https://doi.org/10.46505/IJBI.2019.1205 Sadguru Prakash and Seema Srivastava 61 Himalayas, North-east India and Andaman Islands, and the Western Ghats. Biogeographically, India is situated at the trijunction of three realms: Afro-tropical, Indo-Malayan and Paleo-Arctic realms, and therefore, has characteristic elements from each of them. This assemblage of three distinct realms makes the country rich and unique in biological diversity. It has a great wealth of biological diversity in its forests, wetlands and in its marine areas. It is estimated that over 46,000 species of plants and 81,000 species of animals are found in India. The flowering plants comprise 15,000 species of which about 7000 species are endemic. Among the animal species diversity more than 50,000 species of insects, 4,000 molluscs, 6,500 other vertebrates, 2,546 fishes, 197 amphibians, 408 reptiles, 1224 birds23% island species are becoming endangered and hence economic loss in the tourism sector. Inland water ecosystem: It includes lotic and lentic fresh water ecosystem and comprising 0.8% of the earth's surface, but support 6% of the total species. They are rich source of food, income, employment and biodiversity. Changing climatic conditions like rainfall and temperature lead to changes in the phenology, physiology and migration trends of some organisms like migratory fishes and birds. Forest ecosystem: One third of earth's surface is covered by forest and it is the home place of two third of all terrestrial species. They are also rich biodiversity hotspots. But half of the original forest has been cleared up till now. Green house effect has led to increase in growth of some forest,