What are the major causes of loss of biodiversity? Explain each with an example.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Open with the problem. Species are going extinct 100 to 1,000 times faster than in pre-human times, mainly because of humans.
2 · Explain habitat loss and fragmentation. The most important cause: rain forests shrank from over 14% to no more than 6% of land; fragmentation harms wide-ranging and migratory animals.
3 · Explain over-exploitation. Greed: Steller's sea cow and the passenger pigeon; over-harvested marine fish.
4 · Explain alien species invasions. The Nile perch in Lake Victoria; Parthenium, Lantana and water hyacinth; the African catfish in Indian rivers.
5 · Explain co-extinctions. A host fish and its parasites; a plant and its co-evolved pollinator.
6 · State the effects. Lower plant production, lower resistance to drought, more variable pest and disease cycles.
7 · Link to real life. Water hyacinth in Indian lakes and Lantana in our forests show alien invasion close to home.
8 · Close in one line. So the evil quartet, all driven by humans, explains the sixth extinction.
Scoring tip: Learn the evil quartet as four headings, each with one textbook example. That alone can carry four of the five marks.
