UPSC Prelims 2014 · GS Paper I
Question 13: Environment and Ecology
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.
AnswerUPSC’s answer is (c).
Both phenomena changed the conditions under which organisms evolved. Continental drift separated and joined landmasses, isolating populations and opening new habitats, so lineages evolved separately on different continents. Glacial cycles repeatedly changed climate and sea level, forcing species to migrate, adapt or die out and shaping which forms survived. Both are accepted influences on the evolution of organisms.
- 1. Drifting continents isolated populations and changed habitats.
- 2. Glacial cycles changed climate and sea level and shifted species ranges.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Drifting continents isolated populations and changed habitats.
- Then, if you were sure statement 2 is correct, (a) goes: it leaves 2 out.
What you needed to know: Glacial cycles changed climate and sea level and shifted species ranges.
Only (c) is left. This one needs every statement.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong. Glacial cycles also influenced evolution.
- (b) Wrong. Continental drift also influenced evolution through isolation of populations.
- (c) Right. Both continental drift and glacial cycles influenced evolution.
- (d) Wrong. Both have influenced the evolution of organisms.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2014, General Studies Paper I, Series A. The paper on upsc.gov.in.