UPSC Prelims 2013 · GS Paper I
Question 53: Environment and Ecology
With reference to the food chains in ecosystems, which of the following kinds of organism is/are known as decomposer organism/organisms?
- 1.Virus
- 2.Fungi
- 3.Bacteria
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (b).
Decomposers break down dead organic matter into simpler substances and return nutrients to the soil. Fungi and bacteria secrete enzymes that digest dead plants and animals, so they are the decomposers in a food chain. Viruses are not decomposers: they cannot multiply outside the living cells of a host and do not feed on dead matter.
- 1. Viruses multiply only inside living host cells.
- 2. Fungi digest dead organic matter.
- 3. Bacteria decompose dead organic matter.
How you could have got this
- If you were sure statement 1 is not correct, (a), (c) and (d) go: each of them includes 1.
What you needed to know: Viruses multiply only inside living host cells.
Only (b) is left. You didn’t need statements 2 or 3.
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. Viruses do not decompose dead matter.
- (b) Correct. Fungi and bacteria are decomposers.
- (c) Wrong. Viruses are not decomposers, and fungi are left out.
- (d) Wrong. Viruses cannot be counted as decomposers.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.