2012 CSAT, all questions

UPSC Prelims 2012 · CSAT

Question 32: Reading Comprehension

Passage – 1 · as printed by UPSC
Passage beginning “Invasions of exotic species into new…”Passage beginning “Invasions of exotic species into new…”

What can be the impact of invasion of exotic species on an ecosystem ?

  1. 1.Erosion of endemic species.
  2. 2.Change in the species composition of the community of the ecosystem.

Select the correct answer using the codes given below :

a1 only
b2 only
cBoth 1 and 2
dNeither 1 nor 2

AnswerUPSC’s answer is (c).

The passage says a few introduced species have transformed native wildlife and natural communities, and gives the case of the brown tree snake in Guam, whose raiding of nests drove ten endemic forest bird species to the brink of extinction. That is erosion of endemic species (statement 1). It also says introductions turn a hugely varied range of local communities into more uniform ones, which changes community composition (statement 2). Both effects are stated.

  • 1. Introduced species can wipe out endemics, as the snake did to endemic forest birds in Guam.
  • 2. Introductions change the make-up of local communities, making them more uniform.

How you could have got this

  1. If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.

    What you needed to know: Introduced species can wipe out endemics, as the snake did to endemic forest birds in Guam.

  2. Then, if you were sure statement 2 is correct, (a) goes: it leaves 2 out.

    What you needed to know: Introductions change the make-up of local communities, making them more uniform.

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. Statement 2 is also an impact.
  • (b) Wrong. Statement 1 is also an impact.
  • (c) Right. Both loss of endemic species and altered community composition are described.
  • (d) Wrong. Both are described.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious questionNext question

Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.