Chapter 13 — Biodiversity and Conservation

NCERT Class 12 Biology Chapter 13 covers Biodiversity and Conservation, explaining the three levels of biodiversity (genetic, species, ecological), patterns of species distribution, causes of biodiversity loss, and strategies for conservation including in situ and ex situ methods.

Biodiversity refers to the combined diversity at all levels of biological organisation, a term popularised by sociobiologist Edward Wilson. According to IUCN (2004), over 1.5 million species have been described, with global estimates placed at about 7 million by Robert May. India, occupying only 2.4% of the world's land area, accounts for 8.1% of global species diversity, making it one of 12 mega diversity countries. Species richness is highest in the tropics and decreases towards the poles. The four major causes of biodiversity loss — called the 'Evil Quartet' — are habitat loss, over-exploitation, alien species invasions, and co-extinctions. Conservation strategies include in situ (biodiversity hotspots, national parks, biosphere reserves) and ex situ (zoological parks, seed banks, cryopreservation) approaches.

1. 01Biodiversity exists at three levels: genetic diversity (e.g., India has 50,000+ strains of rice), species diversity (e.g., Western Ghats vs Eastern Ghats amphibians), and ecological diversity (e.g., India's deserts, rain forests, coral reefs).
2. 02Global species diversity is estimated at about 7 million by Robert May; only about 1.5 million have been formally described as of IUCN 2004.
3. 03Species richness follows a latitudinal gradient, decreasing from the tropics toward the poles; the Amazonian rain forest harbours the greatest biodiversity on Earth.
4. 04Current species extinction rates are 100 to 1,000 times faster than pre-human rates; the 'Evil Quartet' of causes comprises habitat loss, over-exploitation, alien species invasions, and co-extinctions.
5. 05In situ conservation protects species in their natural habitat through biodiversity hotspots (34 worldwide, three covering India), biosphere reserves, national parks, and sacred groves.
6. 06Ex situ conservation removes threatened species from their habitat for protection via zoos, botanical gardens, seed banks, cryopreservation, and tissue culture propagation.