UPSC Prelims 2014 Q13: Science & Technology – Biology
Which of the following phenomena might have influenced the evolution of organisms?
1. Continental drift
2. Glacial cycles
Select the correct answer
using the code given below.
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (c) Both 1 and 2
Explanation
Phenomena that influenced the evolution of organisms
| Phenomenon | Influenced evolution? | How |
|---|---|---|
| 1. Continental drift | Yes | Land masses split and moved apart, isolating populations, which then evolved separately |
| 2. Glacial cycles | Yes | Ice ages changed climate and sea level, forcing species to adapt, move or die out |
Examples:
| Evidence | Explanation |
|---|---|
| Marsupials in Australia | Evolved in isolation after the continent drifted away |
| Similar fossils in South America and Africa | The two were once joined in Gondwanaland |
| Woolly mammoth | Adapted to cold of the ice ages, then died out |
| Land bridges in ice ages | Low sea level let animals and humans cross between continents |
Geographical isolation is a main driver of new species (speciation).
Answer: (c) Both 1 and 2.
Why each option is right or wrong
- (a) Incorrect. Glacial cycles also shaped the evolution of organisms.
- (b) Incorrect. Continental drift also shaped it, by isolating populations.
- (c) CORRECT. Both continental drift and glacial cycles influenced the evolution of organisms.
- (d) Incorrect. Both phenomena played a part.
Key point
Continental drift isolates populations (marsupials of Australia); glacial cycles change climate and sea level. Both drive adaptation and speciation.
Remember
Drift isolates; ice ages select.
Common mistakes
- Thinking evolution is driven only by biological factors.
- Forgetting that isolation produces new species.
- Not linking ice ages to extinctions and migrations.
Exam tip
Anything that changes habitat or isolates groups can influence evolution.
Sources
- NCERT Class XII — Biology (Evolution)
- NCERT Class XI — Fundamentals of Physical Geography, Ch 4 (Distribution of Oceans and Continents)