BIODIVERSITY 
The term Biodiversity was first coined by Walter rosen. The variety of living organisms is enormious and shows extreme diversity. Presently, the known and described number of spcies of all organisms on the earth is between 1.7 and 1.8 million, which is fewer than 15% of the actual number. It is predicted that the number of total species varies from 5 to 50 million. Majority of them are through to occur in the unexplored tropical rain forest and underwater coral reefs of tropical seas. The most exciting question of Biodiversity is that more than 70% of all species are animals while plants account for only 22%. Amongst animals, insects are the most numerous with previous estimate of 7 out of 10 and present estimate of 8 out of 10 animals. Further the Knowledge about protists, archaea, bacteria and viruses is quite fragmentary. Destruction of tropical unexplored forest and corals reefs may make species extrict before coming light. Basides there is fragmentary reports of the past organism as fossils in the rocks. Its is assumed that the extinct species may exceed the living ones by 50-100 times. Such a large number of living and extinct organism can not be studied without a proper universal system of nommenclature, Identification and classification.
In an ecosystem the variations observed among the members of species, the differences between the different species in the co-existing organisms of a habitat and even the differences between the ecosystem are considered as biodiversity of a habitat extends from the inner molecular features to unit organism to even population, community, ecosystem, biosphere. In the conference of rio-De-zanerio under the title biological diversity a defination of biodiversity was proposed. According to defination, biodiversity represents the variation among the organism with respect to species, community or ecosystem as expressed in all types of ecosystem either aquatic or terrestrial.
Types of biodiversity
considering the wide dimension of the defination of biodiversity.it may be classified into three types- as 1. Genetic diversity 2. Species diversity 3. Ecosystem diversity
1.Genetic Diversity : The variation of genes within species i.e., the genes and their alleles present in a particular organism is called genetic diversity.The origin of new species depends on genetic variation.So genetic variation help is species diversity.
2.species Diversity : The variety of species livings in a geographical are a known as species per unit area is know as species richness. Greater the species richness, greater is the species diversity.
3.Ecosystem diversity : different types of living entities and various abiotic components together constitude the features of an ecosystem. As without organism an ecosystem is impossible, the variation among the ecosystem are also impoetant. Because of this reason ecosystem diversity also becomes the measures of biodiversity. In consideration to communities in the ecosystem.
ecological diversity includes Alpha diversity. Beta diversity and gamma diversity. This diversity may be in following parameters :
1. Alpha Diversity : Alpha diversity is represented by the number of species in a speciefied area. The diversity shows within community and depends on the species richness and evenness. A lot of competitions and interaction are observed among members of the same community.
2. Beta Diversity: The change in habitat due to presence of different microhabitats, niches and environmental condition, the biodiversity which appears in a range of communities due to represented of speies is called beta diversity.
3. Gamma Diversity : Gamma diversity is represented by the variation of habitat of the organism in a large geographical area. It is the total diversity including alpha and beta diversity.
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