UPSC Prelims 2002 · General Studies
Question 11: Science and Technology
Among living organisms, which one of the following is the most responsible factor for bringing about the origin of a new species?
AnswerThe answer is (a).
A new species arises when populations stop interbreeding. Isolation, geographical or reproductive, cuts gene flow, so each population gathers its own mutations and selected traits and drifts apart until the two can no longer interbreed. Mutation supplies variation and natural selection acts on it, but without isolation they are mixed back into a single population. That is why isolation is taken as the most responsible factor in speciation.
Why each option is right or wrong
- (a) Right: isolation stops gene flow, so separated populations diverge into new species.
- (b) Mutation only supplies raw variation; it does not separate populations.
- (c) Selection acts on variation, but free interbreeding keeps the population one species.
- (d) Sexual reproduction shuffles genes within a species; it does not create a species boundary.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.