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UPSC Prelims 2011 · Environment · Nature’s Machinery
Consider the following statements: Which of the statements given above is/are correct?
- Biodiversity is normally greater in the lower latitudes as compared to the higher latitudes.
- Along the mountain gradients, biodiversity is normally greater in the lower altitudes as compared to the higher altitudes.
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Show the answer and explanation
Answer: (c) Both 1 and 2
Both are standard gradients: diversity falls towards the poles and up a mountain.
Statement by statement
1. ✓ CORRECT Tropics have more sunlight, stable climate and long evolutionary time — the most species.
2. ✓ CORRECT Going up, temperature and growing season fall, so fewer species survive.
The idea
Going up a mountain is like travelling towards the pole: it gets colder and the growing season gets shorter. So both journeys show the same fall in the number of species.
Equator → pole: rainforest → deciduous forest → conifers → tundra → ice → Foot of mountain → peak: tropical forest → oak and pine → fir → alpine meadow → snow
The trap
Both are the classic textbook gradients.
Also know
Why the tropics are richest: more sunlight and so more plant growth; little change between seasons; and no ice ages wiped them clean, so species had a very long time to evolve.
🔒 Diversity decreases with latitude and with altitude (every ~1,000 m up ≈ several hundred km towards the pole).