Q21 · UPSC Prelims 2017 · Set A · Environment and Ecology

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Due to some reasons, if there is a huge fall in the population of species of butterflies, what could be its likely consequence/consequences?1.Pollination of some plants could be adversely affected.2.There could be a drastic increase in the fungal infections of some cultivated plants.3.It could lead to a fall in the population of some species of wasps, spiders and birds.Select the correct answer using the code given below:

A 1 only
B 2 and 3 only
C 1 and 3 only
D 1, 2 and 3

Correct answer: (c) 1 and 3 only

Explanation

  1. A

    1 only

    (a) 1 only. Butterflies are pollinators, so statement 1 is true, but they are also prey for wasps, spiders and birds, so 3 is true as well. 1 only is incomplete.

  2. B

    2 and 3 only

    (b) 2 and 3 only. Statement 2 — a drastic rise in fungal infections of crops solely from fewer butterflies — is not a direct ecological consequence. Not the key.

  3. C

    1 and 3 only

    (c) 1 and 3 only. Loss of butterflies can cut pollination of butterfly-visited plants and can shrink predators that eat them. Fungal epidemics are not a necessary follow-on. This is the official key.

  4. D

    1, 2 and 3

    (d) 1, 2 and 3. The fungal claim is the extra, unsupported leap.

Summary. Official key is (c) 1 and 3 only. Many wild and cultivated plants depend in part on butterfly (and moth) pollination. Butterflies sit in food webs as prey, so wasps, spiders and insectivorous birds can decline if that prey collapses. A drastic increase in crop fungal disease is not a standard, direct result of butterfly loss. Bees remain the larger pollination story; this question isolates butterflies.

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