UPSC Prelims 2011 Q96: Environment & Ecology – Biodiversity & Conservation
Consider the following statements:
1. Biodiversity is normally greater in the lower latitudes as compared to the higher latitudes.
2. Along the mountain gradients, biodiversity is normally greater in the lower altitudes as
compared to the higher altitudes.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (c) Both 1 and 2
Explanation
Biodiversity gradients: latitude and altitude
Biodiversity follows well-documented patterns along both latitude and mountain elevation.
| Statement | Verdict | Reason |
|---|---|---|
| 1. Biodiversity is greater at lower latitudes than higher latitudes | Correct | The tropics (low latitudes) host far greater species diversity than polar/temperate (high latitude) regions, a well-known ecological pattern |
| 2. Along mountains, biodiversity is greater at lower altitudes than higher altitudes | Correct | Similarly, lower mountain elevations (warmer, more productive) generally support greater biodiversity than colder, harsher high altitudes |
Biodiversity gradients:
| Point | Detail |
|---|---|
| Latitude gradient | Tropics > temperate > polar diversity |
| Altitude gradient | Lower slopes > higher slopes diversity |
| Underlying driver | Warmer, more stable, productive conditions support more species |
Answer: (c) Both 1 and 2.
Why each option is right or wrong
- (a) Incorrect. Statement 2 (altitude gradient) is also correct, so '1 only' is incomplete.
- (b) Incorrect. Statement 1 (latitude gradient) is also correct, so '2 only' is incomplete.
- (c) CORRECT. Both the latitude gradient (tropics richer than poles) and the altitude gradient (lower slopes richer than peaks) are well-established biodiversity patterns.
- (d) Incorrect. Since both statements are accurate, 'neither' is wrong.
Key point
Biodiversity is generally greater at LOWER latitudes (tropics) than higher latitudes, AND greater at LOWER altitudes than higher altitudes along mountains — both gradients hold true.
Remember
Biodiversity is greater at lower latitudes AND lower altitudes — both gradients point toward warmer, lower-elevation zones being richer.
Common mistakes
- Assuming only the latitude gradient, and not the parallel altitude gradient, is a real ecological pattern.
- Confusing 'higher' with 'more diverse' when it's actually the opposite for both latitude and altitude.
- Not connecting warmer, more stable conditions to greater species richness.
Exam tip
Biodiversity decreases as you go toward the poles (latitude) OR toward mountain peaks (altitude) — both gradients run the same direction.
Sources
- NCERT Class XII Biology — Biodiversity and Conservation (patterns of biodiversity: latitudinal gradients)
- Eugene P. Odum — Fundamentals of Ecology (species diversity gradients)