Biodiversity and Conservation — BIOLOGY STD 12 Science — Question

Under this category, biological species are included which were alive in the recent past but are now no longer present in their habitat and their existence has ended in other habitats also, that is, it has become extinct from the biosphere. Once extinct, specific organisms of any species can never be obtained. Man has been hunting various terrestrial, aquatic and terrestrial animals on a large scale, as a result of which many animal species have become extinct forever from the biosphere due to human activities. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. The recently extinct species include Dodo of Mauritius, Quega of Africa, Thai Laysan of Australia, Steller sea cow of Russia and three sub-species of tiger in Bali; Java and Caspian. The last 20 years alone have witnessed disappearance of 27 species. Careful analysis of records that extinction across Texas are not random some groups like amphibians appear to be more vulnerable to extinction, adding to the grim scenario of extinction is the fact that more than 15500 species worldwide are facing the threat of extinction. Presently 12% of all birds species, 23% of all mammal species, 32% of all amphibian species and 31% of all gymnosperm is species in the world face the threat of extinction. The species included in this category in India are Indian crocodile, Godavan, Indian sarus, Hornbill, Marigold, Bear and Son bird etc. which have become extinct.