UPSC Prelims 2011 Q61: Environment & Ecology – Ecosystems & Ecology Concepts
Biodiversity forms the basis for human existence in the following ways:
1. Soil formation
2. Prevention of soil erosion
3. Recycling of waste
4. Pollination of crops
Select the correct answer using the codes given below:
- (a) 1, 2 and 3 only
- (b) 2, 3 and 4 only
- (c) 1 and 4 only
- (d) 1, 2, 3 and 4
Answer: (d) 1, 2, 3 and 4
Explanation
How biodiversity underpins human existence
Biodiversity provides several basic ecological services that human life depends on.
| Service | Verdict | Reason |
|---|---|---|
| 1. Soil formation | Correct | Microbes, fungi and organisms break down rock and organic matter into fertile soil |
| 2. Prevention of soil erosion | Correct | Plant roots and vegetation cover hold soil in place against wind and water |
| 3. Recycling of waste | Correct | Decomposers (bacteria, fungi) break down organic waste, returning nutrients to the ecosystem |
| 4. Pollination of crops | Correct | Bees, birds and insects pollinate the majority of food crops |
Ecosystem services from biodiversity:
| Point | Detail |
|---|---|
| Soil | Formation and erosion prevention |
| Nutrient cycling | Decomposers recycle waste |
| Food security | Pollinators sustain crop yields |
Answer: (d) 1, 2, 3 and 4.
Why each option is right or wrong
- (a) Incorrect. Service 4 (pollination) is also essential, so '1, 2 and 3 only' leaves out a real basis for human existence.
- (b) Incorrect. Service 1 (soil formation) is also fundamental, so excluding it is wrong.
- (c) Incorrect. Services 2 and 3 (erosion prevention, waste recycling) are also essential, so '1 and 4 only' is far too narrow.
- (d) CORRECT. All four services — soil formation, erosion prevention, waste recycling, and pollination — are basic ways biodiversity supports human existence.
Key point
Biodiversity underpins human existence through soil formation, erosion prevention, waste recycling (decomposers), AND crop pollination — all four, not a subset.
Remember
Biodiversity's basic services: soil formation, erosion prevention, waste recycling, and crop pollination — all four.
Common mistakes
- Assuming only direct food-related services (like pollination) count as basic ecosystem services.
- Underestimating the role of decomposers in nutrient/waste recycling.
- Missing that soil formation itself depends on biological activity, not just geology.
Exam tip
When a biodiversity 'basis for human existence' question lists plausible ecosystem services, 'all of the above' is usually correct.
Sources
- Millennium Ecosystem Assessment — Ecosystems and Human Well-being: Synthesis (2005)
- NCERT Class XII Biology — Biodiversity and Conservation