Chapter 1 Biology
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Diversity in the living world
1-8. Biology is the science of life forms and living processes.
Living world comprises an amazing diversity of living organisms. Early man could easily perceive the difference between inanimate matter and living organisms.
Early man defined some of the inanimate matter (wind, sea, fire etc.) and some among the animals and plants.
A common feature of all such forms of inanimate and animate objects was the sense of awe or fear that they evoked.
The description of living organisms including human beings began much later in human history.
Societies which indulged in anthropocentric view of biology could register limited progress in biological knowledge. Systematic and monumental description of life forms brought in, out of necessity, detailed systems of identification, nomenclature and classification.
The biggest spin off of such studies was the recognition of the sharing of similarities among living organisms both horizontally and vertically.
That all present day living organisms are related to each other and also to all organisms that ever lived on this earth, was a revelation which humbled man and led to cultural movements for conservation of biodiversity. In the following chapters of this unit, you will get a description, including classification, of animals and plants from a taxonomist’s perspective.
Ernst MayrBorn on 5 July 1904, in Kempten, Germany, ERNST MAYR, the Harvard University evolutionary biologist who has been called
‘The Darwin of the 20th century’,
was one of the 100 greatest scientists of all time.
Mayr joined Harvard’s Faculty of Arts and Sciences in 1953 and retired in 1975,
assuming the title Alexander Agassiz Professor of Zoology Emeritus.

Throughout his nearly 80-year career, his research spanned
ornithology, taxonomy,
zoogeography,
evolution,
systematics,
and the history
and philosophy of biology,
almost single-handedly made the origin of species diversity the central question of evolutionary biology that it is today.
He also pioneered the currently accepted definition of a biological species.
Mayr was awarded the three prizes widely regarded as the triple crown of biology the Balzan Prize in 1983,
the International Prize for Biology in 1994,
and the Crafoord Prize in 1999.
Mayr died at the age of 100 in the year 2004.

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Extract. 8.1. How wonderful is the living world ! The wide range of living types is amazing.
The extraordinary habitats in which we find living organisms, be it cold mountains, deciduous forests, oceans,
fresh water lakes, deserts or hot springs, leave us speechless. The beauty of a galloping horse, of the migrating birds,
the valley of flowers or the attacking shark evokes awe and a deep sense of wonder.
The ecological conflict and cooperation among members of a population and among populations of a community or even the molecular traffic inside a cell make us deeply reflect on –

Extract. 9-12. what indeed is life?
This question has two implicit questions within it.
The first is a technical one and seeks answer to what living is as opposed to the non-living,
and the second is a philosophical one, and seeks answer to what the purpose of life is.
As scientists, we shall not attempt answering the second question.
We will try to reflect on –What is ‘living’?-
When we try to define ‘living’, we conventionally look for distinctive characteristics exhibited by living organisms.
Growth, reproduction, ability to sense environment and mount a suitable response come to our mind immediately as unique features of living organisms.
One can add a few more features like metabolism, ability to self-replicate, self-organise, interact and emergence to this list. Let us try to understand each of these
. All living organisms grow. Increase in mass and increase in number of individuals are twin characteristics of growth.
A multicellular organism grows by cell division. In plants, this growth by cell division occurs continuously throughout their life span. In animals, this growth is seen only up to a certain age.
However, cell division occurs in certain tissues to replace lost cells. Unicellular organisms also grow by cell division. One can easily observe this in vitro cultures by simply counting the number of cells under the microscope. In majority of higher animals and plants, growth and reproduction are mutually exclusive events.

Extract. 13.20. One must remember that increase in body mass is considered as growth. Non-living objects also grow if we take increase in body mass as a criterion for growth. Mountains, boulders and sand mounds do grow. However, this kind of growth exhibited by non-living objects is by accumulation of material on the surface. In living organisms, growth is from inside. Growth, therefore, cannot be taken as a defining property of living organisms. Conditions under which it can be observed in all living organisms have to be explained and then we understand that it is a characteristic of living systems. A dead organism does not grow.
Reproduction, likewise, is a characteristic of living organisms. In multicellular organisms, reproduction refers to the production of progeny possessing features more or less similar to those of parents. Invariably and implicitly we refer to sexual reproduction. Organisms reproduce by asexual means also. Fungi multiply and spread easily due to the millions of asexual spores they produce. In lower organisms like yeast and hydra, we observe budding. In Planaria (flat worms), we observe true regeneration, i.e., a fragmented organism regenerates the lost part of its body and becomes, a new organism. The fungi, the filamentous algae, the protonema of mosses, all easily multiply by fragmentation. When it comes to unicellular organisms like bacteria, unicellular algae or Amoeba, reproduction is synonymous with growth, i.e., increase in number of cells.
Extract(21-30). We have already defined growth as equivalent to increase in cell number or mass. Hence, we notice that in single-celled organisms, we are not very clear about the usage of these two terms – growth and reproduction. Further, there are many organisms which do not reproduce (mules, sterile worker bees, infertile human couples, etc). Hence, reproduction also cannot be an all-inclusive defining characteristic of living organisms. Of course, no non-living object is capable of reproducing or replicating by itself. Another characteristic of life is metabolism. All living organisms are made of chemicals. These chemicals, small and big, belonging to various classes, sizes, functions, etc., are constantly being made and changed into some other biomolecules. These conversions are chemical reactions or metabolic reactions. There are thousands of metabolic reactions occurring simultaneously inside all living organisms, be they unicellular or multicellular. All plants, animals, fungi and microbes exhibit metabolism.
The sum total of all the chemical reactions occurring in our body is metabolism. No non-living object exhibits metabolism. Metabolic reactions can be demonstrated outside the body in cell-free systems. An isolated metabolic reaction(s) outside the body of an organism, performed in a test tube is neither living nor non-living. Hence, while metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things but surely living reactions Hence, cellular organisation of the body is the defining feature of life forms. Perhaps, the most obvious and technically complicated feature of all living organisms is this ability to sense their surroundings or environment and respond to these environmental stimuli which could be physical, chemical or biological. We sense our environment through our sense organs. Plants respond to external factors like light, water, temperature, other organisms, pollutants, etc. All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues.
Photoperiod affects reproduction in seasonal breeders, both plants and animals. All organisms handle chemicals entering their bodies. All organisms therefore, are ‘aware’ of their surroundings. Human being is the only organism who is aware of himself i.e., has self-consciousness. Consciousness therefore, becomes the defining property of living organisms.
When it comes to human beings, it is all the more difficult to define the living state. We observe patients lying in coma in hospitals virtually supported by machines which replace heart and lungs. The patient is otherwise brain-dead. The patient has no self-consciousness. Are such patients who never come back to normal life, living or non-living? In higher classes, you will come to know that all living phenomena are due to underlying interactions. Properties of tissues are not present in the constituent cells but arise as a result of interactions among the constituent cells. Similarly, properties of cellular organelles are not present in the molecular constituents of the organelle but arise as a result of interactions among the molecular components comprising the organelle. These interactions result in emergent properties at a higher level of organisation. This phenomenon is true in the hierarchy of organizational complexity at all levels Therefore, we can say that living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli. Biology is the story of life on earth.
Biology is the story of evolution of living organisms on earth. All living organisms – present, past and future, are linked to one another by the sharing of the common genetic material, but to varying degrees.
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Extract(31-42) 1.2 DIVERSITY IN THE LIVING WORLD If you look around you will see a large variety of living organisms, be it potted plants, insects, birds, your pets or other animals and plants. There are also several organisms that you cannot see with your naked eye but they are all around you. If you were to increase the area that you make observations in, the range and variety of organisms that you see would increase. Obviously, if you were to visit a dense forest, you would probably see a much greater number and kinds of living organisms in it. Each different kind of plant, animal or organism that you see, represents a species. The number of species that are known and described range between 1.7-1.8 million. This refers to biodiversity or the number and types of organisms present on earth. We should remember here that as we explore new areas, and even old ones, new organisms are continuously being identified.
As stated earlier, there are millions of plants and animals in the world; we know the plants and animals in our own area by their local names. These local names would vary from place to place, even within a country. Probably you would recognise the confusion that would be created if we did not find ways and means to talk to each other, to refer to organisms we are talking about. Hence, there is a need to standardise 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. Obviously, nomenclature or naming is only possible when the organism is described correctly and we know to what organism the name is attached to. This is identification. In order to facilitate the study, number of scientists have established procedures to assign a scientific name to each known organism. This is acceptable to biologists all over the world.
For plants, scientific names are based on agreed principles and criteria, which are provided in International Code for Botanical Nomenclature (ICBN). You may ask, how are animals named?
Animal taxonomists have evolved International Code of Zoological Nomenclature (ICZN). The scientific names ensure that each organism has only one name. Description of any organism should enable the people (in any part of the world) to arrive at the same name. They also ensure that such a name has not been used for any other known organism.
Biologists follow universally accepted principles to provide scientific names to known organisms. Each name has two components – the Generic name and the specific epithet.
This system of providing a name with two components is called Binomial nomenclature This naming system given by Carolus Linnaeus is being practised by biologists all over the world. This naming system using a two word format was found convenient. Let us take the example of mango to understand the way of providing scientific names better.
The scientific name of mango is written as Mangifera indica.
Let us see how it is a binomial name. In this name Mangifera represents the genus while indica, is a particular species, or a specific epithet. Other universal rules of nomenclature are as follows to which species mango belongs to.
1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.
3. Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin
4. The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter. It can be illustrated with the example of Mangifera indica.
Name of the author appears after the specific epithet, i.e., at the end of the biological name and is written in an abbreviated form, e.g., Mangifera indica Linn. It indicates that this species was first described by Linnaeus. Since it is nearly impossible to study all the living organisms, it is necessary to devise some means to make this possible. This process is classification. Classification is the process by which anything is grouped into convenient categories based on some easily observable characters.
For example, we easily recognise groups such as plants or animals or dogs, cats or insects. The moment we use any of these terms, we associate certain characters with the organism in that group. What image do you see when you think of a dog ? Obviously, each one of us will see ‘dogs’ and not ‘cats’. Now, if we were to think of ‘Alsatians’ we know what we are talking about. Similarly, suppose we were to say ‘mammals’, you would, of course, think of animals with external ears and body hair. Likewise, in plants, if we try to talk of ‘Wheat’, the picture in each of our minds will be of wheat plants, not of rice or any other plant. Hence, all these - ‘Dogs’, ‘Cats’, ‘Mammals’, ‘Wheat’, ‘Rice’, ‘Plants’, ‘Animals’, etc., are convenient categories we use to study organisms.
The scientific term for these categories is taxa. Here you must recognise that taxa can indicate categories at very different levels. ‘Plants’ – also form a taxa. ‘Wheat’ is also a taxa. Similarly, ‘animals’, ‘mammals’, ‘dogs’ are all taxa – but you know that a dog is a mammal and mammals are animals. Therefore, ‘animals’, ‘mammals’ and ‘dogs’ represent taxa at different levels. Hence, based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy. External and internal structure, along with the structure of cell, development process and ecological information of organisms are essential and form the basis of modern taxonomic studiesHence, characterisation, identification, classification and nomenclature are the processes that are basic to taxonomy.
Taxonomy is not something new. Human beings have always been interested in knowing more and more about the various kinds of organisms, particularly with reference to their own use. In early days, human beings needed to find sources for their basic needs of food, clothing and shelter. Hence, the earliest classifications were based on the ‘uses’ of various organisms.
Human beings were, since long, not only interested in knowing more about different kinds of organisms and their diversities, but also the relationships among them. This branch of study was referred to as systematics. The word systematics is derived from the Latin word ‘systema’ which means systematic arrangement of organisms. Linnaeus used Systema Naturae as the title of his publication. The scope of systematics was later enlarged to include identification, nomenclature and classification. Systematics takes into account evolutionary relationships between organisms.
Taxonomic Categories
Classification is not a single step process but involves hierarchy of steps in which each step represents a rank or category.
Since the category is a part of overall taxonomic arrangement, it is called the taxonomic category and all categories together constitute the taxonomic hierarchy.
Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as taxon (pl.: taxa). Taxonomic categories and hierarchy can be illustrated by an example. Insects represent a group of organisms sharing common features like three pairs of jointed legs.
It means insects are recognisable concrete objects which can be classified, and thus were given a rank or category. Can you name other such groups of organisms?
Remember, groups represent category. Category further denotes rank. Each rank or taxon, in fact, represents a unit of classification. These taxonomic groups/ categories are distinct biological entities and not merely morphological aggregates. Taxonomical studies of all known organisms have led to the development of common categories such as kingdom, phylum or division (for plants), class, order, family, genus and species.
All organisms, including those in the plant and animal kingdoms have species as the lowest category. Now the question you may ask is, how to place an organism in various categories?
The basic requirement is the knowledge of characters of an individual or group of organisms.
This helps in identifying similarities and dissimilarities among the individuals of the same kind of organisms as well as of other kinds of organisms. Species Taxonomic studies consider a group of individual organisms with fundamental similarities as a species.
One should be able to distinguish one species from the other closely related species based on the distinct morphological differences.
Let us consider Mangifera indica, Solanum tuberosum (potato) and Panthera leo (lion).
All the three names, indica, tuberosum and leo, represent the specific epithets, while the first words Mangifera, Solanum and Panthera are genera and represents another higher level of taxon or category.
Each genus may have one or more than one specific epithets representing different organisms, but having morphological similarities.
For example, Panthera has another specific epithet called tigris and Solanum includes species like nigrum and melongena. Human beings belong to the species sapiens which is grouped in genus Homo. The scientific name thus, for human being, is written as Homo sapiens.
Genus Genus comprises a group of related species which has more characters in common in comparison to species of other genera.
We can say that genera are aggregates of closely related species.
For example, potato, tomato and brinjal are three different species but all belong to the genus Solanum.
Lion (Panthera leo), leopard (P. pardus)
and tiger (P. tigris) with several common features, are all species of the genus Panthera. This genus differs from another genus Felis which includes cats.
Family
The next category, Family, has a group of related genera with still less number of similarities as compared to genus and species. Families are characterised on the basis of both vegetative and reproductive features of plant species. Among plants for example, three different genera Solanum, Petunia and Datura are placed in the family Solanaceae. Among animals for example, genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) in the family Felidae. Similarly, if you observe the features of a cat and a dog, you will find some similarities and some differences as well. They are separated into two different families – Felidae and Cancidae, respectively.
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1.3.4 Order You have seen earlier that categories like species, genus and families are based on a number of similar characters. Generally, order and other higher taxonomic categories are identified based on the aggregates of characters. Order being a higher category, is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family. Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales mainly based on the floral characters. The animal order, Carnivora, includes families like Felidae and Cancidae.
1.3.5 Class
This category includes related orders. For example, order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog. Class Mammalia has other orders also.
1.3.6 Phylum
Classes comprising animals like fishes, amphibians, reptiles, birds along with mammals constitute the next higher category called Phylum. All these, based on the common features like presence of notochord and dorsal hollow neural system, are included in phylum Chordata. In case of plants, classes with a few similar characters are assigned to a higher category called Division.
1.3.7 Kingdom
All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia in the classification system of animals. The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions. Henceforth, we will refer to these two groups as animal and plant kingdoms.
The taxonomic categories from species to kingdom have been shown in ascending order starting with species in Figure 1.1. These are broad categories. However, taxonomists have also developed sub-categories in this hierarchy to facilitate more sound and scientific placement of various taxa. Look at the hierarchy in Figure 1.1. Can you recall the basis of arrangement? Say, for example, as we go higher from species to kingdom, the number of common characteristics goes on decreasing. Lower the taxa, more are the characteristics that the members within the taxon share. Higher the category, greater is the difficulty of determining the relationship to other taxa at the same level. Hence, the problem of classification becomes more complex. Table 1.1 indicates the taxonomic categories to which some common organisms like housefly, man, mango and wheat belong.
1.4 TAXONOMICAL AIDS
Taxonomic studies of various species of plants, animals and other organisms are useful in agriculture, forestry, industry and in general in knowing our bio-resources and their diversity. These studies would require correct classification and identification of organisms. Identification of organisms requires intensive laboratory and field studies. The collection of actual specimens of plant and animal species is essential and is the prime source of taxonomic studies. These are also fundamental to studies and essential for training in systematics. It is used for classification of an organism, and the information gathered is also stored along with the specimens. In some cases the specimen is preserved for future studies. Biologists have established certain procedures and techniques to store and preserve the information as well as the specimens. Some of these are explained to help you understand the usage of these aids.
1.4.1 Herbarium
Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets. Further, these sheets are arranged according to a universally accepted system of classification. These specimens, along with their descriptions on herbarium sheets, become a store house or repository for future use (Figure 1.2). The herbarium sheets also carry a label providing information about date and place of collection, English, local and botanical names, family, collector’s name, etc. Herbaria also serve as quick referral systems in taxonomical studies.
1.4.2 Botanical Gardens
These specialised gardens have collections of living plants for reference. Plant species in these gardens are grown for identification purposes and each plant is labelled indicating its botanical/scientific name and its family. The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and at National Botanical Research Institute, Lucknow (India).
1.4.3 Museum
Biological museums are generally set up in educational institutes such as schools and colleges. Museums have collections of preserved plant and animal specimens for study and reference. Specimens are preserved in the containers or jars in preservative solutions. Plant and animal specimens may also be preserved as dry specimens. Insects are preserved in insect boxes after collecting, killing and pinning. Larger animals like birds and mammals are usually stuffed and preserved. Museums often have collections of skeletons of animals too. 1.4.4 Zoological Parks These are the places where wild animals are kept in protected environments under human care and which enable us to learn about their food habits and behaviour. All animals in a zoo are provided, as far as possible, the conditions similar to their natural habitats. Children love visiting these parks, commonly called Zoos (Figure 1.3).
1.4.5 Key Key is another taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. It represents the choice made between two opposite options. This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes.
Keys are generally analytical in nature. Flora, manuals, monographs and catalogues are some other means of recording descriptions. They also help in correct identification. Flora contains the actual account of habitat and distribution of plants of a given area. These provide the index to the plant species found in a particular area. Manuals are useful in providing information for identification of names of species found in an area. Monographs contain information on any one taxon.
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Comprehension 1. Define biology.
2. Name any two in animate matter.
3. What do you mean by anthropocentric?
Hint- Anthropocentrism is the belief that human beings are the most important entity in the universe.
4. Who was called the Darwin of 20th century?
5. Name the fields in which the search of earnest Mayr spanned.
6. Who gave the present definition of biological species?
7. Which prizes in Biology comprise triple crown?
8. When Mayr joined Harvard’s Faculty of Arts and Sciences?
9. What indeed is life? Explain two implicit questions in it?
10. Give any two characteristics of Living organisms?
11. Which are two characteristics of growth?
12. What you will call the increased of body mass?
13. How can non living objects grow in size? Can we call it growth in biological terms.
14. What is reproduction?
15. Name two organisms in which you observe budding.
16. What is true regeneration? Name the organism in which it takes place.
17. Name three types of organisms in which fermentation take place.
18. In which organism reproduction is synonyms with growth?
19. Draw well labeled diagram of Hydra.
20. Draw well labeled diagram Planaria.
21. Name three organisms and their types which do not reproduce?
22. what is metabolism.
23. What do you mean by in vitro?
24. Name any three external factors to which plants respond.
25. What do you understand by the term prokaryote?
26. What do you mean by eukaryotes?
27. What is photoperiodism?
28. Which is the only organism which is aware of himself?
29. What type of systems living organisms are?
30. What type of story Biology is?
31. What is the range of known species in the world?
32. Can we use local names of plants and animals for our study, if not why?
33. What is nomenclature?
34. What do you mean by identification?
35. What is full form of ICBN?
36. What is full form of ICZN?
37. What we ensure by using a scientific name?
38. How description is useful?
39. Which are two components of a name?
40. What do you call the system in which two words are used for naming?
41. Who gave the present system of naming of organisms?
42. What is scientific name of mango?
43. to which genus mango belongs to?

44. in which language biological names are generally written?
45. what is represented by the first word in a biological name also mention what is represented by the second world?
46. What should we do when we write word in manuscript for handwritten?
47. How the words are printed to write scientific name.
48. Which word starts with a capital letter in the scientific name? 49. Where the name of the author is written in the scientific name? 50. In which form the name of the author is written in the scientific name?
51. What do you mean by classification in biological naming?
52. What is the scientific term for various categories?
53. What forms the basis of modern taxonomic studies?
54. Which processes are basic to taxonomy?
55. Which were the basic needs in the early year?
56. What is systematics?
57. Who wrote systema naturae?
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NCERT QAs

1. Why are living organisms classified?

1. A large variety of plants, animals, and microbes are found on earth. All these living organisms differ in size, shape, colour, habitat, and many other characteristics. As there are millions of living organisms on earth, studying each of them is impossible. Therefore, scientists have devised mechanisms to classify all living organisms. These methods of classification are based on rules and principles that allow identification, nomenclature, and finally classification of an organism.
For example, based on certain principles, once an organism is identified as an insect, it will be given a scientific name and then grouped with other similar organisms. Thus, various groups or taxon include organisms based on their similarity and differences.
Therefore, the biological classification helps in revealing the relationship between various organisms. It also helps in making study of organisms easy and organized.

2. Why are the classification systems changing every now and then?

2. Millions of plants, animals, and microorganisms are found on earth. Many of these have been identified by the scientists while many new species are still being discovered around the world. Therefore, to classify these newly discovered species, new systems of classification have to be devised every now and then. This creates the requirement to change the existing systems of classification.

3. What different criteria would you choose to classify people that you meet often?

3. To classify a class of forty students, let us start the classification on the basis of sexes of the students. This classification will result in the formation of two major groups- boys and girls. Each of these two groups can be further classified on the basis of the names of the students falling in these groups.
Since it is possible that more than one student can have a particular name, these names can be further divided based on the surnames. Since there is still some chance that more than one student can have the same surname, the final level of classification will be based on the roll numbers of each student.

4. What do we learn from identification of individuals and populations?

4. The knowledge of characteristics of an individual or its entire population helps in the identification of similarities and dissimilarities among the individuals of same kind or between different types of organisms. It helps the scientists to classify organisms in various categories.

5. Given below is the scientific name of Mango. Identify the correctly written name. Mangifera Indica Mangifera indica

5. In binomial system of nomenclature, the generic name of a species always starts with a capital letter whereas the specific name starts with a small letter. Therefore, the correct scientific name of Mango is Mangifera indica.

6. Define a taxon. Give some examples of taxa at different hierarchical levels.

6. Each unit or category of classification is termed as a taxon. It represents a rank. For example, the basic level of classification is species, followed by genus, family, order, class, phylum or division, in ascending order. The highest level of classification is known as kingdom.

7. Can you identify the correct sequence of taxonomical categories? (a) Species ⟶ Order ⟶ Phylum ⟶ Kingdom (b) Genus ⟶ Species ⟶ Order ⟶ Kingdom (c) Species ⟶ Genus ⟶ Order ⟶ Phylum

7. The correct hierarchical arrangement of taxonomic categories in ascending order is Species ⟶ Genus ⟶ Family ⟶ Order ⟶ Class ⟶ Phylum ⟶ Kingdom
Therefore, both (a) and (c) represent correct sequences of taxonomic categories. In sequence (b), species should be followed by genus. Therefore, it does not represent the correct sequence.

8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand and bacteria on the other hand.

8. In biological terms, species is the basic taxonomical rank. It can be defined as a group of similar organisms that are capable of interbreeding under natural conditions to produce fertile offspring. Therefore, a group of similar individuals that are respectively isolated form a species. Species can also be defined as group of individuals that share the same gene pool.

9. Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus

9. (i) Phylum Phylum is the primary division of kingdom. It includes one or more related classes of animals. In plants, instead of phylum, the term -division is used.
(ii) Class. Class is a taxonomic group consisting of one or more related orders. For example, the class, Mammalia, includes many orders.
(iii) Family. Family is a taxonomic group containing one or more related genera. In plants, families are categorized on the basis of vegetative and reproductive features.
(iv) Order. Order is a taxonomic group containing one or more families. For example, the order, carnivore, includes many families.
(v) Genus. Genus is a taxonomic group including closely related species. For example, the genus, Solanum, includes many species such as nigrum, melongena, tuberosum, etc.

10. How is a key helpful in the identification and classification of an organism?

10. Key is another taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. It represents the choice made between two opposite options.
This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Keys are generally analytical in nature.

Flora, manuals, monographs and catalogues are some other means of recording descriptions. They also help in correct identification.
Flora contains the actual account of habitat and distribution of plants of a given area. These provide the index to the plant species found in a particular area.

Manuals are useful in providing information for identification of names of species found in an area. Monographs contain information on any one taxon.

11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.

11. The arrangement of various taxa in a hierarchical order is called taxonomic hierarchy. In this hierarchy, species is present at the lowest level whereas kingdom is present at the highest level.
Classification of a plant
As an example, let us classify Solanum melongena (Brinjal).
Kingdom - Plantae
Division - Angiospermae
Class -Dicotyledonae
Order - Solanales
Family - Solanaceae
Genus -Solanum
Species - melongena
Classification of an animal As an example, let us classify Columba livia (Blue rock Dove). Kingdom - Animalia
Phylum -Chordata
Class - Aves
Order - Columbiformes
Family - Columbidae
Genus -Columba
Species - livia
Notes
Genus It is an assembly of related species which evolved from a common ancestor and have certain common characters called correlated characters.
Potato (Solanum tuberosum) and Brinjal (Solanum melongena) are two species which belong to same genus (of Solanum) and have many correlated characters. Similarly Lion (Panthera leo) and Tiger (Panthera tigris) have several common features and are included in the same genus (of Panthera). A genus having two or more species is called polytypic genus. A genus with a single species is known as monotypic genus, e.g.; Homo (Homo sapiens).
Family It is a taxonomic category which includes one or more related genera. All the genera of a family have some common or correlated features which are different from those of genera of another family. Solanum, Petunia and Atropa belong to family solanaceae. Panthera (genus of big cats) and Felis (genus of cats) belong to family F.elidae. The correlated traits of Panthera and Felis will be quite different from those of various genera of family Canidae (family of dogs and related genera). In plants the family ends in the suffix. - aceae and subfamily in -oideae while in animals the suffixes are -idae for family, -inae for sub-family, -ini for tribe (between subfamily and genus) and -oidea for superfamily.
Order Order is a taxonomic category which includes one or more related families with some common features, e.g., Solanaceae and Convolvulaceae in order Polymoniales,
Felidae and Canidae in order Carnivora.
It ends in suffix -ales in plants. Different suffixes are used in case of animals.
Cohort. Used differently by different authors as (i) group of releated species (ii) group between order and class and (iii) group above the rank of super-order.
Class (Linnaeus, 1735). It is a taxonomic category made of one or more related orders, e.g., Class Mammalia with orders like Carnivora, Primata, Cetacea, Insectivora, Chiroptera, etc.
All the orders of a class possess some similar correlated characters.
Class ends in suffixes -phyceae, -opsida and -ae in plants. The suffix is not fixed in case of animals.
Division (Eichler) or Phylum (Cuvier, 1829). It is a taxonomic category that includes one or more related classes.
All the classes of a phylum possess some common correlated traits, e.g., notochord, dorsal hollow nerve chord and gill slits in classes Pisces, Amphibia, Reptilia, Aves and Mammalia of phylum chordata. Phylum does not have a fixed suffix.
Division is given the suffix -phyta and the subdivision -phytina. Kingdom. Kingdom is the highest taxonomic category, e.g., Kingdom Planta, Kingdom Animalia.
Systems of Biological Classifications There are three systems of classification - artificial, natural and phylogenetic.
Artificial Systems of Classification
They are systems of classification in which habit, habitat and a few morphological characters are used for grouping of organisms. All early systems of classification (e.g., given by Aristotle, Theophrastus, Pliny, Bauhin, John Ray, Linnaeus, etc.) were artificial.
Aristotle (384-322 B.C.) grouped animals into enaima (with red blood), anaima (without red blood), ovipera (egg laying) and vivipera (giving birth to young ones).
He also classified animals on the basis of habitat into water, land and air.
Theopharastus (370- 284 B.C.) grouped plants on the basis of their habits into trees, shrubs and herbs.
Pliny the Elder (23-79 AD.) divided animals into flight and nonflight animals.
Linnaeus (1735-37) divided angiosperms on the basis of numerical strength of essential organs, e.g., cryptogamia, monandria, diandria, polyandria, monoecia, etc.
Artificial systems are simpler and easier to practise in the field but they have several drawbacks
(i) The grouping is based on external features which may appear due to parallel evolution, retrogressive evolution or progressive evolution.
(ii) Grouping on the basis of habit would put Pinus and Eucalyptus in one group. Similalry ferns and Phlox would from another group.
(iii) Use of habitat as criterion for classification will assemble whale and fish or butterfly and bird in one group.
(iv) Organisms of different affinities may come in the same group, e.g., Vitis (a dicot) and Asparagus (a monocot) in classification of Linnaeus.
(v) Closely related organisms get separated into different groups, e.g., Bat, Whale and Panther.
(vi) The traits used for artificial system are liable to change.
(vii) Natural relationships are not brought out.
Natural Systems of Classification
They are systems of classification where organisms are arranged according to their natural affinities through the use of all important permanent characteristics, especially structural, cytological (chromosomal) reproductive and biochemical. The characters are useful in bringing out homology.
The first natural system of plant classification was proposed by Schimper (1879) followed by Eichler (1883).
The most important and last of natural systems for classification of seed plants was developed by Bentham (1800 -1884) and Hooker (1817 -1911) in the treatise called Genera Plantarum (1862-1883).
The first natural system of animal classification was developed by Linnaeus in his book "Systema Naturae" (tenth edition 1758). Improvements were subsequently made by Haeckel (1864) and Lankester (1874).
Phylogenetic Systems of Classification They are those systems of classification which bring out evolutionary relationships of organisms.
Phylogenetic systems of classification came into existence after the acceptance of doctrine of evolution and natural selection propounded by Charles Darwin in his book "On the origin of Species by means of Natural Selection or The Preservation of Races in the Struggle for Life" (1859).
All modern day species and other taxa are product of evolution being lineages or branches of the past taxa.
Therefore, phylogenetic systems are also called cladistics. Graphic representation of evolutionary relationships is called family tree or cladogram.
A family tree based on phenetic or numerical taxonomy is called dendrogram. Takhtajan (1967) has likened taxonomy without phylogeny to be bones without flesh.
Phylogenetic system of classification was first proposed by Engler (1844-1930) and Prantl (1849-1893) in their monograph Die Naturlichen Pflanzen Familien (1887-1899).
They arranged families and orders of flowering plants in ascending series from simple (achlamydeous. or monochlamydeous unisexual flowers with anemophily) to complex (dichlamydeous bisexual flowers with entomophily).
Monocots were considered primitive to dicots.
They considered asteraceae (amongst dicots) and Orchidaceae (amongst monocots) to be most advanced.
Better phylogenetic systems were developed by Hutchinson (1920, 1934, 1948, 1973), Takhtajan (1967, 1980) and Cronquist (1981).
Attempts have also been made to develop phylogenetic systems of classification for animals by Dobzhansky and Mayr.
Two Kingdom System - Animal or Plant
Biologists since the time of Aristotle, have divided the living organisms into plants and animals.
Linnaeus placed them into two kingdoms of plantae (all plants) and animalia (all animals).
Kingdom Plantae.
The plant kingdom has the following characteristic features:
a. They are non-motile.
b. They make their own food and hence are called autotrophs.
c. They reproduce asexually by vegetative propagation or sexually.
d. These are multicellular eukaryotes. Cells have a rigid cell wall, a central vacuole, plastids and inorganic crystals. Plants contain photosynthetic pigments called chlorophyll present in the plastids. Centrosome is generally absent.
e. They have different organelles for anchorage, reproduction, support and photosynthesis. Asexual reproduction is common. It occurs through vegetative propagation and spores.
f. Sexual reproduction requires the help of an external agency like water, wind, insects, etc.
Kingdom Plantae includes bacteria, fungi, algae, liverworts, mosses, hornworts, ferns and other pteridophytes, gymnosperms and angiosperms. Classification is based on the following criteria:
i. Plant body: Presence or absence of a well-differentiated plant body. E.g. Root, Stem and Leaves.
ii. Vascular system: Presence or absence of a vascular system for the transportation of water and other substances. E.g. Phloem and Xylem.
iii. Seed formation: Presence or absence of flowers and seeds and if the seeds are naked or enclosed in a fruit.
The plant kingdom is also classified into two groups:
Cryptogams
- Non-flowering and non-seed bearing plants. e.g. Thallophyta, Bryophyta, Pteridophyta
Phanerogams
- Flowering and seed-bearing plants. e.g. Gymnosperms, Angiosperms
Kingdom Animalia.
The kingdom includes animals which are mobile organisms with holozoic or ingestive type of nutrition, regular form, internal organs, limited but diffused growth and reserve food of glycogen. Sensory and excretory organs are present. Animals are quick to respond to stimuli. Cells are 'without cell walls. Plastids and inorganic salts are absent. A few small vacuoles occur instead of a central vacuole. Centrosome is present. Higher animals do not reproduce asexually. Sexual reproduction does not require ,an external agency. Kingdom Animalia includes protozoans, sponges, jellyfishes, worms, insects, crabs, centipedes, millipedes, spiders, snails, starfishes, sharks, frogs, lizards, birds and mammals. → Explain the characteristic of Thallophytes.
Members of this class lack a well-differentiated body structure, or in other words, the body is not clearly divided into stem, leaves and roots.
Significant features of Gymnosperms.
Gymnosperms include plants that possess a vascular system and a well-differentiated body structure. Furthermore, they bear seeds like the angiosperms, but they are not encased within a fruit. Hence, the term-Gymnosperm , which is derived from Greek word, gymno = naked and Sperma = seed.
Characteristics of Angiosperms.
Seed-bearing plants
Seeds are enclosed within fruits
Presence of well-differentiated plant body
Produce flowers during their lifespan
Presence of two subtypes - monocots and dicots ↔
Shortcomings of Two-Kingdom System
The two-kingdom system of classification given by Linnaeus in 1758 worked well for a long time. However, with the expansion of our knowledge about the different types of organisms a number of shortcomings were found in the two kingdom system of classification.
1. Tunicates is a group of chordate animals which have cellulose, branching and anchorage just like plants.
2. Sponges and corals are nonmotile. They are fixed like plants. The form is often irregular similarly.
3. Viruses are often included amongst plants of two kingdom classification. They are neither plants nor animals and lie at the border line of living and nonliving.
4. Bacteria and cyanobacteria are prokaryotic. They are included under plants which are otherwise eukaryotes.
5. Unicellular organisms can be colourless, green, red or brown. It is very difficult to distinguish them as plants and animals.
6. Both the kingdoms contain unicellular and multicellular forms though they have different organisation.
7. Certain unicellular organisms are being studied by both botanists and zoologists, e.g., Euglena. They are called dual organisms because of the presence of characters of both the groups, e.g., chloroplasts, periplast, food reserve, flagella, gullet, contractibility, etc. Euglena has mixohophic nutrition (both holophytic/autotrophic and saprotrophic).
8. Kingdom plantae contains fungi which are nonphotosynthetic, possess chitin wall and glycogen as reserve food. They are often grouped along with photosynthetic algae as thallophytes.
9. Early organisms were neither plant-like nor animal-like. Some of them later gradually evolved along plant and animal lines. Definite plant or animal status was attained quite later in the evolutionary history. Therefore, the traditional two kingdom system of classification seems inadequate and inappropriate.
Three Kingdom System
Earnst Haeckel (1866), a German Biologist, suggested that a third kingdom Protista be established to include all organisms lacking tissue differentiation such as Protozoa, unicellular/acellular algae, fungi and bacteria. Drawbacks of two-kingdom system, persist in this system also.
(i) Acellular and multicellular organisms are kept together in Protista.
(ii) Bacteria and fungi have been grouped with unrelated organisms. Four Kingdom System
The system was developed by Copeland (1956). It has four kingdoms of Plantae, Animalia, Protista and Monera (= Mychota).
Monera includes prokaryotes (bacteria and blue-green algae). Protista has single-celled eukaryotic organisms. The main drawback of this system is that fungi are not properly placed. Five Kingdom System of Whittaker
Robert H. Whittaker (1969), an American taxonomist, has proposed a five kingdom classification on the basis of (i) Prokaryotic and eukaryotic nature.
(ii) Unicellularity and multicellularity.
(iii) Mode of nutrition like holophytic, absorptive and ingestive,
(iv) Source of nutrition - autotrophic and heterotrophic,
(v) Ecological life style like producers, consumers and decomposers,
(vi) Phylogenetic relationships,
The five kingdoms of classification are:
Monera
Protista
Fungi
Plantae/Metaphyta (Plants)
Animalia/Metazoa (Animals).
Kingdom Monera . It includes all prokaryotes – mycoplasma, bacteria, archaeobacteria, eubacteria, actinomycetes and cyanobacteria.
They are basically unicellular but can be mycelial, colonial and filamentous. Cells are small (0.2-10µm3 or compared to 10-6 - 10-3 µ m3 in viruses and 1000 -10000 µm3 in eukaryotes) with peptidoglycan in cell wall, one envelope organisation, single DNA double strand coiled to form nucleoid without association with histones, ribosomes 70S, thylakoids present in photoautotrophs but other membrane bound organelles are absent.
A spindle is not formed. Flagella if present are single stranded.
Nutrition is varied - saprobic, parasitic, chemoautotrophic, photo autotrophic and saprobic.
Habitat varied but also under stressful conditions of salt pans, sulphur springs, hot springs, snow, petroleum pans, etc. Sexual reproduction is absent. Some monerans have the ability to fix nitrogen.
Kingdom Protista.
The kingdom contains unicellular and colonial eukaryotes like flagellates, diatoms, dinoflagellates, slime moulds, water moulds, sarcodines, ciliates and sporozoans (formerly in protozoa).
Nutritionally they can be photosynthetic (commonly as phytoplankton), holozoic(commonly as zooplankton), chemoautotrophic, hemoheterotrophic, saprobic and parasitic.
Cell wall is present in photosynthetic forms and absent in others. Certain forms are mixotrophic- photosynthetic in light and nongreen saprobic or holozoic in dark, e.g., Euglena.
Some of the saprobes live as symbionts in the gut of termites and wood eating cockroaches for digestion of cellulose. Slime moulds are naked with ingestive (holozoic) nutrition in vegetative phase and walled in reproductive phase. Cell organisation is of two envelope type. A distinct nucleus is present. Ribosome are 80 S. Membrane bound organelles occur.
Flagella if present, are single stranded. Reproduction is both asexual and sexual but embryo stage is absent.
Kingdom Fungi. It is kingdom of achlorophyllous, spore producing, multicellular or multinucleate eukaryotic organisms having absorptive type of nutrition (either saprobic or parasitic).
Unicellular yeasts are also included under fungi. Some form symbiotic association, e.g., lichens (with algae),mycorrhiza (with roots of higher plants).
Body is mycelium being made of a number of hyphae or filaments. Tissue system is absent. Nuclei are small. Spindle is intranuclear. Wall is present. It contains chitin.
Cell organisation is double envelope type. Food reserve is glycogen. Reproduction is both asexual and sexual but sex organs undergo retrogressive evolution. Embryo stage is absent. Kingdom contains all fungi, except slime moulds and related forms, e.g., bread moulds, yeasts, mushrooms, rusts, etc.
Kingdom Plantae or Metaphyta .
They are multicellular eukaryotic, photosynthetic organisms and their close relatives (some unicellular algae, nonphotosynthetic parasites or saprobes), e.g., green algae, brown algae, red algae, bryophytes, pteridophytes and spermatophytes. Plants are mostly fixed.
Motility occurs in some algae and reproductive cells of lower plants. Growth is often indefinite by means of growing points.
Tissue systems have developed in higher forms. Cell wall is present. It contains cellulose. Cells contain central vacuoles, plastids and starch as food reserve. Reproduction is both asexual and sexual. Embryo stage is present except in algae.
Kingdom Animalia or Metazoa; The kingdom contains multicellular, eukaryotic organisms having ingestive type of nutrition, regular body form, internal organs, growth definite but diffused, occurrence of tissue and organ system level of organisation, presence of nervous, sensory, muscular and excretory structures. Animals are generally mobile with a few exceptions. Cells are devoid of walls, central vacuole and plastids. Vacuoles are small. Centrioles occur. Sexual reproduction is common mode of multiplication. An embryo stage is present. Kingdom animalia includes all animals of two kingdom classification except protozoa.
Taxonomic aids
Taxonomists collect specimens from the field, preserve and store the same for later verification and reference. Studies are carried out both in the field as well as inside the laboratory. Botanical gardens, herbaria, museums and zoological parks are important aids in taxanomic studies.
Herbaria
Herbaria are collections of dry, pressed and preserved plant specimens mounted on sheets. Some plant parts are also kept in preservative liquids if they cannot be dried and pressed. The herbarium sheets are arranged according to an accepted system of classification and kept in steel cabinets. Humidity of the place is controlled. Growth of pests is prevented by regular disinfection at intervals. Every institute which teaches botany has a small or large herbarium. Very large herbaria are maintained by institutes connected with plant systematics and botanical gardens. All ecotype varieties, subspecies etc. have separate herbarium sheets.
It is also practice to keep 5 - 6 herbarium sheets of each type Largest herbarium of the world is at Kew.
(i) Herbaria are extremely useful as quick refer back system for scholars involved in taxonomic studies as they provide correct and authentic identification of even unknown plants.
(ii) Herbaria maintain type specimens from which new taxa are described.
(iii) They provide information about ecology of different places. (iv) Information about wild relatives of crop plants can be collected and their location known. It is required for breeding programmes.
Equipment Required For Specimen Collection.
Pruning knife, scissors, sickle with long handle, digger, large sized magazines or newspapers, blotting papers, plant press, vasculum, polythene bags, field note book, jotter, herbarium sheets, glue, labels, preservative in bottles.
Specimen Collection and Mounting.
Excursions are planned to local and distant places. Same place should be visited at intervals. It gives information about growth of plants in different seasons, time of flowering fruiting and seed germination besides environmental conditions and human impact on the area. The whole of small plants are collected. They should have both vegetative and reproductive parts. For shrubs and trees 25 - 30 cm long twigs with leaves and flowers are collected. 5 - 6 specimens are collected of each type. Roots, underground parts, fruits, etc. are also collected. Each collected specimen is given number, its habitat and essential features recorded in field book. The specimens are either kept in vasculum, polythene bags for spreading in the evening or immediately spread over sheets of newspapers, magazine or blotting paper. Spreading is done in such a way that wrinkles or folds do not appear in leaves and floral parts. Sepals, petals, stamens, pistils, dorsal and ventral surfaces of leaves should be properly exposed. Bigger specimens are not cut but folded in the form of n or w, Magazines or newspapers are now put inside plant press. Fleshy or thick organs are collected in preservative fluid like FAA.
Sheets are changed at intervals of 1- 2 days. This ensures proper drying. Blotting papers can also be used to quicken drying. Change of paper sheets also prevents fungal infestation. 15 - 30 days are required for complete drying. Dried specimen is kept upside down on a paper sheet, glue applied over it and then it is mounted on a herbarium sheet of standard size (29 x 41 cm).
After pasting, fungicide is sprayed over the specimen - 0.1 % mercuric chloride. Alternately pesticide like DDT, naphthalene and carbon disulphide can be used.
Heavy parts (fruit and seeds) can be put in small polythene bag and attached to sheet. A label of 7 x 12 cm size is fixed over the right hand corner of the sheet.
It carries the information about locality of collection, name of collector, date and time of collection, vernacular name, English name, scientific name, name of family, etc. The sheets are then placed in metallic cupboards of herbarium, species, genus and family wise. The place should not be humid or infested with insects, etc. Control of humidity is essential for preventing decay of specimens and fungal infection. Insect repellents can prevent insect attack.
Information about flora of a place is compiled and often published, e.g., Flora of Delhi, Flora of Punjab, Flora Simlensis, Flora of British India, Flora of Indo-Gangetic plains, Flora of Malabar hill etc.
Botanical Gardens
They are large sized tracts where plants of different types and areas are grown and maintained for scientific and educational purposes. Each such plant carries a plate mentioning its scientific name, English name, local name and family name. The first botanical garden was developed by Theophrastus. Hanging Gardens of Babylon were master pieces of ancient times. The first modern day botanical garden was established in Pisa, Italy in 1543, Royal Botanical Garden, Kew in 1759 while Indian Botanical Garden Sibpur (Kolkata) was established in 1787.
Functions of botanical gardens
(i) Growing, maintaining and multiplying rare or endangered plants.
(ii) Supply seeds and plant material to research institutes.
(iii) Growing and maintaining record of local flora.
(iv) Study of live material.
(v) Ready identification of plant materials.
(vi) Acclimitation of useful exotic plants.
(vii) Research.
The largest botanical garden is Main Botanical Garden, Moscow which is spread over an area of 900 acres. Royal Botanical Garden, Kew (London) has an area of 300 acres while Indian Botanical Garden, Sibpur (Howrah) Kolkata has an area of 273 acres.
National Botanical Garden (Sikandar Bagh), Lucknow is spread in an area of 70 acres. It also houses National Botanical Research Institute (NBRI).
Some other botanical gardens of India are Lloyd Botanical Garden Darjeeling, Botanical Garden, Ootacamand and Lalbagh Gardens, Bangalore.
Museums (Gk. mouscion - temple of Muses, goddess of arts and sciences) are institutions where objects of art, antiquity and natural hitory are stored, preserved and exhibited selectively.
They are centres of research and education besides preserving the materials. Museums of natural history provide information about local flora and fauna as well as biota of other places.
Type specimens are deposited in standard museums which also become reference centres for taxonomic studies. Only those plant parts are kept in museum which can not be stored in herbaria.
Animals are kept in three forms -
preserved in chemical solutions,
skeleton and stuffed specimens.
Due to current ecological imbalance, catching, killing and preserving animals by zoology students has been discouraged. Instead, they are now asked to collect and preserve only dead animals.
The important museums of natural history are American Museum of Natural History, New York;
Natural History Museum, London;
United States National Museum, Washington;
Bird Collection Museum of Natural History, Vienna;
National Museum of Natural History (Barakhamba Road), New Delhi;
Anthropological Museum, Andaman and Nicobar Islands;
Prince of Wales Museum/Museum of Mumbai Natural History Society, Mumbai;
Museum of Arthropoda (Shaniwar Peth), Pune.
Zoological Parks
They are large enclosed areas where wild animals are kept and nourished in enclosures akin to their natural habitats. Animals kept in zoological parks and zoos (where animals are kept in caged enclosures) are used for familiarising children and others with wild animals. They are centres of study of live animals by students.
Many endangered and rare species of animals are being kept in zoological parks for captive breeding e.g., White Tiger, Californian Candor. Information about common name, zoological name, family, habitats, etc. of each animal is displayed on the outside of its enclosure.
India has some 200 zoological parks being supervised by a Central Zoo Authority.
Each big zoolgical park also has an aviary where birds are kept. A large serpentarium is maintained in Chennai while large sized aquaria are maintained in some places (e.g., Mumbai).
Keys (Taxonomic Keys)
They are artificial analytical devices in the form of dichotomic table of alternate characteristics which are used in identification of class, order, family, genus and species. Separate taxanomic keys are required for identification of each category. Taxonomic keys are of two types, indented (= Yoked) and bracketed.
(i) Indented or Yoked Key. Here there is a sequence of two or more alternate characteristics from which selection or choice is to be made through selection and elimination. (ii) Bracketed Key. The key c0e<; not separate contrasting characters by subdividing them but instead give them numbers in brackets.
Monograph
It is a book or essay which gives comprehensive account of all the available information about a genus, family or higher category (or any other particular subject) of grouping at the time of its publication. It is a highly useful taxanomic aid.
Manual It is a hand book providing complete compiled information about a particular area with all the families, genera, species and keys for their identification.