NEET Biology The Living World Notes

The Living World

Living Being Introduction: Life is a precious gift of nature. Life can be explained by its way of working. This universe has living and non-living entities. Viruses are the connecting link between living and non-living.

The Nature around us is full of living and non-living objects. Now it is essential to know the difference between living and non-living. Living organisms have self-replicating, self-evolving, and self-regulating systems, capable of responding to external stimuli.

After having an idea about living being developed in our mind. Of course, the objects by themselves exhibiting birth, death, life span, consciousness, growth, and metabolism are known as living beings.

Characteristics Of Living Being

All Living Beings Share Certain Characteristics Which Are Listed Below:

1. Growth
2. Reproduction
3. Metabolism
4. Consciousness
5. Respiration
6. Cellular organization

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1. Growth: The numerical and structural enhancement in the object is termed growth. It can be explained on the basis of catabolism and anabolism.
   • Anabolism > Catabolism = Growth
   • Catabolism > Anabolism = Degrowth
   • Although growth is also noticed in non-living objects, but this type of growth is extrinsic (by the accumulation of materials on the surface).
     1. Growth is not a defining property of a living being because a dead organism does not grow.
     2. The growth of non-living is extrinsic and of living beings is intrinsic.
     3. The growth of plants is indefinite and that of animals is definite.
2. Reproduction: The ability to produce a new individual is called reproduction. New individuals are similar to their parents. Reproduction may be of asexual or sexual type.  In unicellular organisms (procaryotes and eucaryotes), reproduction and growth are the same phenomenon. There are many living organisms where reproduction is altogether absent, for example, mules, and bee workers.
   1. Reproduction is not the defining property of a living being.
   2. No non-living object is capable of reproduction.
3. Metabolism: Metabolism is the combination of anabolism and catabolism. There are thousands of metabolic reactions occurring in living beings. Metabolic reactions can be demonstrated in vitro (in a cell-free system).
   1. An isolated metabolic reaction outside the body is neither living nor non-living.
   2. Metabolic reactions in in-vitro are non-living.
   3. Metabolic reactions in in-vivo (inside the cell) are living, hence cellular organization is the defining property of life.
4. Consciousness: We may confuse consciousness with awareness and sensitivness. All organisms from procaryotes to eucaryotes sense their surroundings and respond. A man is lying in a coma on a life support system. The heart and lungs are replaced by machines. Such a person has the least chance to come back to normal life. Is this patient living or non-living? Of course, this patient is living.
   1. Consciousness is the defining property of living organisms.
   2. A requisite amount of consciousness is required to be called a living being.
   3. Only humans have self-consciousness.

Diversity In The Living World

Currently, about 1.7 million species of animals and plants have been given scientific names, 1.2 million animals, and 0.5 million plants. Amongst animals, insects form the largest group with 1,025,000 species. Existing living species are the outcome of about 3.5 billion years of evolutionary process on this earth. Nearly 15,000 new species are discovered every year.

Since it is nearly impossible to study all the living organ¬isms, it is necessary to devise some means to make this possible. This can be done by proper classification of the organisms.

Taxonomy And Systematics

Taxonomy: It is the branch of biology dealing with the identification, nomenclature, and classification of living organisms. It deals with rules and principles of classification. The term “taxonomy” was coined by A.P. de Candolle. Carolus Linnaeus is considered as the father of taxonomy.

Systematics: It is the study of the diversity of organisms and all their comparative and evolutionary relationships, based on comparative anatomy, comparative ecology, comparative physiology, and comparative biochemistry (G. Simpson, 1961) ‘The word “systematics” was first used by Carolus Linnaeus.

Nomenclature

There is a need to standardize the naming of living organisms such that a particular organism is known by the same name all over the world. This process is called nomenclature. Nomenclature can be done in the following ways:

• Vernacular Name: The name is given in the local language, if varies from place to place, even within a country.
• Scientific Name: To give a universal name to an organism on the basis of definite rules and criteria.

Polynomial Nomenclature: Using many words for a name is called a polynomial system of nomenclature. The organism’s name consists of a series of Latin descriptive words. Such names became lengthy and difficult to learn, for example, Caryophyllum: Caryophyllum saxatilisfoils gramineus umbellatis corymbis.

Trinomial Nomenclature: Using three words for a name is called a trinomial system of nomenclature. It was given by Lamarck. It consists of three words, i.e., genus, species, sub-species (in zoological literature), or variety (in botanical literature). For example, Corvus splendens (Indian crow), and Brassica oleracea capitata (cabbage).

Binomial Nomenclature

• Using two words, i.e., genus and species, is called binomial system of nomenclature. Swedish naturalist Carolus Linnaeus established binomial nomenclature, though it was first proposed by Caspar Bauhin in his book Pinax.
• Linnaeus gave some principles of the binomial nomencla¬ture in Philosophia Botanica (1751), but the nomenclature was used first in Species Plantarum (1753) where names and descriptions of 5900 species of plants were given. Later he published Systema Naturae (1758) where 4326 species of animals were described.
• Scientific names have been standardized through the International Code of Botanical Nomenclature (ICBN, 1961) and the International Code of Zoological Nomenclature (ICZN, 1964).
• The International Code for Nomenclature of Bacteria (ICNB) and International Code of Nomenclature for Cultivated Plants (IC- NCP) are currently being developed from the most recent rules of virus classification and nomenclature by the International Committee for the Taxonomy of Viruses (ICTV).
• The codes are established and improved upon at the International Botanical and Zoological Congress held from time to time.

Rules For Blonomial Nomenclature

1. A scientific name consists of two words in Latin is are Latinized if derived from any other language.
2. The first word is genus and starts with a capital letter and the second name is species that starts with a small letter.
3. Both names are printed in italics or arc underlined separately if handwritten.
4. The name of the author is written in abbreviated form after the species name and it is printed in Roman and never underlined.
5. All these three words (generic epithet, specific epithet, author citation) collectively form a binomial epithet, for example, Mangifera indica Linn.
6. If there are two or more words in the species name, a hyphan is put between these words and constitutes compound compound-specific name, for example, Hibiscus rosasinensis.
7. No names are recognized prior to those used by Linnaeus in 1758 in the 10th edition of Sysiana Naturae.
8. In case two or more names are given, the oldest, i.e., the name given first, is recognized as a valid name and all other names are called synonyms.
9. Rule Of Priority: It is the most important of all rules of ICBN.
10. The names with the same genus and species name are called (autonyms, for example, Rattus rattus. These are not recognized by botanists. Names with the same species and subspecies names are called autonyms, for example, Corvus spleens specimens. One name for two different plants are called homonym, for example, Primus dulcis (almond and plum).

Type Specimen: The type method or application is a legal device to provide the correct name for a taxon.

• Holotype: Nomenclature type.
• Isotype: Duplicate of holotype.
• Paratype: Any other specimen described along with the holotype.
• Syntype: Any one of the two or more specimens cited by the author when there is no holotype.
• Lectotype: Specimen selected from original material to serve as nomenclature type where there is no holotype.
• Neotype: New nomenclatural type when the original material is missing.

Taxonomic Hierarchy

It is a series of different classification ranks that are placed in descending or ascending order.

• It was first given by Linnaeus who introduced five categories in the taxonomic hierarchy, viz., class, order, genus, species, and variety. Later on three more categories, viz., kingdom, division or phylum, and family were added and variety was discarded to make a hierarchy of seven obligate categories, viz.
  • Order
  • Family
  • Genus
  • Species
• Intermediate categories are written with prefixes “super” and “sub,” for example, superclass, and subclass. The tribe is an intermediate category between a subfamily and a genus.
• The higher the category, the higher the number of organisms in it, and fewer will be the number of common characters.
• In accordance with the International Code of Botanical Nomenclature, the names of different categories must end in the standard endings (suffixes) given below:
  • Division: phyta
  • Class: phyceae or opsida or ae
  • Order: ales
  • Family: aceae
  • Tribe: eae
  • Suffixes Used In The Animal Kingdom Are:
    • Family: idea
    • Tribe: ini
• A taxon is a taxonomic group of real organisms assigned to a category. The category represents rank/level in a hierarchy.

Organisms With Their Taxonomic Categories

Concepts Of Species

1. Static Concept Of Species Was Given By Linnaeus: species is fixed and immutable.
2. Dynamic Concept Of Species Was Given By Lamarck: species is mutable and dynamic.
3. Typological Concept Of Species: It is the most simple and widely held species concept. According to this concept, there is an ideal pattern (type) for each species. Individuals of a species match the type as closely as possible. Variations, if any, are due to imperfections of the physical world. Such a concept is said to be typological because it conceives an ideal type of body for each species.
4. Nominalistic Concept Of Species: Species have no existence, only the individuals do so.
5. Biological Concept Of Species (Given By Ernst Mayr): Species is the fundamental unit of classification. A species is a group of organisms
   • Which are closely related (structurally and functionally), sharing a common gene pool, and
   • Which can interbreed freely and produce fertile offspring in a natural environment.

Concept Of Species Exception:

Types Of Species

1. Morphospeoies: Species erected on the basis of morphological characters only.
2. Taxonomic Species: Species having a definite binomial name.
3. Sibling Species: True species which do not interbreed but are otherwise. Difficult to separate on the basis of morphological characters alone. For example, Drosophila pseudoobscura and D. persimilis
4. Allopatric Species: Species having exclusive areas of geographic distribution.
5. Sympatric Species: Species having overlapping areas of geographic distribution.
6. Parapatric Species: Species with adjacent geographic ranges meeting in a very narrow zone of overlap.
7. Neontological Species: Living species.
8. Allochronic Species: Species belonging to different time period.
9. Synchronic Species: Species belonging to the same period of time.
10. Polytypic Species: Species with two or more subspecies.

Taxonomical Aids

The laboratory and field studies are important for the identification of various species and their placement in taxonomical hierarchy. The information thus gathered about the species needs to be stored for future use. These are the taxonomical aids that help in taxonomic studies.

Herbaria: Herbarium is defined as a place where plant material is preserved using various techniques and arranged in the sequence of an accepted classification system.

Usually, the preservation of plants involves drying and pressing the plant material. However, those plants that are either succulent or unsuitable for pressing and drying techniques arc fixed in suitable liquid preservation such as 2-5% formaldehyde, acetic, acid, and alcohol or FAA.

The herbarium techniques involve several steps such as collection, drying, poisoning, mounting, stitching, labeling, and deposition.

1. Tools For Collection Of Plants: Digger for digging roots, scissor for cutting twigs, knife for woody twigs, and a pole with a hook for collecting parts of tall trees. The collections are kept inside a metallic vasculum to avoid loss of moisture and distortions by drying and shriveling up. Polythene bags are also used for this purpose.
2. Dried specimens are poisoned by using chemicals such as 0.1% solution of HgCl₂ (corrosive sublimate).
3. International size of herbarium is 41 x 29 cm.
4. Preserved specimens are sprayed with repellents or disinfectants such as DDT powder or copper sulfate solution at intervals of 4-6 months to keep off small insects such as silverfish.

Functions Of Herbarium: The two primary functions of herbarium are accurate identification and alpha taxonomic research. The secondary functions include closer interaction between the student of general systematics and the herbarium. The important functions of a national herbarium are listed below.

• To preserve plant wealth including type material and palaeobotanical collections.
• To carry out the exchange and loan of preserved plant material for research, exhibitions, etc.
• To carry out research programs of fundamental and applied value.
• To fulfill public needs by supplying materials and scientific information about plants, by arranging training courses, exhibitions, etc.

Classification Of Herbaria

1. Major or national herbaria cover the flora of the world and serve the purpose of research as well as identification.
2. Minor herbaria include smaller herbaria such as regional herbaria (set up by the government), local herbaria (serve the purpose of a small area like a district), and college/university herbaria (primarily for teaching and postgraduate research).

A list of important herbaria of the world is given below along with their standard abbreviations and the approximate number of specimens they hold.

1. Royal Botanic Gardens, Kew (K): over 6,000,000
2. British Museum of Natural History (BM): 6,000,000
3. Royal Botanic Garden, Edinburgh (E): 1,500,000 National Herbarium of Victoria, Melbourne, Australia (MEL)
4. Central National Herbarium, Calcutta (CAL): 2,000,000
5. Herbarium of the Forest Research Institute, Dehradun (DD): 300,000
6. Herbarium of the National Botanical Research Institute, Lucknow (LWG): 80,000

Flora Or Manual: The complete listing and description of the plants growing in a particular area are published in flora or manual such as:

1. Flora of British India by J.D. Hooker.
2. Flora of Delhi by J.K. Maheshwari.
3. Flora Indica by William Roxburgh.
4. Flora Simlensis etc.

Botanical Gardens: From the time of Theophrastus (about 380 to 287 BC), gardens have contributed to the science of botany. But there was an impetus to the botanical explorations only in the post-Lennun period. In ancient Indian culture, the cultivation of food and medicinal plants is known from 4000 to 2000 BC. The “Hanging Gardens of Babylon” are amongst the wonders of the ancient world.

During the Middle Ages, from AD 600 to 1600, there was a lapse in the introduction of plants. In the seventeenth century, there was a revival in the interest and by the eighteenth century, most of the famous botanical gardens known today had already been established. There are about 525 botanical gardens in various countries, but only about 125 with documented collections of authenticated taxa. The functions of a botanical garden are:

• Provides records of local flora for monographic work.
• Provides facilities for collections of living plant material for biosystematic studies.
• Supplies seeds and material for botanical investigation.
• Botanical gardens have an aesthetic appeal and attract a large number of visitors for the observation of general plant diversity.

The International Association of Botanical Gardens was established in 1962. This association has published the International Directory of Botanical Gardens (1983).

Some Of The Important Botanical Gardens Are Listed Below:

1. Royal Botanical Garden, Kew, England: It was founded, in 1759 by William Alton but was officially opened in 1841 and was called the “Botanical Capital” of the Hooker was one of its directors. It is famous for its Alpine house, Rose Garden/Arnold house, greenhouse, temperature house, bamboo garden, and lily pond.
   • It is associated with the Jodrell Laboratory of Experimental Taxonomy. It is spread in 200 acres and Kew satellite is spread in 400 acres. It is famous for Acacias, Acer, Rhus, Citrus, Rosa, Primus, and Magnolia. It has a Chelsea Physic Garden for horticulturists. Kew Bulletin and Index Kewensis are the two premier publications of the Kew Garden.
2. Orto Botanico (Padua Gardens), Italy: It is said to be the first botanical garden. It is famous for grasses, alliums, irids, Paeonias, succulents, and hydrophytes.
3. Pisa, Italy: Almost as old as Padua Gardens, it was the first to introduce palaeontological practices for the study of plant fossils. Caesalpino and John Ray have been associated with this garden.
4. Villa Taranto, Italy: It is the most beautiful garden of Italy and is important from a horticultural point of view.
5. Royal Botanical Garden, Edinburgh, Scotland: Founded in 1670, it is the second oldest garden in Great Britain. It is famous for its Rhododendrons, azaleas, and Himalayan alpine plants, a demonstration garden, and a glasshouse. It has the finest rock garden in the world.
6. Botanischer Garten, Berlin: Established in 1646, A.W. Eichler and Adolf Engler are two of its famous directors.
7. Botanical Garden, Uppsala: Founded by O.J. Rudbeck in 1655, Linnaeus succeeded him as director in 1742.
8. Main Botanical Garden, Moscow: Largest botanical garden; spread over an area of 900 acres.

Botanical Gardens Of India

1. The Indian Botanical Garden, Calcutta, India: It was founded in 1787, by Lt. Col. Robert Kyd. It covers an area of 273 acres and contains collections of the world’s tropical plants. It is one of the greatest botanical gardens in the world and one of the first to be established in the tropics.
   • William Roxburgh, “Father of Indian Botany” was its director from 1793 to 1813. It has the largest herbarium in the east and is famous for the great Banyan tree Ficus benghalensis, which is two centuries old, the palm houses, nurseries, and the amazon lily, Victoria amazonica, the plant with the largest leaves. It is now under the control of BSI (Botanical Survey of India).
2. Lloyd Botanical Garden, Darjeeling
3. National Botanical Garden, Lucknow
4. Tamil Nadu Government Garden, Ootacamand
5. Lalbag Gardens, Bangalore
6. Saharanpur Botanical-Gardens, Saharanpur

Special Kinds Of Gardens

1. Arboretum: The main collections are of woody species.
2. Pinetum: Mainly collections of conifers.
3. Orchidarium: A garden containing collections of orchids, for example, National Orchidaria in BSI, Shillong, and Coimbatore.
4. Bambusetum: With the main collection of bamboo

Museums: These have collections of preserved plants and animals for study and reference. These are prepared to preserve algae, fungi, mosses, ferns, and parts of gymnosperms since they cannot be kept in herbaria. These differ from parks because no living object is displayed in museums.

Some Important Museums

1. Natural History Museum, London
2. United States National Museum, Washington
3. National Museum of Natural History (NMNH), Delhi
4. Prince of Wales Museum, Mumbai

Zoological Parks

1. Zoos/zoological gardens (parks) are protected areas or enclosed spaces where live wild animals are kept.
2. Objectives are public exhibitions to understand wildlife, recreation, education, in situ conservation, and breeding of rare fauna.
3. National Zoological Park (Delhi) is one of the finest zoos of Asia.

Keys: The scheme for the identification of plants and animals is known as a key. These are based on the contrasting characters (couplet). Being analytical in nature, a key has been completed with two leads. These are generally of two types:

1. Indented Or Yoked Key: It has the sequence of choices between two or more statements of characters of species.
2. Bracketed Key: Bracketed keys are the most popular keys. The pairs of contrasting characters are used for identification and are given in numbers in brackets.

 

The Living World Assertion Reasoning Questions And Answers

In the following questions, an Assertion (A) is followed by a corresponding Reason (R). Mark the correct answer.

1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
2. If both Assertion and Reason are true, but the Reason is not the correct explanation of the Assertion.
3. If Assertion is true, but Reason is false.
4. If both Assertion and Reason are false.

Question 1.

Assertion: Members of a species are reproductively isolated from others belonging to other species.

Reason: Species is the basic taxonomic category.

Answer: 2. If both Assertion and Reason are true, but the Reason is not the correct explanation of the Assertion.

Question 2.

Assertion: Rosa indica is a taxon and species is its category.

Reason: Taxon represents real biological objects while category is an abstract term representing a rank in classification.

Answer: 1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

Question 3.

Assertion: A group of closely related families form an order.

Reason: The families of an order show close resem¬blance in certain fundamental features and also in evolutionary trends.

Answer: 1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

Question 4.

Assertion: The biological concept of species is based on reproductive isolation.

Reason: Tigon is the interspecific sterile hybrid produced in captive conditions.

Answer: 3. If Assertion is true, but Reason is false.

Question 5.

Assertion: Synonyms are the most important of all rules of ICBN.

Reason: Out of the two or more scientific names given to the organism, the oldest lame is recognized as a valid name and other names as synonyms.

Answer: 1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

Question 6.

Assertion: Arboretum is the cx-situ conservation strategy of plants.

Reason: It is a special kind of garden with a main collection of herbs and shrubs.

Answer: 3. If Assertion is true, but Reason is false.

Question 7.

Assertion: Two plants A and B are treated as two taxonomic species.

Reason: Both A and B are different in correlated morphological characters.

Answer: 1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

Question 8.

Assertion: Species is a genetically closed system.

Reason: Because reproductive isolation constitutes the most important boundary between different species.

Answer: 1. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

Question 9.

Assertion: Scientific names have been standardized through ICBN.

Reason:  The first international botanical congress was held in Paris in 1967.

Answer: 3. If Assertion is true, but Reason is false.

Question 10.

Assertion: Dried specimens are poisoned by HgCl₂.

Reason: It prevents the specimen from moisture.

Answer: 3. If Assertion is true, but Reason is false.