture of various nutrients recycled from biomass wastes.

Question 5. What is irrigation? Describe two methods of irrigation which conserve water.

Answer
Applying water to the soil at regular intervals of time and in regular quantity is called irrigation. The time and frequency of irrigation vary from crop to crop, soil to soil, and season to season. The latest irrigation methods that help in conserving water are:

  • Sprinkler system: This system is very useful on uneven land or on sandy soil. The pipes of the sprinkler system have rotating nozzles and are joined to the main pipeline at regular intervals. Water comes out from the rotating nozzles and is sprinkled on the crops as if it raining.
  • Drip system: In this system, water is added drop by drop to the soil just at the position of the roots. Water wastage is minimised and that is why the drip system is a boon for regions where availability of water is limited.

Question 6. If wheat is sown in the Kharif season, what would happen? Discuss.

Answer
Wheat is a rabi crop, i.e., it is grown in the winter season If it is sown in the Kharif season, it will get more water, which is harmful to the crop. The wheat crop will neither be healthy nor will it provide a good yield.

Question 7. Explain how soil gets affected by the continuous plantation of crops in a field.

Answer
For better growth of crops, fertilisers are added regularly to a field. Fertilisers are nutrients like nitrogen, phosphorus, potassium, etc. Using them year after may change the nature of the soil. The soil may become too alkaline or acidic and less fertile.

Question 8. What are weeds? How can we control them?

Answer
Weeds are undesirable plants that grow naturally along with the crops. Removal of weeds is called weeding. The following methods can be used to control weeds:

  • Tilling: The process of loosening and turning of the soil is called till ng or plowing. This is done by using a plow. Tilling uproots and kills weeds.
  • Manual removal: This method includes physical removal of weeds by uprooting or cutting them close to the ground. This is done with the help of a khurpi or harrow.
  • Chemical method: In this method, weeds are controlled or killed by using chemicals called weedicides. They are sprayed in fields with a sprayer.

Question 9. Arrange the following boxes in the proper order to make a flow chart of sugarcane crop production.
Answer:

UP Board Notes for Class 8 Science Chapter 1 Crop Production And Management a flow chart of sugarcane crop production.

Question 10. Complete the following word puzzle with the help of the clues given below.
Answer:

UP Board Notes for Class 8 Science Chapter 1 Crop Production And Management Word Puzzule

Down
1. Providing water to the crops
2. Keeping crop grains for a long time under proper
5. Certain plants of the same kind that are grown on a large scale Across

Across
3. A machine used for cutting matured crop
4. A rabi crop that is also one of the pulses
6. A process of separating grains from chaff

Answers

Down
1. Irrigation
2. Storage
5. Crop

Across
3. Harvestor
4. Grams
6. WINNOWING

Crop Production and Management Hots Corner

Question 1. Which irrigation method would you recommend for a region in Rajasthan? Why?
Answer: Rajasthan is a dry region and hardly gets any rain. The soil found there is sandy and has very poor water-holding capacity. Hence, modem methods of irrigation like drip irrigation and sprinkler irrigation should be used to water crops in such regions.

Question 2. The following table shows the yield of wheat crops grown by Ram Singh between the years 2005 and 2010. Look at the table below and answer the questions that follow.
Answer:

UP Board Notes for Class 8 Science Chapter 1 Crop Production And Management Ram Singh Between The Years 2005 And 2010

1. What could be the reason for a decrease in the yield of wheat crops in the year 2007?

Answer
Growing the same crop in the same field year after year decreases the fertility of soil. The soil gets depleted of nutrients. Hence, the yield of wheat crops in the year 2007 is low.

2. What could be the reason for all increase in die yield of wheat crops in the year 2009?

Answer
Peas are leguminous plants. Rhizobium bacteria present in the root nodules of leguminous plants fix atmospheric nitrogen into the soil. This probably increased the fertility of the soil and resulted in an increase in the yield of wheat crops in the year 2009.

Question 3. A farmer grew seeds in his field but only a small number of plants germinated. The field was plowed, tilled, leveled, and manured properly. He also irrigated the soil regularly and took care of weeds, pests, and insects. What do you think is the reason behind the poor germination of seeds?

Answer
The reason behind it might be unhealthy seeds. Everything else has been taken care of and hence, this is the only possible reason for poor germination of seeds.

Question 4. In a musk melon field, it was observed that a few fruits would sometimes crack. What do you think is the reason behind it?

Answer
Fruits in a field would sometimes crack due to excess absorption of water. This may happen due to improper drainage or leveling of the field.

Crop Production and Management Practice Exercise

Objective Type Questions

A. Circle the odd one out.

  1. Wheat, rice, maize, mango, millet
  2. Sugarcane, jute, cotton, flax, coconut
  3. ‘Wheat, mustard, gram, soybeans, linseed
  4.  Plowing, tilling, harvesting, leveling, manuring
  5. Eggs, silk, paper, wool, honey

Answers:

  1. Mango
  2. Sugarcane
  3. Soybeans
  4. Harvesting
  5. Paper

B. Give one word for the following.

  1. Nitrogen-deficient soil can be made nitrogen-rich by applying this farming practice
  2. Chemicals that are used for killing pests
  3. The process by which seeds are scattered in the field by hand
  4. Nitrogen-fixing bacteria, Rhizobium, lives in the root nodules of these plants
  5. Rearing of fish on a scale

Answers:

  1. Crop rotation
  2. Pesticides
  3. Broadcasting
  4. Legumes
  5. Pisciculture

C. State whether the following statements are true or false.

  1. The process of cutting and gathering crops is called harvesting.
  2. Paddy is a rabi crop.
  3. Tea is a leguminous crop.
  4. The microorganisms found in the roots of leguminous plants are Rhizobium bacteria.

Answers:

  1. True
  2. True
  3. False
  4. False

Crop Production and Management Short Answer Type Questions

Question 1. What are weeds?

Answer
Weeds are unwanted plants that grow alongside crops and compete with crops for food, water, and sunlight. By taking up nutrients, space, water, and sunlight; weeds adversely affect crop yield and hence, should be removed as soon as possible.

Question 2. What is poultry farming?

Answer
The rearing and breeding of chickens and hens on a large scale is called poultry farming. It is done to produce eggs and meat

Question 3. What is crop rotation? What are its advantages?

Answer

Growing the same type of crop on the same land, again and again, depletes the soil of nutrients, deteriorates soil quality, and leads to poor crop yield. Growing crops of different kinds in succession is termed crop rotation. It helps maintain the quality of the soil.
Let us consider the case of nitrogen-fixing bacteria. These are found in the roots of leguminous plants. Nitrogen-fixing bacteria help in fixing atmospheric nitrogen in the soil. Planting legumes and Plants in the soil will result in recovering nitrogen in the soil and increase its fertility. A sample four-year crop rotation plan may be as follows:

Leaf crop —> Fruit crop —> Root crop —> Leguminous crop

Also Read

UP Board Notes for Class 8 Science Chapter 2 Microorganisms: Friend and Foe

by

Microorganisms: Friend and Foe Concepts

  1. Types of Microorganisms
  2. Useful Microorganisms
  3. Harmful Microorganisms
  4. Nitrogen Fixation

Chapter In A Nutshell

  • A microscope is an instrument used for seeing objects or living organisms that are too small to view with naked eyes or even with a magnifying glass.
  • Organisms that cannot be seen with naked eyes are called microorganisms.
  • The branch of science which deals with the study of microorganisms is called microbiology.
  • Disease causing microorganisms are known as pathogens.
  • The diseases that are caused by pathogens and transmitted through air, food, water or direct physical contact are known as communicable or infectious diseases.
  • A biological compound which is injected or introduced orally into the body of human beings to develop immunity against pathogens is called a vaccine.
  • Antibiotics are compounds which destroy or arrest the gro wth of pathogers.
  • There are four major groups of microorganisms: bacteria, fungi, algae and protozoa.
  • Viruses are borderline organisms, which are living while inside the body of their host but are non¬living when outside.
  • Protozoa are unicellular microorganisms that are found in freshwater sources. They have saprophytic mode of nutrition.
  • Bacteria are unicellular organisms.
  • In favourable conditions, bacteria reproduce by binary fission.
  • Bacteria are used in the preparation of semm and vaccines.
  • Bacteria spoil food by producing toxins.
  • Methods like dehydration, salting, deep freezing, irradiation, canning, vacuum drying, etc., are used for preserving food.
  • Food preserv ation increases the storage period of food: makes its transportation easy and helps in obtaining off-season food materials.
  • Bacteria can cause diseases like tetanus, cholera, pneumonia, typhoid and tuberculosis in human beings: black rot in cabbage; fire blight in pears and anthrax in animals.
  • Agae are autotrophic microorganisms that contain chlorophyll. They may be unicellular, multicellular or colonial.
  • Fungi are saprophytes that grow vigorously in damp, warm, dark places.
  • The process of conversion of sugar into acids, alcohol or gas by the action of yeast is known as fermentation.
  • Fermentation is usea in breweries to produce alcoholic beverages on a commercial scale.
  • Nitrogen fixation is the process by which atmospheric nitrogen is fixed for the use of plants.
  • The continuous circulation of nitrogen througi the living and non-living components of biosphere is known as the nitrogen cycle. Through this process, nitrogen is converted into its various forms.
  • Nitrogen cycle includes nitrogen fixation, ammonification, nitrification and denitrification. It maintains the percentage of nitrogen in the atmosphere.

Read and Learn More UP Board Notes for Class 8 Science

Microorganisms  Important Terms and Definitions

  • Food preservation: The process of treating food to retain its nutritive value and prevent spoilage is called food preservation.
  • Dehydration: Dehydration is the process of removing water. Canning: Canning is the process of preserving food in sterilised, air-tight cans.
  • Ammonification: The process of conversion of proteins into ammonia by the action of bacteria is called ammonification.
  • Pasteurisation: Pasteurisation is the process in which milk is heated to a high temperature and then cooled quickly to destroy almost 99% of bacteria.
  • Nitrification: Conversion of ammonia into nitrates by the action of bacteria is called nitrification.

Types of Microorganisms

  • Microorganisms cannot be seen with naked eyes and are present in almost everywhere. Microorganisms are useful as wells harmful to human beings.
  • There are four major groups of microorganisms: bacteria, fungi, algae and protozoa. Bacteria are unicellular organisms. They may be autotrophic, saprophytic or parasitic.
    Viruses are borderline organisms. They grow and multiply only inside their host When outside the body of a host, they are non-living and can be crystallised. The viruses which infects bacteria are called bacteriophage virus. Diseases like common cold, influenza, etc. are caused by viruses. Acquired Immunodeficiency Syndrome (AIDS) is a disease caused by a virus known as HIV.
  • Protozoa are unicellular microorganisms. They are found in freshwater sources like lakes, pools, etc., and have saprophytic mode of nutrition, i.e., they feed upon dead or decaying organic matter. They cause diseases like dysentery and malaria.

UP Board Notes For CLass 8 Science Chapter 2 Microorganisms Friend And Foe Types Of Microorganisms

  • Road shaped bacteria
  • Bread Mould
  • Spirogyra
  • Amoeba
  • Viruses

Microorganisms: Friend and Foe Activity 1

Aim: To observe microorganisms found in the soil
Procedure:

  1. Put some moist soil in a beaker.
  2. Add a bit of water to the beaker and stir gently.
  3. After the soil particles have settled down at the bottom, take a drop of water from this beaker and observe it under the microscope.

Observation: Tiny organisms are seen in the drop of water.
Conclusion: Microorganisms are found in soil.

Microorganisms: Friend and Foe Activity 2

Aim: To observe microorganisms found in pond water
Procedure:

  1. Collect water from a pond.
  2. Observe a drop of pond water under the microscope.

Observation: Tiny organisms are seen in the dome of water.
Conclusion: Microorganisms are found in the pond water.

Microorganisms: Friend and Foe Objective Type Questions

A. State whether the following statements are true or false.

  1. Microorganisms are found only in aquatic habitats.
  2. Microorganisms are tiny organisms which cannot be seen without a microscope.
  3. A bacterium is a microorganism.
  4. Microorganisms are not found in soil.
  5. Pond water may contain many different types of microorganisms.
  6. Protozoa are unicellular organisms.

Answers:

  1. False
  2. True
  3. True
  4. False
  5. True
  6. True

Fill in the blanks.

  1. Bacteria are useful as well as_______ to human beings.
  2. Microorganisms are found in almost all types of__________ .
  3. Viruses are___________ outside the body of a host.
  4. Most fungi are__________ .

Answers:

  1. Harmful
  2. Habitats
  3. Non-living
  4. Saprophytes

Microorganisms: Friend and Foe Short Answer Type Questions

Question 1. Why are viruses placed on the borderline between living and non-living things?
Answer
Viruses do not have cytoplasm or definite nudes. They are living only inside the body of their host Outside the host body, they can be crystallised like salt or sugar. Hence, viruses are placed on the borderline between living and non-living things.

Question 2. What is a bacteriophage?

Answer
A bacteriophage is a virus, which infects and replicates within a bacteria. Scientists are trying to use them as therapy against multi-antibiotic-resistant bacteria.

Microorganisms: Friend and Foe Long Answer Type Questions

Question 1. Describe the differences in Amoeba and Paramecium in detail.
Answer:

UP Board Notes For CLass 8 Science Chapter 2 Microorganisms Friend And Foe Difference Between Amoeba And Paramecium

Useful Microorganisms

  • Microorganisms are useful to human beings in many different ways. Bacteria and fungi are the main decomposers and help in the recycling of substances in nature. Commercially, bacteria are used for producing vinegar, rotting of flax and jute fibres, curing and ripening of tea leaves, tanning of leather, etc. The action of Lactobacillus bacteria changes milk into curd. In agriculture, bacteria help in the recycling of matter nitrogen cycle, etc. Rhizobium bacteria live in the root nodules of leguminous plants and help in fixing atmospheric nitrogen. Antibiotics such as streptomycin, Chloromycetin, etc. are obtained from bacteria. Many well-known antibiotics like penicillin are obtained from fungi. Fungi decompose dead and decaying parts of plants, animals and their waste products and make the soil fertile. Yeast is used on a large scale in bakeries, the cheese industry’ and for the production of organic acids and alcohol. At home, yeast is used for making food items such as I and dosa. etc. Mushrooms are edible fungi. Algae are used for preparing medicines, food, cosmetics and nitrogen or potassium-rich manure. Protozoa are used for the degradation of waste and sewage and as research materials.

Microorganisms: Friend and Foe Activity 3

Aim: To observe the growth of yeast in the dough
Procedure:

  1. Add some sugar and yeast power to Zi kg four (atta or maida).
  2. Add warm water and knead to make soft dough.
  3. Leave the dough for two hours and then observe it.

Observation: The dough has risen.
Conclusion: Yeast grows or reproduces rapidly in warm and wet dough releasing carbon dioxide gas. The bubbles of carbon dioxide get trapped inside the dough and hence, it rises. Therefore, the bread made with such dough is very light and spongy.

Microorganisms: Friend and Foe Activity 4

Aim: To observe the fermentation of sugar
Procedure:

  1. Fill a 500 mL beaker about 3/4th with lukewarm water.
  2. Dissolve 2-3 teaspoons of sugar into it
  3. Add half a spoon of yeast powder to this water.
  4. Leave the beaker covered for 4 – 5 hours.
  5. Smell this water after 4-5 hours.

Observation: The sugar, yeast and water mixture smells like alcohol.
Conclusion: The sugar’ has been converted into alcohol by the action of yeast This process is known as fermentation.

Microorganisms: Friend and Foe Activity 5

Aim: To observe conversion of biodegradable waste to manure
Procedure:

  1. Fill two pots halfway through with soil and able them as A and B.
  2. Fill the remainder of pot A with plant waste and the remainder of pot B with polythene bags, empty glass bottles and broken plastic toys.
  3. Cover both the pots with a cloth and leave them undisturbed for 3 – 4 weeks.
  4. Observe the pots after 3 4 weeks.

Observation: Plant waste in pot A has decomposed and changed into manure. However, polythene bags, glass bottles and plastic toys are unchanged.
Conclusion: Microbes present in the soil decompose plant waste as it is biodegradable but waste like polythene bags cannot be decomposed by microbes.

Microorganisms: Friend and Foe Objective Type Questions

A. State whether the following statements are true or false.

  1. Decomposers help in recycling of materials n nature.
  2. Milk is converted into curd by the action of algae.
  3. The process of conversion of sugar into acids, alcohol or gas by the action of yeast is known as fermentation.
  4. Penicillin is obtained from a virus.
  5. Rhizobium bacteria fix atmospheric nitrogen.

Answers:

  1. True
  2. False
  3. True
  4. False
  5. True

Microorganisms: Friend and Foe Multiple Choice Questions

1. Which of the following is an antibiotic?

  1. Lactobacillus
  2. Yeast
  3. Renin
  4. Tetracycline

2. ‘Which of the following is a microorganism?

  1. Insects
  2. Bees
  3. Yeast
  4. Frog

3. Which of the following is used for obtaining the antibiotic streptomycin?

  1. Bacteria
  2. Protozoa
  3. Yeast
  4. Algae

4. Which of the following types of fibres are obtained by the action of microorganisms on the stem of plants?

  1. Jute
  2. Cotton
  3. Wool
  4. Silk

Answers:

  1. (4) Tetracycline
  2. (3) Yeast
  3. (1) Bacteria
  4. (1) Jute

Microorganisms: Friend and Foe Short Answer Type Questions

Question 1. What are vaccines?
Answer
Vaccines are antigens of mild strains of pathogens of a specific disease. When injected into the bloodstream, they stimulate white blood cells to produce antibodies against the pathogen.

Question 2. How is bread formed?
Answer
For making bread, a bit of yeast powder and sugar are mixed with wheat flour and the flour is made into dough using warm water. Presence of warmth and sugar stimulates the growth of yeast and as a result, it multiplies rapidly releasing carbon dioxide. Bubbles of carbon dioxide make the dough to rise and hence, the bread baked with this dough is light and spongy.

Harmful Microorganisms

  • Besides being useful, microorganisms can cause a lot of harm too. The diseases which are caused by microorganisms and transmitted by air, food, water and d red physical contact are known as communicable or infectious diseases.
  • Certain human diseases caused by bacteria are tuberculosis, typhoid, cholera, leprosy, tetanus, and pneumonia.
  • Certain human diseases caused by viruses are common cold, influenza, chickenpox, smallpox, poliomyelitis, rabies, measles, AIDS and hepatitis.
  • Certain human diseases caused by fungi are, athlete’s foot, ringworm and eczema
  • Certain human diseases caused by protozoans a^, malaria and amoebic dysentery
  • Certain plant diseases caused by bacteria are, citrus canker and black rot n cabbage and animal diseases
  • Bacteria can spoil food by producing toxins in it…Algal bloom, which is the result of eutrophication, eventually leads to depletion of oxygen in water leading to loss of aquatic life forms.

Microorganisms: Friend and Foe Objective Type Questions

A. State whether the following statements are true or false.

  1. Hepatitis is caused by a virus.
  2. Pulses should be stored in wet containers.
  3. Bacteria spoil food by producing toxins in it.
  4. Malaria is caused by protozoa.
  5. Rust and smuts in plants are caused by fungi.
  6. Dehydration helps in preserving food.
  7. The bacteria which do not require oxygen for their growth are called anaerobic bacteria.
  8. Sodium benzoate is a chemical preservative.
  9. Refrigeration is storing at a high temperature.
  10. Salt is used as a preservative in jams.
  11. The foot and mouth disease is a human disease.
  12. Lactobacillus is a harmful bacterium.
  13. Tuberculosis is caused by bacteria
  14. Chickenpox and smallpox are caused by fungi.
  15. Typhoid is a communicable disease.

Answers:

  1. True
  2. False
  3. True
  4. True
  5. True
  6. True
  7. True
  8. True
  9. False
  10. False
  11. False
  12. False
  13. True
  14. False
  15. True

Microorganisms: Friend and Foe Fill in the blanks.

  1. Pathogens are the m microorganisms that cause__________
  2. Pasteurisation means heating milk to a high ‘.emperature and then immediately_______it.
  3. The most commonly used chemical food preservative is__________.
  4. Diphtheria is caused by_________.
  5. Polio, AIDS and measles are caused by_______________.
  6. Large algae that grow in oceans are called___________.

Answers

  1. Diseases
  2. Cooling
  3. Sodium benzoate
  4. Bacteria
  5. Viruses
  6. Seaweeds

Microorganisms: Friend and Foe Multiple Choice Questions.

1. ‘Which of the following microorganisms causes malaria?

  1. Virus
  2. Protozoa
  3. Bacteria
  4. Fungi

2. Which of the following microbes causes leprosy?

  1. Virus
  2. Protozoa
  3. Bacteria
  4. Fungi

3. ‘Which of the following methods is used for preserving pickles?

  1. Pasteurisation
  2. Sterilisation
  3. Salting
  4. None of these

4. Which of the following is not used as a chemical preservative for food?

  1. Vinegar
  2. Ammonia
  3. Sodium benzoate
  4. Sodium bisulphate

5. Which of the following is the best method for preserving milk?

  1. Pasteurisation
  2. Sterilisation
  3. Refrigeration
  4. Salting

6. Papad is preserved by which of the follow ng methods?

  1. Chemical preservation
  2. Salting
  3. Refrigeration
  4. Dehydration

7. Which of the following microorganisms causes food poisoning?

  1. Staphylococcus
  2. Penicillium
  3. Lactobacillus
  4. None of these

8. Which of the following microorganisms causes citrus canker in plants?

  1. Algae
  2. Fungi
  3. Bacteria
  4. None of these

Answers

  1. (b) Protozoa
  2. (c) Bacteria
  3. (c) Salting
  4. (b) Ammonia
  5. (a) Pasteurisation
  6. (d) Dehydration
  7. (a) Staphylococcus
  8. (c) Bacteria

Microorganisms: Friend and Foe Short Answer Type Questions

A. What are some of the methods that can help in preserving food?
Action of bacteria spoils food. Heating food at a very high temperature kills bacteria or storing food at a very-’ low temperature such as in a refrigerator prevents spoilage of food. Chemical preservatives such as sodium benzoate, excess of salt or sugar as in pickles and jams respectively, dehydration as in papad and canning food items are other ways that can prevent spoiling of food.

B. Name a few chemical preservatives.
Few chemical preservatives are vinegar, sodium benzoate and sodium metabisulphite.

C. Suggest some methods to prevent the growth of moulds.
Mould or fungi grow in warm and wet conditions. Hence, their growth can be prevented by:

  • Keeping the temperature low
  • Making use of clean and closed containers for storing food items
  • Keeping 0 lings dry

D. How can we stop the spread of communicable diseases?
Communicable diseases are transmitted by air, food, water and direct physical contact Spread of communicable diseases can be stopped by putting the infected person in quarantine, vaccinating against disease-causing microbes, taking full course of antibiotics prescribed by the physician, keeping our body and surroundings clean and always eating and drinking clean food and drinks.

Nitrogen Fixation

  • The continuous circulation of nitrogen through the living and non-living components of biosphere is; known as nitrogen cycle. Through this process, nitrogen is converted into its various forms. The nitrogen cycle; includes nitrogen fixation, ammonification. nitrification and denitrification. It maintains the percentage of nitrogen in the atmosphere. Rhizobium bacteria live in the root nodules of leguminous plants and blue-green algae fix atmospheric nitrogen and convert it into nitrogenous compounds.
  • Lightening too converts! atmospheric nitrogen into nitrogenous compounds. Parts of nitrogenous compounds in the soil are; converted directly into atmospheric nitrogen and the remaining is taken up by the plants. Plants convert; nitrogenous compounds to proteins. These proteins are eaten by animals and returned to soil either as I waste product of excretion or after death through decomposition by microbes.

Microorganisms: Friend and Foe Objective Type Questions

A. State whether the following statements are true or false.

  1.  Blue-green algae and Rhizobium bacteria fix atmospheric nitrogen.
  2.  Ammonification is the process of conversion of ammonia into proteins.

Answers:

  1. True
  2. False

Microorganisms: Friend and Foe Long Answer Type Questions

A. Make a flowchart to show the nitrogen cycle.

UP Board Notes For CLass 8 Science Chapter 2 Microorganisms Friend And Foe Atmospheric Nitrogen

Exercise

1. Fill in the blanks:

  1. Microorganisms can be seen with the help of a__________.
  2. Blue-green algae fix __________directly from the air to enhance the fertility of the soil.
  3. Alcohol is produced with the help of____________.
  4. Cholera is caused by_____________.

Answers:

  1. Microscope
  2. Nitrogen
  3. Yeast
  4. Bacteria

2. Tick the correct answer

1. Yeast is used in the production of

  1. Sugar
  2. Alcohol
  3. Hydrochloric Acid
  4. Oxygen

2. The following is an antibiotic:

  1. Sodium bicarbonate
  2. Streptomycin
  3. Alcohol
  4. Yeast

3.  Carrier of malaria-causing protozoan is:

  1. Female Anopheles mosquito
  2. Cockroach
  3. Housefly
  4. Butterfly

4. The most common carrier of communicable diseases is:

  1. Ant
  2. Housefly
  3. Dragonfly
  4. Spider

5. The break or idli dough rises because of:

  1. Heat
  2. Grinding
  3. Growth of yeast cells
  4. Kneading

6. The process of conversion of sugar into alcohol is called:

  1. Nitrogen fixation
  2. Moulding
  3. Fermentation
  4. Infection

Answers.

  1. (2) Alcohol
  2. (2) Streptomycin
  3. (1) Female anopheles mosquito
  4. (2) Housefly
  5. (3) Growth cf yeast cells
  6. (3) Fermentation

3. Match the Organisms in column A with their action in column B

science class 8 chapter 2 Match the Organisms in column4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
No, microorganisms cannot be seen with the naked eye because they are too small. We can see them under a microscope.

5. What are the major groups of microorganisms?
The major groups of micro-organisms are bacteria, fungi, protozoa, algae and viruses.

6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Rhizobium bacteria and blue-green alga can fix atmospheric nitrogen in the soil.

7. Write 10 lines on the usefulness of microorganisms in our lives.

The beneficial aspects of microorganisms are as follows:

  • Microorganisms are decomposers and they help in the recycling of substances.
  • Blue-green algae and Rhizobium bacteria convert atmospheric nitrogen into nitrogenous compounds and increase the fertility of the soil.
  • Lactobacillus helps in the formation of milk products like curd and cheese.
  • Yeast helps in the formation of alcohol and bakery products like bread and cakes.
  • Products like idli and dosa are prepared by the action of fungi.
  • Medicines such as penicillin are made from fungi.
  • Mushrooms are edible fungi.
  • Algal cell extract such as agar is used for preparing medicines, food and cosmetics.
  • Kelp, a brown alga, is a rich source of iodine and potassium.
  • Many types of seaweed are used as food in China and Japan.

8. Write a short paragraph on the harms caused by microorganisms.
Besides being useful, microorganisms are responsible for causing a large variety of diseases in plants, animals and human beings. They spoil food by breaking down food molecules and making new products called amines, which are generally smelly. This changes the chemical composition, texture and physical appearance of the food. Such food, if consumed, leads to many diseases including food poisoning. In plants, they cause diseases like wheat rust and citrus canker. In animals, they cause diseases like foot and mouth disease and anthrax. They spoil articles like clothes, leather, etc.

9. What are antibiotics? What precautions must be taken while taking antibiotics?

Antibiotics as chemicals that inhibit the growth of microorganisms without harming the host Precautions to be taken while taking antibiotics are:

  • Antibiotics should be taken only on the advice of a qualified doctor.
  • One must finish the entire course prescribed by the doctor.
  • Antibiotics, however, are not effective against colds and flu as these diseases are caused by viruses.

Microorganisms: Friend and Foe Hots Corner

A. Your mother makes curd at home. The curd sets faster in summers than in winters. Why?
Curd, as we know, is formed by the action of Lactobacillus bacteria on milk. Bacteria, including Lactobacillus, can grow and multiply faster during summer as the temperature in summer is appropriate for their growth. Hence, curd sets faster in summers than in winters.

B. Why packets of chips are filled with nitrogen gas rather than with oxygen?
Nitrogen inhibits the growth of aerobic bacteria and the chips stay fresh and are not spoilt by the action of bacteria. Thus, packets of chips are filled with nitrogen gas rather than oxygen.

C. Sameer bought fruit chat from a vendor. Next day he fell ill. What do you think is the reason for his illness?
Fruit chat vendors keep cut fruits in the open for long hours. This invites action of bacteria and they grow and multiply on these fruits. Hence, the toxins produced in the fruits are consumed along with fruit chat and they might be responsible for causing the illness.

D. Dough gets spoilt faster than dry flour. What is the reason behind it?
The dough contains moisture, which is essential for the growth of microorganisms. Dry flour does not have any moisture. Hence, dough gets spoilt faster than dry flour.

Practice Exercise

Objective Type Questions

A. Fill in the blanks.

  1. A bacterium which infects a virus is known as a.
  2. Disease-causing microorganisms are called.
  3.  Milk is preserved by the process of.

Answers:

  1. Bacteriophage
  2. Pathogens
  3. Pasteurisation

B. Circle the odd one out.

  1.  Bacteria, fungi, houseflies, algae, protozoa
  2. Chickenpox, pneumonia, smallpox, polio, rabies
  3. Nitrogen fixation, ammonification, nitrification, fermentation, denitrification

Answers:

  1. Housefly
  2. Pneumonia
  3. Fermentation

C. State whether the following statements are true or false.

  1. Spoilage of food by bacterial action can be prevented by dehydration, salting or adding preservatives.
  2. No other organisms besides bacteria are able to fix atmospheric nitrogen.

Answers:

  1. True
  2. False

D. Multiple-Choice Questions

1. Which of the following are used in making body items?

  1. Mushroom
  2. Seaweed
  3. Yeast powder
  4. All of these

2 Which of the following are autotrophic?

  1. Protozoa
  2. Algae
  3. Fungi
  4. Virus

3. Which of the following helps in the nitrogen cycle?

  1. Rhizobium bacteria
  2. Blue-green algae
  3. Lightening
  4. All of these

4. Which of the following is a disease caused in plants by pathogens?

  1. Foot and mouth disease
  2. Rabies
  3. Citrus canker
  4. Tuberculosis

5. Which of the following is a communicable disease?

  1. Typhoid
  2. Cancer
  3. Diabetes
  4. Asthma

Answers:

  1. (d) All of these
  2. (b) Algae
  3. (d) All of these
  4. (c) Citrus canker
  5. (a) Typhoid

Microorganisms: Friend and Foe Short Answer Type Questions

A. What is ALDS? 
AIDS stands for Acquired Immuno Deficiency Syndrome and is caused by the HIV (Human Immunodeficiency Virus) virus. In this disease, there is severe loss of the body’s immunity and the body j becomes highly susceptible to diseases.

B. What is food preservation?
The process of treating food to retain its nutritive value and prevent its spoilage is called food preservation. Dehydration, salting, deep freezing, irradiation, canning, vacuum drying, etc., are some of the methods used for preserving food. Food preservation increases the storage period of food; makes its transportation easy and helps in obtaining off-sensor food materials.

 

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions

by

Cell Structure And Functions Chapter Objectives

  • Cells are the building blocks of all living organisms. Therefore, a cell is the smallest basic structural unit of life.
  • The shape and size of a cell depend on its functions.
  • The size of a cell is measured in micrometers (um) or microns.
  • Most cells are microscopic and can only be seen when enlarged or magnified under a microscope.
  • The size of the cell is not related to the size of the organism. An organism with billions of cells begins life as a single cell.
  • Organisms made up of only one cell are called unicellular organisms such as Amoeba, Paramecium, Euglena, bacteria, etc.
  • Organisms made up of more than one cell are called multicellular organisms.
  • A typical cell consists of three parts namely- cell membrane, cytoplasm, and nucleus. The cell membrane of plant cells is surrounded by an additional outer thick layer known as their cell wall.
  • Cell wall supports and safeguards the plants’ cells against temperature changes, high wind speed, moisture, etc.
  • Cytoplasm is a thick, jelly-like substance present inside the cell.
  • Different cell organelles present in the cytoplasm are mitochondria, plastids, Golgi bodies, endoplasmic reticulum, vacuoles, lysosomes, ribosomes, and centrosomes.
  • Plastids and vacuoles are present only in plant cells.
  • The centrosome is present only in animal cells.
  • Non-living substances such as water, sugar, minerals, proteins, lipids, etc. are also present in the cytoplasm.
  • The nucleus is the most important part of a cell. It is located within the cytoplasm at the center of the cell.
  • The nucleus consists of the nuclear membrane, nucleoplasm, nucleolus, and chromosomes.
  • The nuclear membrane is the thin semi-permeable membrane that separates the nucleus from the cytoplasm.
  • The nucleolus is a small spherical body present within the nucleus. The main function of nucleolus is to synthesize ribosomes.
  • Chromosomes possess genes or the units of heredity of living organisms.

Read and Learn More UP Board Notes for Class 8 Science

Cell Structure And Functions Important Terms And Definitions

Tissue: It is a group of similar cells that perform various specific functions.
Organ: It is a group of similar types of tissues to perform a particular function.
Organelles: These are the smaller components of the cell that perform various functions in the cell.
Gene: These are the carriers of hereditary characters from one generation to another.
Pseudopodia: The false foot present in the amoeba that performs locomotion and helps to trap the food particles called pseudopodia.
Cell inclusions: Non-living constituents of the cell are known as cell inclusions.
Prokaryotic cells: The cells without well-organized nuclear material are called prokaryotic cells.
Prokaryotes: The organisms having prokaryotic cells are called prokaryotes. For example, bacteria and blue-green algae.
Eukaryotic cells: The cells which have a well-organized nucleus along with the nucleus membrane are called eukaryotic cells.
Eukaryotes: The organisms having eukaryotic cells are called eukaryotes. For example, onion cells, human cheek cells, etc.

Cells: The Basic Unit of Life

  • Cells are the basic structural and functional unit of a living organism. Cells are complex living structures. Robert Hooke discovered the cell in 1665.
  • Organisms made of a single cell are known as unicellular organisms, for example, Amoeba, Paramecium, Euglena, etc. Organisms made of several cells are called multicellular organisms.
  • Cells can be spherical, spindle, or long branched like in red blood cells, muscle cells, and nerve cells respectively. Generally, cells are microscopic and are not visible to the unaided eye. By using a microscope they can be magnified or enlarged.
  • A group of specialized cells together form the tissues. Tissues are in turn grouped to form specified structures called organs.

Cell Structure And Functions Objective Type Questions

A. State whether the following statements are true or false.

  1. Organisms made of more than one cell are called multi-cellular organisms.
  2. Cells are complex non-living structures.
  3. Most cells can be seen by unaided eyes.
  4. Cells are the basic structural unit of all living organisms.
  5. Pseudopodia helps Amoeba in moving and capturing food.

Answers:

  1. True
  2. False
  3. False
  4. True
  5. True

B. Multiple Choice Questions.

1. Which one of the following is a unicellular organism?

  1. Elephant
  2. Rat
  3. Humans
  4. ParameciumAnswers. (4)Paramecium

2. In which one of the following organisms is aispseudopodia found?

  1. Paramecium
  2. Amoeba
  3. Bacteria
  4. None of these
    Answers.     (2)Amoeba

3. Who discovered cells?

  1. Theodor Schwann
  2. Albert Einstein
  3. Robert Hooke
  4. Matthis jakkob

Answers: (3)c)Robert Hooke

Parts of the Cell

The basic structure of all cells comprises three main parts: the cell membrane or plasma membrane, cytoplasm, and nucleus. The cell membrane also known as the plasma membrane is a thin, delicate layer that protects the cells, gives them a definite shape, and separates one cell from the other. It surrounds the cytoplasm and the nucleus.
Cytoplasm is a thick, jelly-like substance present between the cell membrane and the nucleus. It contains different cell organelles and other nonliving substances.
The nucleus controls all the activities of the cell and regulates its growth. A thin membrane called the nuclear membrane separates the nucleus from the cytoplasm. A small round-shaped body called na nucleolus is present within the nucleus. Thread-like structures called chromosomes are also present in the nucleolus, which carry genes.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Part Of Cells

Cell Structure and Functions Activity 3

Aim: To observe the basic components of the cells.
Procedure:

  1. Peel off the dry pink covering of the onion bulb using forceps or your hand.
  2. Separate the thin layers of onion peel from inside the onion bulb using forceps.
  3. Cut the separated onion peel into smaller pieces with the help of forceps.
  4. Put a drop of water on the glass slide and place the onion peel.
  5. Put a drop of methylene blue solution on the onion peel and cover with overslip.
  6. Place the slide under the microscope and observe it.

Observation:

Several cells can be seen lying side-by-side bound by the cell membrane and an additional layer called the cell wall. A spherical-shaped nucleus is present in the center of each cell.

Conclusion:

The basic components of all cells are the cell membrane, nucleus , and cytoplasm. The cell wall is an additional layer present in plant cells.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Part Of Cell Membrane

Cells observed in an onion peel

Cell Structure And Functions Activity 4

Aim: To study the human cheek cells
Procedure:

  1. Break the tip of a clean toothpick or matchstick and use it to scratch the inside of your cheek gently.
  2. Put a drop of water on the glass slide and place the scraping on it.
  3. Add a drop of iodine or a few drops of methylene blue solution to it.
  4. Place the slide under the microscope and observe it.

Observation:

The cells do not have any definite shape and are enclosed within a thin cell membrane. The cell wall is not seen around the cells.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Activty 4

Conclusion:
The basic components of all cells are the cell membrane, nucleus, and cytoplasm. The cell wall is not present in animal cells.

Cell Structure and Functions Objective Type Questions

A. State whether the following statements are true or false.

  1. The nucleus is located in the center of the cell.
  2. Cytoplasm separates the cells from their surroundings.
  3. Animal cells have cell walls
  4. The nuclear membrane separates the nucleus from the cytoplasm.

Answers:

  1. True
  2. False
  3. False
  4. True

B. Multiple-Choice Questions

1. Which of the following cell organelles is present within the nucleus?

  1. Lysosomes
  2. Ribosomes
  3. Chromosomes
  4. Centrosome

Answers. 3) Chromosomes

2. Which of the following cell organelle is referred to as the ‘powerhouse of the cells?

  1. Mitochondria
  2. Protoplasm
  3. Plastids
  4. Ribosomes

Answers. 1) Mitochondria

3. Where does protein synthesis take place in a cell?

  1. Golgi bodies
  2. Endoplasmic Reticulum
  3. Vacuoles
  4. Ribosomes

Answers. 2) Endoplasmic Reticulum

Cell Structure And Functions Short Answer Type Questions

A. Why is the plasma membrane also called an electively permeable membrane?

A plasma membrane allows only certain substances such as water and minerals to flow in and out of the cell hence, it is also called a selectively permeable membrane.

B. What is the function of genes?

Genes transfer hereditary features from parents to their offspring.

Comparison of Plant and Animal Cell

Cell organelles present in animal cells are the same as those in plant cells; however, some cell organelles are present only in plant cells. In plant cells, the cell membrane is surrounded by an additional outer thick layer known as the cell wall which gives rigidity and shape to these cells. Plant cells contain some colored cell organelles, these are called plastids. Plastids that contain green colored pigment chlorophyll are called chloroplasts. Cells also contain certain blank-looking structures in the cytoplasm. These structures are called vacuoles. Vacuoles are large and common in plant cells and much smaller in animal cells.

Cell Structure And Functions Objective Type Questions

A. Fill in the blanks.

  1. Chlorophyll present in leaves is essential for______
  2. Colored pigments present in the cells of the leaves are called_______

Answers: 1. Photosynthesis 2. Plastids

B. State whether the following statements are true or false.

  1. The membrane of an animal cell is surrounded by an additional layer.
  2. Vacuoles are more prominent in plant cells.

Answers: I. False 2. True

Cell Structure And Functions Short Answer Type Questions

A. What are the differences between cell walls and cell membranes

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Difference Between Cell Membrane And Cell Wall

Differences between cell wall and cell membrane are:

Cell Structure and Functions Textbook exercises

1. Indicate whether the following statements are True (T) or False (F).

  1. (Unicellular organisms have one-celled body.
  2. Muscle cells are branched.
  3. The basic living unit of an organism is an organ.
  4. Amoeba has an irregular shape.

Answer:

  1. True
  2. False
  3. False
  4. True

2. Sketch the human nerve cell. What functions do nerve cells perform?

The nerve cells receive and transfer messages as well as control and coordinate the functioning of different parts of the body.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions The human nerve cell

A human nerve cell

3. Write short notes on the following.

(a) Cytoplasm (b) Nucleus of a cell

(a) Cytoplasm is a thick, jelly-like substance present between the cell membrane and the nucleus. Various cell organelles such as mitochondria, ribosomes, plastids, etc. are present in the cytoplasm. It also contains non-living substances such as water, sugar, minerals, lipids, proteins, etc.

(b) The nucleus controls all the activities of the cell and regulates its growth. A thin membrane called the nuclear membrane separates the nucleus from the cytoplasm. A small round-shaped body called a nuclear Eolus is present within the nucleus. Thread-like structures called chromosomes are also present in the nucleolus, which carries genies or the hereditary unit of living organisms.

4. Which part of the cell contains organelles?

Cytoplasm present between the cell membrane and the nucleus contains the various cell organelles.

5. Make sketches of plant and animal cells. State three differences between them.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Plant Cells And Animal Cells

6. State the difference between eukaryotes and prokaryotes.

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Eukaryotes vs prokaryotes

7. Where are chromosomes found in a cell? State their function.

Chromosomes are found in the nucleus of a cell. Chromosomes carry genes and help in the inheritance i.e. transfer of characteristics from the parents to the offspring.

8. ‘Cells are the basic structural unit of living organisms. Explain.

As bricks are put together to construct a building, similarly, the body of a living organism is formed of cells. All the basic life functions of an organism occur in the cell. A group of cells forms a tissue that performs a specific function. Different tissues combine to form an organ and different organs together form organ systems which in turn form an organism. Hence, cells are referred to as the basic structural unit of life.

9. Explain why chloroplasts are found only in plant cells. Chloroplasts are green-colored plastids. They are green in color due to the presence of chlorophyll in them. Chlorophyll is vital for photosynthesis as it traps solar energy and uses it to produce food for the plant.

10. Complete the crossword with the help of the clues given below:

UP Board Notes for Class 8 Science Chapter 8 Cell Structure and Functions Cross And Down

Across:

  1. This is necessary for photosynthesis.
  2. Term for the component present in the cytoplasm.
  3. The living substance in the cell.
  4. units of inheritance present on the chromosomes.

Down:

  1. Green plastids.
  2. Formed by a collection of tissues.
  3. It separates the contents of the cell from the surrounding medium.
  4. Empty structure in the cytoplasm.
  5. A group of cells.

Across:

  1. Chlorophy
  2. Organelles
  3. Protoplasm
  4. Genes

Down:

  1. Chloroplasts
  2. Organ
  3. Membrane
  4. Vacuole
  5. Tissue

Cell Structure and Functions Hotscorner

A. If you are given two slides, one with an animal cell and the other with a plant cell, how will you differentiate between the animal and the plant cell?

When two slides are observed under a microscope, the cell which shows a well-defined cell wall is a plant cell and the one which does not have a defined cell wall is an animal cell.
The cells with a large number of vacuoles and chloroplasts are plant cells and the cells that lack chloroplast and have a less number of vacuoles are animal cells.

B. Do rats and elephants have nerve cells of different sizes? Give reasons for your answer.

Nerve cells in both rats and elephants are long and branched as they both perform the function of receiving and transmitting messages. This is because the size of a cell depends upon its function and not on the size of the body of the living organism.

Cell Structure and Functions Practice exercise

Objective Type Questions

A. Give one word for the following.

  1. The living part of the cytoplasm.
  2. The thread-like structures within the nucleus.
  3. The most important part of a cell.
  4. The site of protein synthesis.
  5. The measurement unit of the size of the cell.

Answers:

  1. Protoplasm
  2. Chromosomes
  3. Nucleus
  4. Ribosomes
  5. Micron

B. Fill in the blanks.

  1. The powerhouse of the cell is______
  2. ______are referred to as the suicidal bags of cells.
  3. _______synthesize, store, and secrete enzymes and proteins.
  4. Organisms made of more than one cell are called______

Answer:

  1. Mitochondria
  2. Lysosomes
  3. Golgi bodies
  4. Multicellular

C. State whether the following statements are true or false.

  1. The size of the cell is not related to the size of the organism.
  2. Amoeba do not have a definite shape as pseudopodia keep appearing and disappearing.
  3. Cells are visible to the naked human eye.
  4. Lysosomes help in protein synthesis.
  5. Plastids are present in both animal and plant cells.

Answer:

  1. True
  2. True
  3. False
  4. False
  5. False

D. Multiple Choice Questions.

1. Which of the following selectively permeable membranes is present around the cells?

  1. Nuclear membrane
  2. Cell membrane
  3. Nucleosome
  4. Cell wall

Answers. 2) Cell membrane

2. Which of the following cell organelle is also called the control center of the cell?

  1. Mitochondria
  2. Nucleus
  3. Cell membrane
  4. Cytoplasm

Answer. 2) Nucleus

3. Which of the following are referred to as the ‘kitchen of the cell’?

  1. Ribosomes
  2. Centrosome
  3. Leucoplasts
  4. chloroplasts

Answer. 4) chloroplasts

4. Which of the following are colorless plastids?

  1. Chloroplasts
  2. Leucoplasts
  3. Chloroplast
  4. None of these

Answer. 2) Leucoplasts

5. Which of the following is a multicellular organism?

  1. bacteria
  2. Amoeba
  3. Euglena
  4. Fungi

Answer. 4) Fungi

6. Which of the following organelles is not found in an animal cell?

  1. Lysosomes
  2. Ribosomes
  3. Endoplasmic Reticulum
  4. Chloroplasts

Answer: 4) Chioroplats

Also Read

UP Board Notes for Class 8 Science Chapter 3 Synthetic Fibres and Plastics

by

Synthetic Fibres and Plastics Concepts

  1. Types of Synthetic Fibres
  2. Characteristics of Synthetic Fibres
  3. Plastics
  4. Plastics and the Environment

Synthetic Fibres and Plastics Learning Objectives:

  •  Fibres made by human beings are called synthetic fibres. Rayon, nylon, polyester, acrylic, etc., are examples of synthetic fibres.
  • A synthetic fibre is a chain of small units joined together to form a large single unit called a polymer.
  • Rayon or artificial silk resembles silk in appearance, texture and shine. It is made from the chemical treatment of wood pulp.
  • Rayon can be woven like silk fibres and can be dyed in many different colours. It is used for making saris, dresses, aprons, caps, carpets, etc.
  • Nylon is made without using any animal or plant-based raw material. It is made from coal, water and air.
  • Nylon fibre is strong, elastic, wrinkle-free, light and absorbs little water. It is the first fully-synthetic fibre. It is lustrous and easy to wash.
  • Due to high tensile strength of nylon fibre, it is used for making parachute fabric, ropes for climbing mountains, etc.
  • Polyester is made up of units of a chemical called ester a compound which gives fruits their fruity smell.
  • Polyester is easy to wash, does not get wrinkled and is suitable for making shirts, dresses, etc. Terylene and PET (Polyethylene terephthalate) are examples of polyester.
  • Terylene is used for making fine fabrics and PET is used for making bottles, jars, etc.
  • Many fabrics are made by mixing two types of fibres. For example, poly cot is made by mixing polyester and cotton and poly wool is made by mixing polyester and wool.
  • Acrylic is another type of synthetic fibre, which is used for making sweaters, shawls and blankets.
  • Synthetic fibres are less expensive, available in many different colours, have high tensile strength, durable and easy to maintain.
  • On heating, synthetic fibres melt. They do not absorb moisture and can catch fire easily.
  • Plastic is also a polymer like synthetic fibres. However, the arrangement of small units is not the same in all types of plastic.
  • Plastics which can be bent easily and deforms on heating are known as thermoplastics. Polythene and PVC (polyvinyl chloride) are thermoplastics and are used for making toys, combs, containers, etc.
  • Plastics which cannot be softened by heating are called thermosetting plastics. Examples of thermosetting plastics include Bakelite and Melamine.
  • Bakelite is a poor conductor of electricity and heat and is used for making electric switches and handles of kitchen utensils.
  • Melamine resists fire and can tolerate heat better than other types of plastics, it is used for making tiles, utensils and fabrics that resist fire.
  • Plastics are poor conductors of heat and electricity and that is why electric wires and electric equipment are covered with plastic.
  • Plastics are lightweight, not very expensive, non-reactive and have good strength.
  • Plastic is used in healthcare industry for making syringes, threads that are used for stitching wounds, packaging of medicines, surgical gloves and medical instruments.
  • Special plastic cookware is used for cooking or heating food in the microwave ovens.
  • Teflon is a special plastic on which water and oil do not stick, it is used as a non-stick coating on cookware.
  • Plastic is non-biodegradable, i.e. it cannot be decomposed through natural processes. Some plastics take many years to decompose.
  • Animals eating the food wastes swallow polythene bags which choke their respiratory
  • system and lead to their death. Polythene bags clog drains too.
  • We should avoid the use of polythene bags and should use reusable cloth or jute bags.
    We should segregate waste into biodegradable and non-biodegradable ‘Waste before throwing them. We should not throw garbage or wrappers anywhere other than the garbage bins.
  • We should recycle plastic as much as possible. However, recycled plastic cannot be used for storing food.
  • To reduce plastic pollution one should avoid its use as much as possible and use biodegradable plastics.
  • We must remember the 4 R principle: Reduce, Reuse, Recycle and Recover.

Read and Learn More UP Board Notes for Class 8 Science

Types of Synthetic Fibres

  • We wear clothes that are made up of different types of fabrics. Fabrics are made of fibres. There are two types of fibres: natural and man-made. Silk, cotton, wool, etc. are natural fibres because they are obtained from natural resources. Fibres made by human beings are called synthetic fibres. Rayon, nylon, polyester, acrylic, etc., are examples of synthetic fibres.

Synthetic Fibres and Plastics Activity 1

Aim: To test, the strength of different threads or fibres
Procedure:

  1. Tie a 60 cm long cotton thread to the clamp of a stand.
  2. At the free end of the thread, tie a very small pan so that small weights or marbles can be placed on it
  3. One by one, add weights or marbles to the pan till the cotton thread breaks.
  4. Note down the total weight or the total number of marbles that broke the cotton thread.
  5. Repeat these steps with woollen, silk and nylon threads of the same thickness and length.
  6. Record your observations.

UP Board Notes For CLass 8 Science Chapter 3 Symthetic Fibers And Plastics Activity 1

An iron stand with a thread hanging from the clamp

Observation: The weight required to break the threads made out of cotton, wool, silk and nylon fibres varied with the thickness of the threads. However, for the threads having the same thickness and length, nylon required the highest weight or number of marbles to break ft.
Conclusion: Nylon thread requires the highest weight to break. Nylon fibres are stronger than woollen, silk and cotton fibres.

Objective Type Questions

A. State whether the following statements are true or false.

  1. Nylon is used for manufacturing tyres and high-strength ropes.
  2. Rayon is a natural fibre.
  3. Fibres obtained from natural resources such as plants and animals are called natural fibres.
  4. All synthetic fibres are obtained from plants or animals.

Answers.

  1. True
  2. False
  3. True
  4. False

B. Fill in the blanks.

  1. _________stands for Polyethylene terephthalate.
  2. The process in which a large number of simple molecules combine chemically to form a giant molecule is called_________.
  3. Rayon is obtained from_______.

Answers.

  1. PET
  2. Polymerisation
  3. Wood pulp

Short Answer Type Questions

Question 1. Why is nylon used for making parachute cloth and ropes for mountain climbing?

Answer
Nylon fibres are very strong and have very high tensile strength. Hence, they are used for making parachute cloth and ropes for mountain climbing.

Question 2. Some people do not consider rayon a truly synthetic fibre. Why?

Answer
All synthetic fibres are made from raw materials of petroleum origin called petrochemicals. Rayon, on; the other hand, is made from chemical treatment of wood pulp. Wood is obtained from plants and hence, rayon is not considered to be a truly synthetic fibre.

Characteristics of Synthetic Fibres

  • Synthetic fibres are strong, light and durable. Fabrics made from synthetic fibres do not absorb water, are wrinkle free and easy to maintain. Fabrics made from synthetic fibres are available in many different colours and usually less expensive. For example, rayon or artificial silk is lustrous, can be woven like silk and much less expensive than silk On heating, synthetic fibres melt and can easily catch fire.

Synthetic Fibres and Plastics Activity 2

Aim: To observe the amount of water absorbed by cloth Dieces made from natural and synthetic fibres
Procedure:

  1. Take two cloth pieces of same size, one cotton and the other polyester.
  2. Put equal amount of water in two mugs of the same size.
  3. Soak the two cloth pieces into the two mugs.
  4. Take the cloth pieces out of the mugs after five minutes and spread them in the Sun to dry.
  5. Compare the amount of water left in the two mugs.

Observation: The mug that had the cotton cloth soaked in it has a lesser amount of water left than the one in which the polyester cloth was soaked.
Conclusion: Synthetic fibres absorb very little water as compared to natural fibres.

Objective Type Questions

A. State whether the following statements are true or false.

  1. Fabrics made from synthetic fibres are usual y wrinkle-resistant.
  2. Synthetic fibres melt on heating.
  3. Fabrics made from natural fibres are less expensive as compared to the ones made from synthetic fibres.
  4. Synthetic fabrics are not durable.

Answers

  1. True
  2. True
  3. False
  4. False

B. Fill in the blanks.

  1. fibres can be dyed into many different colours.
  2. Clothes made from synthetic fabrics are durable and easy to.
  3. Synthetic fibres do not absorb
  4. We should not wear clothes made Tom synthetic fibres while working near.
  5. Wool is but its synthetic counterpart, acrylic, is cheap.

Answers.

  1. Synthetic
  2. Maintain
  3. Water
  4. Fire
  5. Expensive

Plastics

  • Like synthetic fibres, plastic is also a polymer However, the arrangement of other small units is not same in all types of plastic. In some plastics, the arrangement is linear and in others it is cross-linked. Plastics can be melted and moulded into desired shapes. They can be recycled, coloured into different colours, rolled; into sheets and drawn into wires. Polythene is an example of plastic.

Objective Type Questions

A. State whether the following statements are true or false.

  1. Thermoplastics become hard on heating.
  2. Plastics are lightweight and durable.
  3. Teflon does not let oil and water stick to it.
  4. Plastics have no use in the medical industry.
  5. The arrangement of small units in some plastics is linear, while in others it is cross-linked.

Answers.

  1.  False
  2. True
  3. True
  4. False
  5. True

B. Fill in the blanks.

  1. The clothes of firefighters are made fire resistant by using____________.
  2. Polythene bags are made out of____________.
  3. Bakelite and melamine are examples of_____________ plastics.
  4. _______________coating is used in non-stick cookware.

Answers.

  1. Melamine
  2. Plastic
  3. Thermosetting
  4. Teflon

C. Multiple Choice Questions.

1. Which of the following describes plastics?

  1. Strong and corrosion resistant
  2. Weak and prone to corrosion
  3. None of these
  4. Good conductor of heat and electricity

2. Which of the following is true about PVC?

  1. Polyvinyl chloride
  2. Thermoplastic
  3. Bends easily
  4. All of these

3. Which of the following are the characteristics of plastics?

  1. Can be moulded easily into various shapes
  2. Are good conductors of heat
  3. None of these
  4. Are Delicate

4. Which of the following applies to melamine?

  1. Thermoplastic
  2. Fire resistant
  3. Bends easily
  4. Weak

5. Which of the following is the most commonly used form of plastic?

  1. PVC
  2. Bakelite
  3. Melamine
  4. Polythene

Answers.

  1. (1) Strong and corrosion resistant
  2. (4) All of these
  3. (1) Can be moulded easily into various shapes
  4. (2) Fire resistant
  5. (4) Polythene

Synthetic Fibres and Plastics Short Answer Type Questions

Question 1. List a few uses of polythene.

Answer
Polythene sheets are used as packaging material. Polythene containers and pipes are used for storing and transporting water, oil and other materials. Polythene is also used as a water-proofing material.

Question 2. What is bakelite? Why is it used to make handles of utensils and most electrical fittings such as electrical switches, sockets, etc.?

Answer
Bakelite is a thermosetting plastic. It is a poor conductor of heat and electricity. Therefore, it is used for making handles of utensils and most electrical fittings.

Plastics and the Environment

  • Disposal of plastic is a major problem. Plastic is non-biodegradable, i.e., it cannot be decomposed through; natural processes. Some plastics take many years to decompose. Plastics are not environmentally friendly. It  does not get completely burnt and releases poisonous gases on burning, which pollutes the environment ;

Objective Type Questions

A. State whether the following statements are true or false.

  1. Plastic is non-biodegradable.
  2. To dispose of plastic, we should bum it
  3. Polythene bags choke animals when they accidentally ingest them.
  4. To reduce pollution, we must remember the principle to reduce, reuse, recycle and recover.
  5. Candy wrappers can be thrown on the side of the roads.
  6. It is best to use recycled Plastic containers for storing food.
  7. To reduce plastic pollution, we should avoid the use of non-biodegradable plastic.

Answers.

  1. True
  2. False
  3. True
  4. True
  5. False
  6. False
  7. True

B. Match the items in column A with those in column B.

Match the items in column A with those in column B.

Synthetic Fibres and plastics Textbook Exercises

Question 1. Explain why some fibres are called synthetic.

Answer
Some fibres are called synthetic because they are made by human beings. The raw materials used for preparing synthetic fibres are petrochemicals.

Question 2. Mark the correct answer.
Rayon is different from synthetic fibres because:

  1. It has a silk-like appearance.
  2. It is obtained from wood pulp.
  3. Its fibres can also be woven like those of natural fibres.

Answer.

2.  It is obtained from wood pulp.

Question 3. Fill in the blanks with appropriate words.

  1. Synthetic fibres are also called ________or___________fibres.
  2. Synthetic fibres are synthesised from a raw material called____________.
  3. Like synthetic fibres, plastic is also a____________.

Answers.

  1. Man-made, artificial
  2. Petrochemicals
  3. Polymer

Question 4. Give examples which indicate that nylon fibres are very strong.

Answer
Parachutes, ropes used for mountain climbing and tents are made of nylon and this indicates that nylon fibres are very strong.

Question 5. Explain why plastic containers are favoured for storing food.


Answer
Plastic containers are favoured for storing food because:

  • Plastic does not react with food, air or water.
  • Plastic is strong and lightweight.
  • Plastic containers come in many different sizes, shapes and colours.

Question 6. Explain the difference between thermoplastic and thermosetting plastics.
Answer:

UP Board Notes For CLass 8 Science Chapter 3 Symthetic Fibers And Plastics Thermoplastic And Thermosetting

Question 7. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles (b) Electric plugs/switches/plug boards

Answer.
(a) Saucepan handles are made of thermosetting plastics because thermosetting plastic is a bad conductor of heat and does not deform on heating.
(b) Electric plugs/switches/plug boards are made of thermosetting plastic because thermosetting plastic is a bad conductor of electricity and hence, reduces the risk of an electric shock

Question 8. Categorise the materials of the following products into ‘can be recycled and ‘cannot be recycled. Telephone instruments, plastic toys, cooker handles, carry bags, ballpoint pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches?

Answer
Can be recycled: Plastic toys, carry bags, ballpoint pens, plastic bowls, plastic chairs
Cannot be recycled: Telephone instruments, cooker handles, plastic coverings on electric wires, electrical switches

Question 9. Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Answer
Rana should buy cotton shirts because cotton has pores that let the air in and out. On the other hand, synthetic fabrics are very tightly woven and hence, they do not allow air to pass in and out. Cotton clothes soak sweat and give a dr/ feeling, while synthetic clothes have little water-absorbing properties.

Question 10. Give examples to show that plastics are non-corrosive in nature.

Answer
Plastics do not react with air and water and hence, they do not corrode. Plastics do not decompose when left in the open for a long. For example, water is kept in plastic bottles, and pickles and food items are stored in plastic containers because the bottles or the containers do not corrode.

Question 11. Should the handle and bristles of a toothbrush be made of the same material? Explain your answer.

Answer
No. different mater also should be used for making handles and bristles of a toothbrush because bristles help in cleaning the teeth and the handle is just to support them. Bristles must be soft, and delicate and should be designed to clean teeth well, while the handle should be hard and rigid.

Question 12. ‘Avoid plastics as far as possible. Comment on this advice.


Answer:
Plastics are not environmentally friendly. They release poisonous gases on bum ng. They are non-biodegradable and hence, pollute soil, water and air. Animals choke on swallowing polythene bags and die. Polythene bags also clog the drains. Therefore, the use of plastic should be avoided as far as possible.

Question 13. Match the materials in column A with their characteristics given in column B.
Answer:

Match the materials in column

Question 14. ‘Manufacturing synthetic fibres is actually helping in the conservation of forests. Comment.


Answer
Natural fibres are obtained from natural resources, i.e., plants and animals. On the other hand, synthetic fibres are made from petrochemicals and not from forests or plants. Thus, for manufacturing synthetic fibres we do not need to cut trees or use products obtained from animals.

Question 15. Describe an activity to show that thermoplastics are poor conductors of electricity.

Answer:
Take a few items made of thermoplastics such as a piece of PVC pipe and a toy. Now set up the circuit as shown in the given illustration and one by one insert the thermoplastic item between terminals A and B. If the bulb starts glowing, then the item is a good conductor of electricity. Otherwise, it is a bad conductor of electricity. You would find that the bulb would not glow with any of the items made of thermoplastics. This indicates that thermoplastics are bad conductors of electricity.

UP Board Notes For CLass 8 Science Chapter 3 Symthetic Fibers And Plastics thermoplastics are poor conductors of electricity

Synthetic Fibres and Plastics Hots Corner

Question 1. On Diwali, we are told not to burst crackers while wearing synthetic clothes. Why?

Answer
Synthetic clothes melt on heating and stick to the skin of the person wearing them. This can result in really bad bums and hence, it is advised not to wear synthetic clothes while working near the fire.

Question 2. Plastics are very useful as well as less expensive than other materials. Which characteristics of plastics make them harmful to the environment?

Answer
Plastics are non-reactive. They do not get corroded by air or water. Hence, they do not biodegrade; and this is the property which makes them harmful to the environment.

Practice Exercise Objective Type Questions

A. Fill in the blanks.

  1. ____________is used for making sweaters, shawls and blankets.
  2. Synthetic fibres are strong but light in______________.
  3. Thermoplastics become ______________on heating.

Answers

  1. Acrylic
  2. Weight
  3. Deformed

B. Circle the odd one out.

  1. Nylon, rayon, polyester, silk, acrylic
  2. Terrycot, poly cot, nylon, poly-wool, terry wool
  3. Handles of cookware, firefighter clothes, car paint, melamine tray, water bottle

Answers

  1. Silk
  2. Nylon
  3. Water bottle

C. State whether the following statements are true or false.

  1. Polycot is made by mixing polyester and wool.
  2. Bakelite is a bad conductor of heat and electricity.
  3. Plastics are weak and non-resistant to corrosion.

Answers

  1. False
  2. True
  3. False

D. Multiple Choice Questions.

1. Which of the following is used for making electrical switches?

  1. Teflon
  2. Polythene
  3. Bakelite
  4. PVC

2. ‘Which of the following types of plastic would you use to ma<e baby toys?

  1. Bakelite
  2. Melamine
  3. Teflon
  4. Thermoplastic

3. ‘What do you call a large unit which is made up of many smaller units of the same type?

  1. Polymer
  2. Compound
  3. Element
  4. None of these

4. ‘Which of the following can be made with thermosetting plastics?

  1. Combs
  2. Bottles
  3. Buckets
  4. All of these

5. Why are electrical wires covered with a plastic covering?

  1. Plastic is durable
  2. Plastic is a bad conductor of electricity
  3. Plastic is light-weight
  4. Plastic is not very expensive

Answers

  1. (3) Bakelite
  2. (4) Thermoplastic
  3. (1) Polymer
  4. (4) All of these
  5. (2) Plastic is a bad conductor of electricity

Synthetic Fibres and Plastics Short Answer Type Questions

Question 1. What is polyester?

Answer
Polyester is made up of units of a chemical called ester-a compound which gives fruits their fruity smell Polyester is easy to wash and does not get wrinkled. Terylene and PET (Polyethylene terephthalate) are examples of polyesters.

Question 2. Why does hot water deform water bottles?

Answer
Water bottles are usually made of thermoplastics, which deform on heating. Hence, hot water deforms water bottles.

Also Read

UP Board Notes For Class 8 Science Chapter 4 Materials Metal And Non Metals Science

by

Materials Metal and Non-Metals Chapter In a Nutshell

  • Materials can be classified as metals and non-metals.
  • Metals differ from non-metals in physical and chemical properties.
  • Metals are usually solids except for mercury, which is liquid at room temperature.
  • Metals are hard materials except sodium and potassium which are soft metals that can be easily cut by a knife.
  • Metals are lustrous, sonorous, malleable arid ductile. They conduct heat and electricity.
  • Metals have high melting points except gallium which melts in the hand i.e., at body temperature.
  • Non-metals exist in all three states — solid, liquid and gas. They are brittle, non-lustrous, non-sonorous, poor conductors of heat and electricity.
  • Metals usually combine with oxygen to form metallic oxides, which are basic. These oxides react with water to form bases.
  • Sodium and potassium are the most reactive metals which react readily with oxygen, even at room temperature. That is why they are stored in kerosene oil.
  • Copper reacts with atmospheric oxygen and acquires a green coating of a mixture of copper hydroxide (Cu(OH)j) and copper carbonate (CuCOj) on its surface.
  • Non-metals combine with oxygen and form non-metallic oxides, which are also known as acidic oxides. These oxides react with water to form acids.
  • Phosphorus rapidly bums in the air at room temperature to form phosphorus oxide. It is thus stored in water to avoid its contact with the atmospheric oxygen.
  • Metals react with water depending upon their reactivity to form oxides or hydroxides and hydrogen gas. Non-metals do not react with water.
  • Some very reactive metals like sodium and potassium react violently with cold water.
  • Metals like gold, silver and platinum do rot react even with steam. They are called noble metals.
  • Iron reacts with moisture in the air to form iron oxide. Iron oxide is brownish-red in colour and is called rust
  • Metals react with acids to form corresponding salts with the evolution of hydrogen gas. Non-metals do not react with acids.
  • Most of the metals generally do not react with bases at room temperature. Metals like aluminium and zinc react with strong bases like sodium hydroxide to form complex compounds with the evolution of hydrogen gas.
  • Some of the metals in their increasing order of reactivity are Gold, Silver, Copper, Iron, Zinc, Aluminium, Magnesium, Sodium and Potassium.
  • A reaction in which a more reactive metal displaces a less reactive metal from its solution is called a displacement reaction.
  • Metals and non-metals are used in the industries, kitchens, household items, transport, etc.

Read and Learn More UP Board Notes for Class 8 Science

Materials Metal And Non-Metals Important Terms And Definitions

Malleability: The property of metals by the virtue of which they can be hammered or beaten into thin sheets is known as malleability.
Ductility: The property of metals by the virtue of which they can be drawn to thin wires is known as ductility.
Sonorous: The property of metals to produce a ringing sound when struck by an object is known as sonorous.
Metallic lustre: The property of metals by the virtue of which they shine is called metallic lustre. Metalloids: Materials that show the properties cf both metals and non-metals are called metalloids.

Physical Properties of Metals and Non-Metals

Materials are of two types – metals and non-metals. Metals usually exist in the solid state. They are hard, lustrous, sonorous, malleable, ductile and good conductors of heat and electricity. Metals have high; density and high melting points. Examples of metals are Aluminium, gold, silver, copper, sodium, etc.

Non-metals exist in all three states, liquid and gas. They are soft, brittle, non-lustrous, non-sonorous and poor conductors of heat and electricity. They are neither ductile nor malleable. Examples of non-metals are sulphur, oxygen, bromine, carbon, etc.

Materials Metal and Non-Metals Activity 1

Aim: To show that metals are malleable while non-metals are non-malleable
Procedure:
1. Take a small iron nail, a piece of coal, a piece of thick aluminium wire and a pencil.
2. Hit hard all the materials one by one with a hammer.
3. Note down the observations in the observation table.

Observation:

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Activity 1

Conclusion: Iron and aluminium are malleable while coal and pencil lead are non-malleable materials. This shows that metals are malleable i.e., they can be beaten into thin sheets. Non-metals are non-malleable.

Materials Metal and Non-Metals Activity 2

Aim: To show that metals are good conductors of electricity while non-metals are poor conductors of electricity
Procedure:
1. Make an electric circuit as shown below.
2. Connect the circuits one by one with an iron nail, a piece of sulphur, a piece of coal and a copper wire.
3. Note down your observations in the observation table.

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Activity 2

An electric circuit

Observation:

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Activity 2.

Conclusion: Metals are good conductors of electricity-‘ while non-metals are poor conductors of electricity.

Materials Metal and Non-Metals Objective Type Questions

A. State whether the following statements are true or false.

1. Metal and non-metals have the same physical properties.
2. All non-metals possess lustre.
3. Cooking utensils are made of metals because they/ are good conductors of heat.
4. Mercury is a non-metal found in the solid state.

Answers: 1. False 2. False 3. True 4. False

Materials Metal and Non-Metals Short Answer Type Questions

A. What do you understand by the ductility and malleability of a metal? Give examples of two metals which are both ductile and malleable.

Answer. Ductility is the property of metals by which they can be drawn into thin wires. Examples of ductile metals are copper, silver, etc.
Malleability is the property of metals which means that they can be hammered into thin sheets or foils. Examples of malleable metals are gold, silver, etc.

B. Why aluminium and copper are used for making electrical wires?

Answer. Aluminium and copper are metals. They are duct le and good conductors of electricity. Therefore, aluminium and copper are used for making electrical wires.

Chemical Properties of Metals and Non-Metals

Reaction with oxygen – Metals react with oxygen to form metallic oxides which are basic. Non¬metals react with oxygen to form non-metallic oxides which are acidic.
Reaction with water – Metals react with water to form either oxides or hydroxides and hydrogen gas. Most of the non-metals do not react with water.
Reaction with acids and bases – Metals react with acids to form corresponding salts with the evolution of hydrogen gas. Metals usually do riot react with bases. Most of the iron metals do not react with acids; and bases.
A more reactive metal tends to displace a less reactive metal from its solution. Such a reaction; is known as a displacement reaction.

Materials Metal and Non-Metals Activity 3

Aim: To show that metallic oxides are basic in nature
Procedure:
1. Take a spoonful of rust and dissolve it in a small amount of water.
2. Shake the mixture well and test the solutior with red and blue litmus papers.
3. Observe the colour change of the Irtmus paaer.

Observation: The solution of rust and water changes the colour of red litmus paper to blue. The colour of blue litmus paper does not change.
Conclusion: Metallic oxides are basic in nature.

Materials Metal and Non-Metals Activity 4

Aim: To show that non-metallic oxides are acidic in nature AM Procedure:
1. Take a small amount of sulphur powder in a deflagrating spoon and heat it.
2. As sulphur starts burning introduce the spoon into the gas jar or glass tumbler.
3. Cover the lid and ensure that the gas produced does not escape from the jar.
4. Add a small amount of water it the jar and cover the jar with the lid quickly.
5. Shake the tumbler well and test the solution with red and blue litmus papers.
Observation: When sulphur bums in oxygen, it produces sulphur dioxide. On dissolving this sulphur dioxide in water, sulphurous acid is formed.
so2 +H2O > H2SO,
SJafr.rD’-xde Sjiphjrojt *od
Sulphurous acid changes the colour of blue litmus Daperto red.
Conclusion: Non-metals react with oxygen to form non-metallic oxides. These oxides are acidic in nature. These oxides dissolve in water to form acid.

Materials Metal and Non-Metals Activity 5

Aim: To show the reaction of sodium metal with water
Precaution: The size of the sodium metal should be nearly the size of a wheat grain. A pair of tongs must be used to handle the piece of sodium metal.
Procedure:
1. Take a 250 ml beaker or a glass tumbler and fill it half with water.
2. Cut a small piece of sodium metal carefully.
3. Dry the piece of sodium metal and wrap it in a small piece of cotton.
4. Put the wrapped sodium piece into the bea<er containing water and observe carefully.
5. Touch the beaker after the reaction.
6. Test the solution with red arid blue litmus paper

Observation: Sodium metal reacts vigorously with water and catches fire. The beaker becomes hot during the reaction. The solution turns red Irtmus blue.
Conclusion: Metals like sodium are very reactive. They react vigorously with water ana release a large amount of heat.

Materials Metal and Non-Metals Activity 6

Aim: To show the reaction of metals and non-metals with acids
Precaution: Use a test tube holder to hold the test tube and keep the mouth of the test tube away from your face.
Procedure:
1. Take samples of metals and non-metals as given in the observation table.
2. Put them in separate test tubes and label them as A, B, C, D, E and F.
3. Add 5 ml of dilute hydrochloric acid in each test tube with a dropper.
4. Observe the reaction in the test tubes.
5. If the reaction does not occur in cold solution, warm the test tube.
6. Bring a burning matchstick near the mouth of the test t Jbe.
7. Repeat the activity using dilute sulphuric acid and note the observations in the observation table.

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Activity 6

Conclusion: Metals react with acids to liberate hydrogen gas. The rate of this reaction increases as the temperature of the acid increases. Non-metals do not react with acids.

Materials Metal and Non-Metals Activity 7

Aim: To show the reaction of metals with strong bases
Precaution: Use a plastic spatula to handle the pellets of sodium hydroxide
Procedure:
1. Dissolve 3-4 pellets of sodium hydroxide in 5 ml of water in a test tube.
2. Drop a piece of aluminium foil into the test tube.
3. Bring a burning matchstick near the mouth of the test, tube and observe.

Observation: The burning matchstick extinguishes with a pop sound.
Conclusion: Metals like aluminium react with strong bases to produce hydrogen gas.

Materials Metal and Non-Metals Activity 8

Aim: To show that a more reactive metal can replace a less reactive metal from its solution Procedure:
1. Take five 100 ml beakers and label them as A, B, C, D and E
2. Take 50 ml of water in each beaker and dissolve a teaspoonful of:
Beaker A: Copper Sulphate (CuSO^ and Z’rc granules (Zn)
Beaker B: Copper Sulphate (CuSOJ and Iron nail (Fe)
Beaker C: Zinc Sulphate (ZnSOJ and Copper turnings (Cu)
Beaker D: Iron Sulphate (FeSOJ and Copper turnings (Cu)
Beaker E: Zinc Sulphate (ZnS04) and Iron nail (Fe)
3. Keep the beakers undisturbed for some time and observe the changes in them.

Observation: Beaker A: Zinc replaces copper from the copper sulphate solution and the blue colour of the copper sulphate solution fades. A red powder)’ mass of copper settles at the bottom of the beaker.
Copper Su I phate (C JS04 )+Zi nc (Zn) > Zi nc Sulphate (ZnS04)+Copper (Cu)
CcJou’ets
Beaker B: Iron replaces copper from copper sulphate solution to form iron sulphate. A red powdery mass of copper settles at the bottom of the beaker.
Copper Sulphate (CuS04)+lron(Fe)  iron Sulphate (FeS04) + Copper (Cu)
Bu* colour Rfo
Beaker C: No change is observed in the beaker.
Beaker D: No change is observed in the beaker.
Beaker E: No change is observed in the beaker.
Conclusion: A more reactive metal displaces a less reactive metal from its solution. Such a reaction is called a displacement reaction.

Materials Metal and Non-Metals Objective Type Questions

A. State whether the following statements are true or false.

1. Non-metals vigorously react with water.
2. Metal oxides are basic:n nature.
3. Phosphorus is a non-metal which is stored in water.
4. Hydrogen gas bums with a pop sound.

Answers: 1. False 2. True 3. True 4. True

B. Fill in the blanks.

1. _______and_____are stored in kerosene oil.
2. Iron reacts with oxygen to form____
3. Metals like gold and platinum do not even react with steam. These metals are called____
metals.

Answers: 1. Sodium, potassium 2. Iron oxide 3. Noble

Materials Metal and Non-Metals Short Answer Type Questions

A. Why potassium is not stored in the water?

Answer. Potassium is a reactive metal. It reacts violently with water at room temperature and catches fire. Hence, it is not stored in water but kept in the kerosene oil.

B. Why gold ornaments look new even after several years of use?

Answer. Gold is a non-reactive metal. It does not tarnish. It is unaffected by air, water and acids. Thus, gold ornaments look new even after several years of use.

Uses of Metals and Non-Metals

Answer. Metals like aluminium and copper are used to make electrical wires, iron is used to construct buildings and bridges, aluminium, iron and copper are used in utensils, tools and machinery, gold and platinum are used to make jewellery, magnesium is used to make fireworks, etc.
Non-metals like oxygen is essential for respiration in living beings, hydrogen is used as a fuel, diamond is a form of carbon used as a gemstone, iodine is used as an antiseptic, nitrogen is used to preserve food, chlorine is used for water purification, etc.

Materials Metal and Non-Metals Objective Type Questions

A. Fill in the blanks.

1. _____is a form of carbon used as a gemstone.
2. Food is wrapped in foils made up of______
3.______ is a non-metal used in the purification of water.

Answers: 1. Diamond 2. Aluminium 3. Chlorine

Materials Metal and Non-Metals Long Answer Type Questions

A. List two uses of metals and non-metals.

Two uses of metals are:
1. Metals like iron are used in the construction of buildings and bridges.
2. Metals like gold and platinum are used for making jewellery.
Two uses of non-metals are:
1. Oxygen is essential for respiration in living beings.
2. Nitrogen is used to preserve food. It is a nutrient required by the plants to grow.

Materials Metal and Non-Metals Textbook Exercises

Question 1. Which of the following can be beaten into thin sheets?

  1. Zinc
  2. Phosphorus
  3. SulphurAnswers. The material which can be beaten into thin sheets is (1) Zinc

Question 2. Which of the following statements is correct?

  1. All metals are ductile.
  2. All non-metals are ductile.
  3. Generally, metals are ductile.
  4. Some non-metals are ductile.

Answers. The correct statement is (3) Generally, metals are ductile.

Question 3. Fill in the blanks.

  1. Phosphorus is a very____ non-metal
  2. Metals are_____conductors of heat and
  3. Iron is_____reactive than copper.
  4. Metals react with acids to produce_______gas.

Answers: (1) Reactive (1) Good, electricity (3) More (4) Hydrogen

Question 4. Mark if the statement is true and ‘P if it is false.

  1. (Generally, non-metals react with acids.
  2. Sodium is a very reactive metal.
  3. Copper displaces zinc from the zinc sulphate solution.
  4. Coal can be drawn into wires.

Answers: (1) F (2) T (3) F (4) F

Question 5. Some properties are listed in the following Table. Distinguish between metals and non-metals based on these properties.

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Metals And Non-metals

Question 6. Give reasons for the following.

  1. Aluminium foils are used to wrap food items.
  2. Immersion rods for heating liquids are made up of metallic substances.
  3. Copper cannot displace zinc from its salt solution.
  4. (Sodium and potassium are stored in kerosene.

Answers.

  1. Aluminium foils are used to wrap food items because aluminium is malleable and less reactive to air and water.
  2. Immersion rods used for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity.
  3. Only a more reactive metal can displace a less reactive metal from its solution. Copper is a less reactive metal than zinc. Therefore, copper cannot displace zinc from its salt solution.
  4. Sodium and potassium are very reactive metals. They react vigorously with water to form oxides or hydroxides. Therefore, they are stored in kerosene oil.

Question 7. Can you store lemon pickles in an aluminium utensil? Explain.

Answer. No, lemon pickles cannot be stored in an aluminium utensil because lemon contains citric acid which reacts with aluminium to produce a salt of aluminium and hydrogen gas. This will spoil the food and make it unfit for eating.

Question 8. Match the substances given in Column A with their

UP Board Notes For Class 8 Science Chapter 4 Materials Metals ANd Non-Metals Science Match The Columns

Question 9. What happens when
(a) Dilute sulphuric acid is poured on a copper plate.
(b) Iron nails are placed in copper sulphate solution? Write word equations of the reactions involved.

Answers.

  1. When sulphuric acid is poured on a copper plate, copper reacts with the acid and produces copper sulphate and hydrogen gas.
    Copper + Sulphuric Acid » Copper Sulphate + Hydrogen Gas
  2. Iron is a more reactive metal than copper. When iron nails are placed in the copper sulphate solution, iron displaces copper and forms iron sulphate. This reaction fades the blue colour of the copper sulphate solution and a brown deposit of copper is seen at the bottom of the beaker.
    Iron + Copper Sulphate > Iron Sulphate + Copper


Question 10. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas?
(b) Write down word equations of all the reactions taking place in this process.

Answers.

  1. Saloni can find the nature of the gas by adding few drops of water in the test tube and testing the solution with a red and a blue litmus paper. The blue litmus paper will turn red while the red litmus paper will show no change. This shows that the gas is acidic in nature.
  2. ‘When a charcoal is burnt, it reacts with oxygen to form an acidic oxide called carbon dioxide.
    Charcoal + Oxygen –» Carbon Dioxide
    Carbon dioxide released on burning charcoal reacts with water to form carbonic acid.
    Carbon Dioxide + Wa: er –»Carbonic Acid

Question 11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?

Answers. Jewellers usually use a strong acidic solution to polish the gold jewellery. When the gold is dipped in the acidic solution, it reacts with the acid. A small amount of the gold dissolves in the acid from the outer layer of the jewellery. Thus, there is a slight loss in the weight of the jeweller)

Materials Metal and Non-Metals Hots corner

A. based on the reactions given below, indicate the most reactive metal and the least reactive metal out of zinc, copper and iron.
                   Copper Sulphate + Iron⇒ Iron Sulphate + Copper
                        Iron Sulphate + Zinc ⇒ Zinc Sulphate + Iron

Answers. In the first reaction, iron displaces copper from the copper sulphate solution, therefore, iron is more reactive than copper. In the second reaction, zinc displaces iron from iron sulphate solution, therefore, zinc is more reactive than iron. Therefore, zinc is the most reactive metal and copper is the least reactive metal.

B.Why is graphite not used for making electrical wires?

Answers. Graphite is a form of a carbon which is a non-metal. It is brittle and non-ductile. It is a poor conductor of heat and electricity. Therefore, it can not be used for making electrical wires.

Materials Metal and Non-Metals Practice Exercises

Objective Type Questions

A. Fill in the blanks.

1. Metals exist in _____state.
2. ______foils are used to decorate sweets.
3. Metals produce a ringing sound when struck by something. This shows that metals are_____
4. _______is a non-metal used in the pencil lead.
5. Non-metallic oxides are_______ in nature.

Answers: I. Solid 2. Silver 3. Sonorous 4. Graphite 5. Acidic

B. Answer the following questions in one word.

1. Name a metal that can be cut by using a knife.
2. Name a metal which melts at body temperature.
3. Name a metal which is liquid at room temperature.
4. Name a metal which does not react with water, air or acid.
5. Name a non-metal used for making antiseptics.
6. Name a non-metal which is found in the gaseous state.

Answers: 1. Sodium 2. Gallium 3. Mercury 4. Gold 5. Iodine 6. Oxygen

Materials Metal and Non-Metals Short Answer Type Questions

A. Why phosphorus is stored in water?

Answers. Phosphorus reacts rapidly with oxygen present n air and catches f re. It is, therefore, stored in water to avoid its contact with the atmospheric oxygen.

B. What is the difference in the reaction of oxygen with metals and non-metals? Write their word equation.

Answers.

Metals react with oxygen to form metallic oxides which are basic in nature. These oxides dissolve in water to form bases.
Metals + Oxygen > Metallic Oxide
Non-Metals react with oxygen to form non-metallic oxides which are acidic in nature. These oxides dissolve in water to form acids.
Non-metals + Oxygen » Non-Metalic Oxide

Materials Metal and Non-Metals Long Answer Type Questions

A. Magnesium ribbon burns with a dazzling white flame and forms a white powdered ash. This ash is dissolved in water and tested with a red and blue litmus paper.
Answer the following questions:

  1. What is the white ash formed after burning the magnesium ribbon?
  2. Write the word equation of the reaction that takes place when magnesium ribbon is burnt.
  3. What happens when the white ash is dissolved in water? Give the word equation.
  4. (Give one use of magnesium.

Answers.

  1. The white ash formed after burning the magnesium ribbon is magnesium oxide.
  2. Magnesium + Oxygen » Magnesium Oxide
  3. When the white ash is dissolved in water, magnesium hydroxide is formed.
    Magnesium Oxide + Water > Magnesium Hydroxide
  4. Magnesium is used in fireworks.

 

Also Read

UP Board Notes For Class 8 Science Chapter 9 Reproduction In Animals

by

Reproduction In Animals Chapter Objectives

  • Reproduction is essential for the continuation of a species.
  • Gametes are the reproductive cells produced by the sex organs.
  • The male reproductive system in animals includes a pair of testes, a pair of sperm ducts, and a penis.
  • Testes produce sperm or the male gametes.
  • A sperm is a very small, single-celled structure with all the usual cell components. It consists of a head, a middle piece, and a tail.
  • The female reproductive system in animals consists of a pair of ovaries, oviducts or fallopian tubes, uterus and vagina.
  • Each ovary produces one mature ovum or egg every month and discharges it into the oviduct.
  • The uterus is a hollow. muscular, pear-shaped organ in which the embryo develops.
  • Asexual and sexual reproduction are the two modes of reproduction in animals.
  • In asexual reproduction, a new individual is formed from the cell of a single parent.
  • Binary fission and budding are the two methods of asexual reproduction.
  • In binary fission, a fully-grown cell divides to produce two new cells. Amoeba reproduces by binary fission.
  • In budding new individuals are formed as an outgrowth from a single parent. These extensions are called buds.
  • A fully matured bud detaches itself from the parent body and becomes a new individual capable of existing independently.
  • Sexual reproduction involves the fusion of male and female gametes. Human beings and other
    mammals reproduce sexually.
  • Fertilisation is the fusion of sperm and ovum to form a fertilised egg or zygote. It is the first step in the process of reproduction.
  • When male and female gametes fuse inside the female’s body as in human beings, dogs, cats, etc, the fertilisation is referred to as internal fertilisation.
  • External fertilisation occurs when male and female gametes combine outside the female’s body.
  • Viviparous animals give birth to young ones. Human beings, dogs, cats, etc., are viviparous animals.
  • Oviparous animals lay eggs, which later develop into young ones. Frogs, birds, etc., are examples of oviparous animals
  • Metamorphosis is the transformation of a larva into an adult through a series of changes.
  • Larva is an animal’s early form having features, different from the adult.

Read and Learn More UP Board Notes for Class 8 Science

Reproduction In Animals Important Terms and Definitions

Cloning: It is the process of production of an exact copy of an organism.
Foetus: It is that stage of the embryo in which all the body parts can be identified.
In vitro fertilization (IVF): It is a technique in which the egg is fertilised outside the body of the female.
It is used when women are not able to conceive due to blockage of oviducts.

Reproductive Organs

Answers: The male reproductive organs consist of a pair of testes, a pair of sperm ducts and a penis. Testes produce nearly millions of sperm. The male gamete or the sperm is single-celled and has a head, a middle piece and a tail. Ovaries, oviducts or fallopian tubes, a uterus and vagina are the main female reproductive organs. The female gamete or the ovum is produced by the ovaries. When a male gamete fertilises a female gamete, it results in the formation of a zygote.

Reproduction In Animals Objective Type Questions

A. State whether the following statements are true or false.

  1. The embryo gets embedded in the fallopian tube.
  2. Sperms are single-celled.
  3. The male reproductive system consists of a pair of testes, two sperm ducts and a penis.
  4. The zygote divides repeatedly to form a ball of cells.
  5. The egg of a human female contains a large amount of yolk.

Answers:

  1. False
  2. True
  3. True
  4. True
  5. False

B. Multiple Choice Questions.

1. Which of the following is not a male reproductive organ?

  1. Penis
  2. Testes
  3. Sperm ducts
  4. Fallopian tubes

Answers: 4) Fallopian tubes

2. Which of the following is referred to as the beginning of an individual?

  1. Sperm
  2. Male gametes
  3. Zygote
  4. Embryo

Answers: 3) Zygote

3. Which of the following statements is true for fertilisation?

  1. Meeting of an egg and a sperm cell
  2. Fusion of the male and female gametes
  3. Results in carrying of inherited characters to the next generation
  4. All of these

Answers: 4) All of these

4. Which one of the following is known as a sex cell?

  1. Zygote
  2. Gamete
  3. Embryo
  4. Foetus

Answers: 2) Gamete

C. Fill in the Blanks.

  1. A male gamete is known as a/an______ and a female gamete is known as a/an
  2. The stage of a developing embryo at which all body parts become identifiable is known as a______
  3. A multicellular animal starts its life as a single cell known as a_______
  4. In human beings, the embryo develops inside the________of the female.
  5. In human beings, fertilisation takes place in the

Answers:

  1. Sperm, ovum
  2. Foetus
  3. Zygote
  4. Uterus
  5.  Fallopian tubes

Reproduction In Animals Short Answer Type Questions

A. Describe the female reproductive system in brief.

Answers: The female reproductive system consists of ovaries, oviducts or fallopian tubes and the uterus. The female gametes called the ova or eggs, are produced by the ovaries. The ovaries discharge one mature, single-celled egg into the oviduct of human females every month.

B. What organs in human beings produce gametes?

Answers: In human beings, the male gamete or the sperm is produced by a pair of testes and the female
gamete or the ovum is produced by a pair of ovaries.

Modes of Reproduction

Answers: Animals have two modes of reproduction: sexual and asexual. When male and female gametes combine to form a zygote, it is known as sexual reproduction. The zygote divides repeatedly to form an embryo, which embeds itself in the wall of the uterus and develops into a foetus. The different stages of a frog starting from the egg to the adult are:
Egg → Larva →→ Adult
When organisms are reproduced by a single parent, it is known as asexual reproduction. The two methods of asexual reproduction are budding and binary fission. Hydra reproduces through budding. Single-celled organisms such as Amoeba reproduce asexually through binary fission.

Reproduction In Animals Activity 1

Aim: To observe the colour and size of frog’s eggs
Procedure:
1. Visit a pond during the rainy or spring season.
2. Notice the things floating in it.
Observation: Dull-white, bunches of frog eggs can be seen floating on the surface of the water.
Conclusion:
1. Frogs move to ponds in the rainy or spring season and female frogs lay hundreds of eggs in water.
2. These eggs are dull white, are not covered by a shell and are held together by a layer of jelly which also protects them.

Reproduction In Animals Activity 2

Aim: To observe the eggs of frogs, lizards, butterflies moths, hens crows or any other bird
Procedure:
1. Visit a garden near your home or school.
2. Look for the eggs of frogs, butterflies, lizards and crows.
3. Visit a local shop to look at the eggs of a hen.
4. Observe the eggs and note down the differences among them.
5. Note the size, colour and shape of each type of egg.
6. Make drawings of these eggs in your notebook.

Observation: The eggs of each organism are different in shape and size.
Conclusion:
1. Animals such as hens, frogs, etc., lay eggs outside their bodies. Such animals are called oviparous
animals.
2. Animals such as cows, dogs, etc., do not lay eggs but give birth to young ones. Such animals are called viviparous animals.

Reproduction In Animals Activity 3

Aim: To study budding in Hydra
Material Required: Permanent slides of Hydra and a microscope
Procedure:
1. Observe the permanent slides of Hydra under the microscope.
2. Observe them first under the low-power lens and then under the high-power.
3. Look for bulb-like projections from the parent body and count them.
4. Observe the size of different projections or buds.
5. Draw a rough sketch of what you observe.

UP Board Notes For Class 8 Science Chapter 9 Cell Structure And Functions Reproduction In Animals Activty 3

Observation: Each Hydra has one or more than one bud.
A bud is an outgrowth, which develops as cells divide constantly at a particular location.
A fully matured bud detaches itself from the parent body and becomes a new individual capable of
existing independently.
Conclusion: Hydra reproduces asexually through budding.

Reproduction In Animals Objective Type Questions

A. State whether the following statements are true or false.

Answers:

  1. In sexual reproduction, male and female gametes combine to form a zygote.
  2. All animals reproduce through sexual reproduction.
  3. Out of the millions of sperm produced, only one of the sperm fuses with the egg.
  4. Fertilisation occurs inside the body of a cow.
  5. Amoeba reproduces asexually through budding.
  6. Cows and dogs are viviparous animals.

Answers:

  1. True
  2. False
  3. True
  4. True
  5. False
  6. True

B. Multiple Choice Questions.

Question 1. Which of the following animals reproduces through budding?

  1. Rat
  2. Elephant
  3. Human beings
  4. HydraAnswers. 4) Hydra

Question 2. What is the process of formation of an adult frog from the larva called?

  1. Internal fertilisation
  2. External fertilisation
  3. Sexual reproduction
  4. MetamorphosisAnswers. 4) Metamorphosis

Question 3. What is the stage between the egg and the larva in a butterfly called?

  1. Pupa
  2. Adult
  3. Caterpillar
  4. None of these answers. 1) Pupa

Question 4. By which stage are the parts of an embryo identifiable?

  1. Adult
  2. Larva
  3. Pupa
  4. FoetusAnswers. 4)Foetus

Question 5. What term is given to an organism that has both the male and the female sex organs?

  1. Unisexual
  2. Multisexual
  3. Hermaphrodite
  4. Asexual

Answers: 3) Hermaphrodite

C. Fill in the blanks.

  1. Amoeba reproduces asexually through____
  2. Budding is a form of______reproduction.
  3. External fertilisation occurs in_______
  4. Gametes are produced in_____reproduction

Answer: 1. Binary fission 2. Asexual

Reproduction In Animals Short Answer Type Questions

A. What is binary fission?

Answers: It is a method of asexual reproduction and is common in single-celled organisms such as Amoeba. In this method, a fully grown parent cell divides itself to produce two daughter cells. Each daughter cell gives rise to a new individual.

B. What is the difference between unisexual organisms and hermaphrodites?

Answers: Unisexual organisms are those in which male and female gametes are produced by separate individuals Hermaphrodites are organisms in which the same individual produces both the male and female gametes.

C. How are chicks born?

Answers: Internal fertilisation takes place in hens but they do not give birth to young ones. The zygote moves down the oviducts and protective layers are formed around it. One of these protective layers is the hard shell. The hen lays the eggs once this hard shell is formed and sits on them to provide them with warmth. In three weeks, the embryo within this shell develops into a chick. Once the chick is fully developed it breaks open the eggshell and comes out.

Reproduction In Animals Textbook exercises

Question 1. Explain the importance of reproduction in organisms.

Answers: Reproduction is an important biological process because it ensures the existence and continuity of a species. It also helps in the transmission of heredity from one generation to another.

Question 2. Describe the process of fertilisation in human beings.

Answers: The first step in the process of reproduction in human beings is the fusion of a sperm and an ovum or egg. Millions of sperm are released into the female’s body out of which only one of the sperm may fuse with the egg. Such fusion of the egg and the sperm is called fertilisation. During fertilisation, the nucleus of the sperm and the egg fuse to form a single nucleus. The zygote thus formed is the beginning of a new individual.

Question 3. Choose the most appropriate answer.

(a) Internal fertilisation occurs

  1. in the female body
  2. outside the female body
  3. in the male body
  4. outside the male body

Answer: (1) in the female body

(b) A tadpole develops into an adult frog by the process of

  1. Fertilisation
  2. Metamorphosis
  3. Embedding
  4. Budding

Answer: (2) Metamorphosis

(c) The number of nuclei present in a zygote is

  1. None
  2. One
  3. Two
  4. Four

Answer: (2) One

Question 4. Indicate whether the following statements are True (T) or False (F).

Answers:

  1. Oviparous animals give birth to young ones.
  2. Each sperm is a single cell.
  3.  External fertilisation takes place in frogs.
  4. A new human individual develops from a cell called a gamete.
  5. An egg laid after fertilisation is made up of a single cell.
  6. Amoeba reproduces by budding.
  7. Fertilisation is necessary even in asexual reproduction.
  8. Binary fission is a method of asexual reproduction.
  9. A zygote is formed as a result of fertilisation.
  10. An embryo is made up of a single cell.

Answers:

  1. (a) False
  2. (g) False
  3. (b) True
  4. (h) True
  5. (d) False
  6. (i) False
  7. (iv) Budding
  8. (iv) Four
  9. (e) True
  10. (f) False

Question 5. Give two differences between a zygote and a foetus. It is unicellular.

Zygote

It is formed by the fusion of the male and female gametes.

Foetus

It is formed by the repeated divisions of the zygote. It is multicellular.

Question 6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.

Answers: The type of reproduction in which only a single parent is involved is called asexual reproduction.
Following are the two methods of asexual reproduction in animals:

  1. Binary fission: Binary fission involves almost an equal division of the parent cell into two daughter cells, each of which grows into a new individual. This method of reproduction occurs regularly among protozoa like Amoeba, Paramecium, etc.
  2. (Budding: Budding is the form of asexual reproduction in which a new individual arises from a bud. The bud develops on the parent body, gets detached and grows into a separate individual, for example as in Hydra.

UP Board Notes For Class 8 Science Chapter 9 Cell Structure And Functions Two Methods Of Asexual Reproduction In Animals.

Question 7. In which female reproductive organ does the embryo get embedded?

The embryo gets embedded in the walls of the uterus.

8. What is metamorphosis? Give examples.

Metamorphosis is the drastic change that takes place during the development of an animal from the larval to the adult stage.

UP Board Notes For Class 8 Science Chapter 9 Cell Structure And Functions What Is Metamorphosis

The above figure shows three stages in the development of a frog. egg, tadpole or larva and the adult frog.
The tadpole or larva is different from its adult form. Tadpole has gills for respiration because it lives in water. During metamorphosis, the body of the tadpole changes to become an adult frog. For example, the gills are replaced by the lungs. Another animal in which metamorphosis takes
place is the silkworm.

Question 9. Differentiate between internal fertilisation and external fertilisation.

UP Board Notes For Class 8 Science Chapter 9 Cell Structure And Functions Differentiate between internal fertilisation and external fertilisation.

Question 10. Complete the crossword puzzle using the hints given below.

Across:

  1. The process of fusion of gametes.
  2. The type of fertilisation in hens.
  3. The term is used for bulges observed on the sides of the body of Hydra.
  4. Eggs are produced here.

Down:

  1. Sperms are produced in these male reproductive organs.
  2. Another term for the fertilised egg.
  3. These animals lay eggs.
  4. A type of fission in Amoeba.

Across:

  1. Fertilisation
  2. Internal
  3. Buds
  4. Ovary

Down:

  1. Testis
  2. Zygote
  3. Oviparous
  4. Binary

External Fertilisation
The fusion of male and female gametes takes
place outside the female body.
Both the males and females discharge their
gametes in water.
Development of embryo occurs outside the
female body.
A few examples are frogs, fish, starfish, etc.

Reproduction In Animals Hots corner

A. Why do aquatic animals like frogs and fish that undergo external fertilisation produce a large number of sperm and eggs?

Answers: The eggs and sperm of aquatic animals get exposed to water movement, wind and rainfall. There are other animals present in water, which feed upon these eggs. All these factors reduce the chances of fertilisation of the eggs. Thus, the production of a large number of eggs and sperm is necessary to ensure the fertilisation of at least a few of them.

Reproduction In Animals Practice Exercise Objective Type Questions

A. Circle the odd one out.

  1. Ovary, Oviducts, Uterus, Testes
  2. Testes, Sperm ducts, Penis, Vagina
  3. Fertilisation, Embryo development, Metamorphosis, Budding

Answers: 1. Testes 2. Vagina 3. Budding

B. Give one word for the following.

  1. The process by which a tadpole develops into an adult frog
  2. The animals that lay eggs
  3. Mode of reproduction in which both parents are needed
  4. The cell formed due to the fusion of male and female gametes
  5. Animals which lay eggs

Answers:

  1. Metamorphosis
  2. Oviparous
  3. Sexual
  4. Zygote
  5. Oviparous

C. State whether the following statements are true or false.

  1. Viviparous animals give birth to young ones.
  2. Foetus is another name for the unfertilised egg.
  3. The first mammal to be cloned was a cow.
  4. Reproductive cells produced by the male sex organs are called ova.

Answers:

  1. True
  2. False
  3. False
  4. False

Reproduction In Animals Short Answer Type Questions

A. What is a zygote?

Answers: Zygote is formed from the fusion of the male and the female gametes. It is the first cell of the organism and hence, is also referred to as the beginning of an individual.

B. Sometimes identical twins are born to human beings. What do you think is the reason behind this?

Answers: At times, the fertilised egg or the zygote splits into two and each of these develops into two individuals. The two resulting offspring are identical twins.

C. Why do several animals like dogs, cats, etc., always produce so many young ones at a time?

Answers: In animals like dogs, cats, etc., instead of one egg several eggs are fertilised. Each fertilised egg develops into a zygote. Hence, many young ones are produced at a time.

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