Biodiversity is defined as ‘the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems’ – United Nations Earth Summit (1992).

• In our biosphere immense diversity (or heterogeneity) exists not only at the species level but at all levels of biological organization ranging from macromolecules within cells to biomes.
• According to IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million.
• More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total.
• Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total.
• India accounts for nearly 7% of recorded species.
• Largest biodiversity is found in Amazon rain forest on earth.

Why Tropic Account Greater Biological Diversity?

1. Speciation: It is function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years.
2. Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialization and lead to a greater species diversity.
3. More solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

Protection of water resources + Soils formation and protection + Nutrient storage and recycling + Pollution breakdown and absorption + Contribution to climate stability + Maintenance of ecosystems + Recovery from unpredictable events.

1. Habitat loss and Fragmentation: Habitat loss due to pollution, breaking of large habitats into small fragments due to various human activities, mammals and birds requiring large territories, animals with migratory habitat are badly affected, leading to population decline.
2. Over Exploitation: Humans have always depended on nature for food and shelter, but whgen ‘need’ turns to ‘greed’. it leads to over exploitation.
3. Alien Species Invasions: Alien species are species that occur outside their natural range. These species when turn invasive and cause decline or extinction of indigenous species. Ex- like water hyacinth, prosopis juliflora, lantana camara etc.
4. Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.

• India, a mega diverse country with only 2.4% of the world’s land area, accounts for 7-8% of all recorded species, including over 45,000 species of plants and 91,000 species of animals.
• The country’s diverse physical features and climatic conditions have resulted in a variety of ecosystems such as forests, wetlands, grasslands, desert, coastal and marine ecosystems.
• Four of 34 globally identified biodiversity hotspots: The Himalayas, the Western Ghats, the North-East, and the Nicobar Islands, can be found in India.
• In terms of species richness, India ranks seventh in mammals, ninth in birds and fifth in reptiles.

Insectivorous Plants: Plants are specialized in trapping insects. This is an adaptability mechanism of plant in nutrient poor soil.

• Migration refers to the regular, recurrent and cyclical seasonal movement of birds from one place to other. The distance of migration ranged from short distance to thousands of kilometers. But at the end of period, birds will eventually return to the original place.
• Reasons for migration: To avoid extreme climatic condition + To manage food shortage + To manage shortage of water + To have a better breeding conditions + Less competition for safe nesting places.

• Nanda Devi national park (Uttarakhand) – Status- World Heritage Site by UNESCO in 1988 (Nanda Devi National Park + Valley of Flowers National Park) together makes – Nanda Devi Biosphere Reserve and this reserve is recognized as UNESCO World Network of Biosphere Reserves since 2004. Species – Asiatic black bear, snow leopard, brown bear and blue sheep etc
• Dehing Patkai Elephant Reserve (Assam) – Why in news? National Board for Wild Life (NBWL) has recommended coal mining in a part of this reserve.
• Panna Tiger Reserve (Madhya Pradesh) = New entry into world network of biosphere reserves (WNBR) under MAB Programme. Presently, there are 18 notified biosphere reserves in India of which 12 are recognized under MAB Program.
• Eravikulam National Park (Kerala) à It houses the special Neelakurinji flowers Strobilantheskunthianam) that bloom once every 12 years. The park holds the largest viable population of the endangered NilgiriTahr.
• Gorumara National Park = West Bengal
• Dehing Patkai Wildlife Sanctuary (Assam): – Referred as ‘The Amazon of East’
• Melghat Tiger Reserve (Maharashtra)
• India’s 1st Lichen Park (Uttarakhand)