2013 GS Paper I, all questions

UPSC Prelims 2013 · GS Paper I

Question 23: Environment and Ecology

Which one of the following is the correct sequence of ecosystems in the order of decreasing productivity?

aOceans, lakes, grasslands, mangroves
bMangroves, oceans, grasslands, lakes
cMangroves, grasslands, lakes, oceans
dOceans, mangroves, lakes, grasslands

AnswerUPSC’s answer is (c).

Productivity is highest where water, nutrients and warmth are plentiful and fully used, such as mangroves and estuaries. Grasslands come next, then lakes, and open oceans are lowest because nutrients are scarce and light reaches only the top layer of water. The sequence mangroves, grasslands, lakes, oceans is therefore in decreasing order of productivity.

Why each option is right or wrong
  • (a) Wrong. Oceans are the least productive, not the most.
  • (b) Wrong. Oceans are below grasslands and lakes in productivity.
  • (c) Correct. Mangroves, then grasslands, lakes and oceans.
  • (d) Wrong. Oceans do not top the list, and grasslands exceed lakes.

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

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Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.