BIODIVERSITY: ANIMALS

 There is enormous biological diversity!

   There are almost 8.7 million species on this earth. This number is rapidly increasing every day. This mind boggling number makes it almost impossible to study each and every day. This mind boggling number makes it almost impossible to study each and every organism individually. Therefore, scientists felt that these organisms must be grouped in some fashion into discrete categories. This not only made their job simpler but also helped to characterize them. This was beginning of a system of classification. The categorization however cants be random e.g., if we list names or words in a telephone directory or dictionary randomly, we shall never be able to find or locate a particular telephone number or meaning of a particular word. Therefore, a uniform and universal scientific system of classification was developed for the organisms.

   A taxonomist’s job didn’t get over by merely classifying the organisms; the organisms also needed a scientific name. Since the organisms are known differently at different places and their common names are used casually, it creates confusion, e.g. a silver fish is an insect and not a fish; similarly, sea mouse is not even distantly related with a mouse. Hence, it necessitated a code of naming or nomenclature. A number of attempts were made in this direction but success came to the famous Swedish naturalist Carlus Linnaeus who developed the system of Bionomial Nomenclature in his book called Systems Naturae in 1758. This distinction earned him the title of “Father of Taxonomy”.

    According to his code of nomenclature , (“Bi” meaning “two”), the name of every living organism consists of two words – the first word, referring to generic name (name of the genus ), which is common with other related forms, and the second word is species name which is unique for a particular organism. The two together specify the name of the species e.g., Homo sapiens (Man, the wise) is the scientific name of “Modern man” where Homo is the name of the genus and sapiens is the name of species

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Classification: Classification is possible because there are certain common features between related organisms but at the same time, they are also distinct from each other e.g., all snakes share certain common features and look more or less similar viz. absence of limbs, body covered with scales, forked tongue, etc. but at the same time a cobra can be easily differentiated from a viper or a krait.

   The original system of classification was artificial and based on few characters only. Therefore, it was rejected and since then continuous attempts have be made to improve it and make it more scientific and universally acceptable. This led to the development of the present taxonomic system proposed by R.H. whittaker and known by his name as Whittaker’s Five-Kingdom System of Classification (1969). Here, living organisms are divided into following five kingdoms:

(1)    Monera (prokaryotes)

(2)    Protista (a diverse kingdom consisting mostly of unicellular organisms both plants and animals)

(3)    Plantae (Plants)

(4)    Fungi and

(5)    Animalia (animals)

 However, when phylogenies were worked out on the basis of genetic data, it was found that prokaryotes we markedly different not only from eukaryotes but also from each other. This led biologists to modify the present system and adopt a Three-Domain System.

 

The Domains are a taxonomic level higher than the kingdom level. Currently this system is more popular.