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Class 11 Biodiversity and Conservation: cheat sheet
CBSE Social Science. The levels and value of biodiversity, why it is being lost, the IUCN categories of threatened species, and how it can be conserved.
Key ideas
- Biodiversity is the variety of life in a region at three levels: genetic, species and ecosystem diversity.
- It is richest in the tropics, which get more sunlight and water; tropical rain forests hold about half of all species.
- Biodiversity has ecological, economic and scientific roles: it cycles matter, gives food and medicines, and shows how life evolved.
- It is lost through habitat destruction, over-exploitation, pollution, exotic species, poaching and natural calamities.
- The IUCN Red List groups threatened species as endangered, vulnerable or rare.
- Conservation means protecting habitats, saving crop and livestock varieties, regulating wildlife trade and involving local people.
- Hotspots are species-rich, vulnerable areas; mega diversity centres are tropical countries such as India, Brazil, Indonesia and Madagascar.
Remember
| Species on the earth | about 10 million |
| Extinct | about 99% of all species that ever lived (1% survive) |
| Madagascar | about 85% of its plants and animals found nowhere else |
| Percentage of a total | per cent × total ÷ 100 |
| Endangered, vulnerable, rare | in danger of extinction / likely to be endangered soon / very small populations |
| India’s wildlife law | Wild Life (Protection) Act, 1972 |
Watch out
- Mixing up vulnerable (may become endangered) and rare (very few, in a small area).
- Thinking exotic species are rare local ones: they are brought in from outside.
- Saying biodiversity is richest near the poles.
Worked example
About 99 per cent of all species that ever lived are extinct. If 66,000 species of a group ever lived, how many survive and how many are extinct?
Working: 1% and 99% of 66,000
Answer: 660 survive; 65,340 are extinct
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