UPSC Prelims 2002 · General Studies
Question 43: Science and Technology
In the context of the organic evolution, the loss of limbs of snakes is explained by the phenomenon of
AnswerThe answer is (a).
The given answer explains the loss of limbs in snakes by the Lamarckian idea of use and disuse of organs: limbs that are not used for burrowing or gliding through grass dwindle over generations. It is the textbook illustration of that principle, alongside the giraffe's neck. Modern biology explains the loss instead by natural selection acting on changes in developmental genes, not by inheritance of acquired traits.
Why each option is right or wrong
- (a) Right as given: Lamarck's use and disuse is the stock explanation for limb loss in snakes.
- (b) Adaptation to burrowing is a reason, not the named phenomenon.
- (c) Natural selection is the modern explanation, but the textbook phenomenon asked for is disuse.
- (d) Inheritance of acquired characters is Lamarck's companion idea; the loss itself is attributed to disuse.
Worth knowing: Modern biology explains limb loss in snakes by natural selection acting on changes in developmental genes, so (c) can be argued; the key follows the Lamarckian textbook example.
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.