Chapter 13 — Biodiversity and Conservation

Chapter 13 of the Class 12 Biology NCERT textbook, "Biodiversity and Conservation", explains 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.

• Levels of biodiversity — Biodiversity spans genetic diversity within a species, species diversity within a region, and ecological diversity of habitats, capturing variety at every level of biological organisation from genes to whole ecosystems.
• Global patterns of diversity — Species richness peaks in the tropics and falls toward the poles, and though only a fraction of species are described, India — with a small land area — is a mega-diversity nation holding a large share of global species.
• Causes of biodiversity loss — Extinction rates now run far above natural levels, driven by the 'Evil Quartet' — habitat loss, over-exploitation, alien species invasions, and co-extinctions — which together threaten the planet's biological wealth.
• Conservation strategies — Species are safeguarded either in situ, protecting them in natural habitats through hotspots, national parks, and biosphere reserves, or ex situ, using zoos, seed banks, and cryopreservation to save threatened forms.

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.