Biology is an important branch of science dealing with the study of life. It is difficult to define life. But it is easy to discriminate living things from non–living things. On this basis life is defined as a physicochemical entity exhibiting growth, movement, irritability and reproduction. Biology includes two branches, namely Botany and Zoology. Botany deals with the study of plants and Zoology deals with the study of animals.
# (i) Order in Diversity : In spite of its vastness and diversity, the Animal World is not a disorderly junk or animals, as it appears to us when casually viewed, but it has a definite grading order in its diversity. That is way, we can segregate all animals species into small and large groups, called taxa (singular, taxon), on basis of their comparative similarities and dissimilarities. For example, fishes are of so many diverse varieties or species, yet all possess may important common features and, hence, belong to a common group – Pisces. Similarly, all frog like animals forms belong to Amphibia, all lizard like forms to Reptilia, all birds to Aves, and all animals possessing hairs and mammary glands, like man, to Mammalia, Further, the Pisces, Amphibia, Reptilia, Aves and Mammals are, though, strikingly different groups of animal forms but, because of certain basic similarities, such as possession of a cartilaginous or bony endoskeleton, these groups qualify for a larger common group of taxon – the Vertebrata.
Orderly grouping of species in large and small groups or taxa on basis of similarities and dissimilarities is called classification. Proper characterization and identification of species and assigning them suitable scientific names is necessary pre–requisite for classification. This is called nomenclature of species. The study of nomenclature and classification, including the laws, principles and methods of both, is called Taxonomy or Systematics. The basic unit of taxonomy is species “Father of Taxonomy” Carolus Linnaeus.
# (ii) Objectives of Classification : Academic convenience has been the foremost objective of classification. None can study all animal types separately but, by studying a given type, one gains a fairly good basic knowledge of the whole group or groups to which this types belongs in the scheme of classification. Another, more important objective of classification is to readily reveal the basic or phylogenetic relationships between the various types of animal forms.
# (iii) Brief History of Taxonomy : Ancient people used to classify animals on such criteria as harmful or harmless, flying or non flying, edible or non edible, useful or useless, and so on. The famous Greek Philosopher, Aristotle (384-322 B.C), recognized and “Father of Zoology”, was the first scientist to classify the known animal forms on basis of natural resemblance and dissimilarities. He divided these into two main groups :
(a) Anaima : All animal forms devoid of red blood, such as sponges, cnidaria, mollusca, arthropoda, echinodermata, etc., and
(b) Enaima : All animal forms having red blood, viz., the present-day vertebrates. He further divided these into two subgroups
(1) Vivipara : Those that give birth to young ones such as man, dogs, cows, buffaloes, etc., and
(2) Ovipara : Those that lay eggs, such as frogs and toads, lizards, snakes, birds, etc.
Pliny (77 years after Christ – A.D.) classified animals into two categories – those that fly and those that do not fly. Long after this, in the 17th century, the English naturalist John Ray (1693) first clearly defined a “species” and introduced this term Eventually, the Swedish Botanist, Carolus Linnaeus. In the tenth edition (1758) of his book. “Systema Naturae”, he classified the known 4236 animal species, and the system he employed for this laid the foundation of modern classification. In this edition, he also devised a method of “Binomial Nomenclature” for naming the species as described below. Linnaeus is therefore, recognized as “Father of Modern Taxonomy”.
# (iv) Characterization of Species : Species is the smallest basic unit of classification. Its proper characterization is, therefore, of vital importance for a “Natural” scheme of classification. Identifying species on basis of reproduction, John Ray (1693) considered all individuals produced by parents of the same type as members of the same species. Linnaeus and some others distinguished species merely on the basis of structure. Mayr (1942) defined species as a “population of interbreeding individuals. According to the latest views, a species can be characterized as follows
(a) Each species is a population of interbreeding individuals.
(b) The whole population of each species has a common “gene pool” with a free assortment of genes, i.e., “gene flow”.
(c) Populations of a species inhabiting different geographical areas are in a continuous process of adapting to the conditions of their respective environments.
# (v) Nomenclature of Species– Common or Vernacular names : Animal types, known to common man, are called, in different countries, by local vernacular names. For example, the common house sparrow is called “Goraiya” in India, “Sparrow” in England and America, “Haussperling”.
(a) Binomial nomenclature : In the tenth edition of his “Systema Naturae”, Linnaeus adopted a new method of naming the species. Just as it is customary in certain castes in our country to add father's name with the names of the sons, Linnaeus assigned, for each species, a dual Latin name in which the second name was the actual name of the species, while the first one was that of the genus under which he had included related species.
For example, he assigned the name of Passer domesticus to house sparrow, Homo sapiens to man, Canis familiaris to dog and so on. This scheme of nomenclature is known as “binomial nomenclature”. It was gradually adopted by biologists all over the world, and the specific names, so assigned, were recognized as “International Scientific Names” as against the common or vernacular names. The term Biological nomenclature is applicable to both animals and plants Carolus linnaeus proposed the Binomial nomenclature.
(b) Trinomial nomenclature : Biologists observed that different populations of the same species, effectively isolated for a long time due to geographical barriers, gradually drift from each other in certain genetic characteristics, constituting smaller groups, called subspecies, Till the members of different populations can interbreed, they belong to the same species, but when they can no more interbreed, they become separate species. Naming of subspecies is called “trinomial nomenclature”, because, in this, a third name is added to the name of the species. For instance, the common crow, Corvus splendens, has local populations in India, Burma and Ceylon, recognized as subspecies and named respectively as C. splendens splendens, C. Splendens insolens and C. splendens protegatus.
(c) International rules of nomenclature : In order that each species be known by a common scientific name all over the world, and no name be used for more than one species, the International Congress of Zoology adopted, in 1901, a set of International Rules of Zoological Nomenclature for naming animal species in accordance with the “Binomial Nomenclature” of Linnaeus. These rules were later revised in 1961. According to these, the first, generic name in the binomial name of a species, shared by all other related species, should be a single word beginning with a capital letter, while the second, specific name, should be a single or compound word beginning with a small letter; the full name should be latinized and printed in italics.
# (vi) Principles of Classification : After dividing the then known species under several genera, Linnaeus himself segregated all genera under six classes, viz., Mammalia, Aves, Amphibia, pisces, Insecta and Vermes, merely on morphological grounds. As better criteria for classification were adopted during the 18th century, six main grading categories, ranks or taxa were proposed, and these were also later adopted by Linnaeus (1758) :
(1) Species, (2) Genus, (3) Family, (4) Order, (5) Class, (6) Phylum
As is clear from the sequence or hierarchy of these groupings or taxa, two or more related species, evolved from a common ancestor according to the concept of “Organic Evolution”, form a common genus related genera constitute a family; related families are combined into an order; orders into a class, and classes into a phylum. Term “Phylum” in animal classification was coined by G.L cuvier.
# (vii) Artificial vs Natural classifications : Since earlier schemes of classification, like the one presented even by Linnaeus, used to be based on superficial resemblance, these were incapable or revealing the natural relationships of the species concerned. Hence, these were artificial schemes of classification. According to the universally accepted concept of “Organic Evolution”, all species, existing today, evolved in the remote past, from common ancestors as a result of adaptive radiation or divergence. Hence, all species are related to each other closely or remotely, and can be segregated into larger and smaller groups according to the extent of this phylogenetic relationship. In contrast to artificial classifications, a natural classification, thus, already exists within the framework of the “natural order” of the animal world itself, only waiting to be fully discovered. Evidently, a natural scheme of classification must be based upon criteria which reflect the fundamental or genetic, i.e., blood relationships of the species concerned. To cite a few, the symmetry, organization and segmentation of body, types of body cavities and appendages, sexual characteristics and development, cellular specialization, biochemistry and genetics, habits and habitat, larval stages, etc., are criteria of this category. A scheme of classification based upon these criteria will, thus, be a “Natural, or Phylogenetic, or Genealogical classification”.
Biology is an important branch of science dealing with the study of life. It is difficult to define life. But it is easy to discriminate living things from non–living things. On this basis life is defined as a physicochemical entity exhibiting growth, movement, irritability and reproduction. Biology includes two branches, namely Botany and Zoology. Botany deals with the study of plants and Zoology deals with the study of animals.
# (i) Order in Diversity : In spite of its vastness and diversity, the Animal World is not a disorderly junk or animals, as it appears to us when casually viewed, but it has a definite grading order in its diversity. That is way, we can segregate all animals species into small and large groups, called taxa (singular, taxon), on basis of their comparative similarities and dissimilarities. For example, fishes are of so many diverse varieties or species, yet all possess may important common features and, hence, belong to a common group – Pisces. Similarly, all frog like animals forms belong to Amphibia, all lizard like forms to Reptilia, all birds to Aves, and all animals possessing hairs and mammary glands, like man, to Mammalia, Further, the Pisces, Amphibia, Reptilia, Aves and Mammals are, though, strikingly different groups of animal forms but, because of certain basic similarities, such as possession of a cartilaginous or bony endoskeleton, these groups qualify for a larger common group of taxon – the Vertebrata.
Orderly grouping of species in large and small groups or taxa on basis of similarities and dissimilarities is called classification. Proper characterization and identification of species and assigning them suitable scientific names is necessary pre–requisite for classification. This is called nomenclature of species. The study of nomenclature and classification, including the laws, principles and methods of both, is called Taxonomy or Systematics. The basic unit of taxonomy is species “Father of Taxonomy” Carolus Linnaeus.
# (ii) Objectives of Classification : Academic convenience has been the foremost objective of classification. None can study all animal types separately but, by studying a given type, one gains a fairly good basic knowledge of the whole group or groups to which this types belongs in the scheme of classification. Another, more important objective of classification is to readily reveal the basic or phylogenetic relationships between the various types of animal forms.
# (iii) Brief History of Taxonomy : Ancient people used to classify animals on such criteria as harmful or harmless, flying or non flying, edible or non edible, useful or useless, and so on. The famous Greek Philosopher, Aristotle (384-322 B.C), recognized and “Father of Zoology”, was the first scientist to classify the known animal forms on basis of natural resemblance and dissimilarities. He divided these into two main groups :
(a) Anaima : All animal forms devoid of red blood, such as sponges, cnidaria, mollusca, arthropoda, echinodermata, etc., and
(b) Enaima : All animal forms having red blood, viz., the present-day vertebrates. He further divided these into two subgroups
(1) Vivipara : Those that give birth to young ones such as man, dogs, cows, buffaloes, etc., and
(2) Ovipara : Those that lay eggs, such as frogs and toads, lizards, snakes, birds, etc.
Pliny (77 years after Christ – A.D.) classified animals into two categories – those that fly and those that do not fly. Long after this, in the 17th century, the English naturalist John Ray (1693) first clearly defined a “species” and introduced this term Eventually, the Swedish Botanist, Carolus Linnaeus. In the tenth edition (1758) of his book. “Systema Naturae”, he classified the known 4236 animal species, and the system he employed for this laid the foundation of modern classification. In this edition, he also devised a method of “Binomial Nomenclature” for naming the species as described below. Linnaeus is therefore, recognized as “Father of Modern Taxonomy”.
# (iv) Characterization of Species : Species is the smallest basic unit of classification. Its proper characterization is, therefore, of vital importance for a “Natural” scheme of classification. Identifying species on basis of reproduction, John Ray (1693) considered all individuals produced by parents of the same type as members of the same species. Linnaeus and some others distinguished species merely on the basis of structure. Mayr (1942) defined species as a “population of interbreeding individuals. According to the latest views, a species can be characterized as follows
(a) Each species is a population of interbreeding individuals.
(b) The whole population of each species has a common “gene pool” with a free assortment of genes, i.e., “gene flow”.
(c) Populations of a species inhabiting different geographical areas are in a continuous process of adapting to the conditions of their respective environments.
# (v) Nomenclature of Species– Common or Vernacular names : Animal types, known to common man, are called, in different countries, by local vernacular names. For example, the common house sparrow is called “Goraiya” in India, “Sparrow” in England and America, “Haussperling”.
(a) Binomial nomenclature : In the tenth edition of his “Systema Naturae”, Linnaeus adopted a new method of naming the species. Just as it is customary in certain castes in our country to add father's name with the names of the sons, Linnaeus assigned, for each species, a dual Latin name in which the second name was the actual name of the species, while the first one was that of the genus under which he had included related species.
For example, he assigned the name of Passer domesticus to house sparrow, Homo sapiens to man, Canis familiaris to dog and so on. This scheme of nomenclature is known as “binomial nomenclature”. It was gradually adopted by biologists all over the world, and the specific names, so assigned, were recognized as “International Scientific Names” as against the common or vernacular names. The term Biological nomenclature is applicable to both animals and plants Carolus linnaeus proposed the Binomial nomenclature.
(b) Trinomial nomenclature : Biologists observed that different populations of the same species, effectively isolated for a long time due to geographical barriers, gradually drift from each other in certain genetic characteristics, constituting smaller groups, called subspecies, Till the members of different populations can interbreed, they belong to the same species, but when they can no more interbreed, they become separate species. Naming of subspecies is called “trinomial nomenclature”, because, in this, a third name is added to the name of the species. For instance, the common crow, Corvus splendens, has local populations in India, Burma and Ceylon, recognized as subspecies and named respectively as C. splendens splendens, C. Splendens insolens and C. splendens protegatus.
(c) International rules of nomenclature : In order that each species be known by a common scientific name all over the world, and no name be used for more than one species, the International Congress of Zoology adopted, in 1901, a set of International Rules of Zoological Nomenclature for naming animal species in accordance with the “Binomial Nomenclature” of Linnaeus. These rules were later revised in 1961. According to these, the first, generic name in the binomial name of a species, shared by all other related species, should be a single word beginning with a capital letter, while the second, specific name, should be a single or compound word beginning with a small letter; the full name should be latinized and printed in italics.
# (vi) Principles of Classification : After dividing the then known species under several genera, Linnaeus himself segregated all genera under six classes, viz., Mammalia, Aves, Amphibia, pisces, Insecta and Vermes, merely on morphological grounds. As better criteria for classification were adopted during the 18th century, six main grading categories, ranks or taxa were proposed, and these were also later adopted by Linnaeus (1758) :
(1) Species, (2) Genus, (3) Family, (4) Order, (5) Class, (6) Phylum
As is clear from the sequence or hierarchy of these groupings or taxa, two or more related species, evolved from a common ancestor according to the concept of “Organic Evolution”, form a common genus related genera constitute a family; related families are combined into an order; orders into a class, and classes into a phylum. Term “Phylum” in animal classification was coined by G.L cuvier.
# (vii) Artificial vs Natural classifications : Since earlier schemes of classification, like the one presented even by Linnaeus, used to be based on superficial resemblance, these were incapable or revealing the natural relationships of the species concerned. Hence, these were artificial schemes of classification. According to the universally accepted concept of “Organic Evolution”, all species, existing today, evolved in the remote past, from common ancestors as a result of adaptive radiation or divergence. Hence, all species are related to each other closely or remotely, and can be segregated into larger and smaller groups according to the extent of this phylogenetic relationship. In contrast to artificial classifications, a natural classification, thus, already exists within the framework of the “natural order” of the animal world itself, only waiting to be fully discovered. Evidently, a natural scheme of classification must be based upon criteria which reflect the fundamental or genetic, i.e., blood relationships of the species concerned. To cite a few, the symmetry, organization and segmentation of body, types of body cavities and appendages, sexual characteristics and development, cellular specialization, biochemistry and genetics, habits and habitat, larval stages, etc., are criteria of this category. A scheme of classification based upon these criteria will, thus, be a “Natural, or Phylogenetic, or Genealogical classification”.
