2021 GS Paper I, all questions

UPSC Prelims 2021 · GS Paper I

Question 61: Environment and Ecology

The vegetation of savannah consists of grassland with scattered small trees, but extensive areas have no trees. The forest development in such areas is generally kept in check by one or more or a combination of some conditions. Which of the following are such conditions?

  1. 1.Burrowing animals and termites
  2. 2.Fire
  3. 3.Grazing herbivores
  4. 4.Seasonal rainfall
  5. 5.Soil properties

Select the correct answer using the code given below.

a1 and 2
b4 and 5
c2, 3 and 4
d1, 3 and 5

AnswerUPSC’s answer is (c).

Savannas are grasslands with scattered trees, and tree growth is held back by repeated fire, which kills seedlings and saplings, by grazing and browsing herbivores that damage young trees, and by strongly seasonal rainfall with a long dry season. UPSC does not count burrowing animals, termites or soil properties among the main checks. Remember: fire, herbivores and seasonal rainfall keep the savanna open.

  • 1. Burrowing animals and termites are not counted as the main checks on tree growth.
  • 2. Fire kills tree seedlings and favours grasses.
  • 3. Grazing and browsing herbivores damage young trees.
  • 4. A long dry season limits tree growth.
  • 5. Soil properties are not counted among the main checks.

How you could have got this

  1. If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.

    What you needed to know: Burrowing animals and termites are not counted as the main checks on tree growth.

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

    What you needed to know: Fire kills tree seedlings and favours grasses.

Only (c) is left. You didn’t need statements 3, 4 or 5.

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: it takes burrowing animals, termites and fire, and misses grazing and seasonal rainfall.
  • (b) Wrong: soil properties are not counted, and fire and grazing are missing.
  • (c) Right: fire, grazers and seasonal rainfall keep trees in check.
  • (d) Wrong: burrowers and soil properties are not counted by UPSC.

Worth knowing: Termites and soil properties can also limit trees in some savannas, so the list is arguable, but UPSC's key counts only fire, grazing herbivores and seasonal rainfall.

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

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Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper I, Series A. The paper on upsc.gov.in.