UPSC Prelims 2017 · GS Paper I
Question 21: Environment and Ecology
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 :
AnswerUPSC’s answer is (c).
Butterflies are pollinators of many plants, so a huge fall in their numbers would hurt the pollination of some of them (Statement 1). They are also prey and hosts in food webs, so wasps, spiders and birds that feed on or parasitise butterflies and their caterpillars would decline too (Statement 3). Nothing links fewer butterflies to a drastic rise in fungal infections of crops, so Statement 2 is unsupported. Remember: loss of a species hits both the plants it serves and the animals that feed on it.
- 1. Butterflies pollinate some plants, so pollination would suffer.
- 2. No direct link between butterfly decline and fungal infections of crops.
- 3. Predators and parasites of butterflies and caterpillars would decline.
How you could have got this
- If you were sure statement 2 is not correct, (b) and (d) go: each of them includes 2.
What you needed to know: No direct link between butterfly decline and fungal infections of crops.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Predators and parasites of butterflies and caterpillars would decline.
Only (c) is left. You didn’t need statement 1.
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) Incomplete: the effect on wasps, spiders and birds (3) also follows.
- (b) Wrong: statement 2, a rise in fungal infections, has no clear link to butterfly decline.
- (c) Right: pollination and food-web effects follow; the fungal claim does not.
- (d) Wrong: statement 2 is not a likely consequence.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2017, General Studies Paper I, Series A. The paper on upsc.gov.in.