UPSC Prelims 2011 · GS Paper I
Question 48: Environment and Ecology
Consider the following :
- 1.Photosynthesis
- 2.Respiration
- 3.Decay of organic matter
- 4.Volcanic action
Which of the above add carbon dioxide to the carbon cycle on Earth ?
AnswerThe answer is (c).
Photosynthesis removes carbon dioxide from air and water, so it takes carbon out of the atmosphere rather than adding to it. Respiration by plants and animals, and decay of organic matter by microbes, both release carbon dioxide, and volcanic eruptions release carbon dioxide from the Earth's interior. So respiration, decay and volcanic action add carbon dioxide to the carbon cycle, and photosynthesis does not.
- 1. Photosynthesis absorbs carbon dioxide.
- 2. Respiration releases carbon dioxide.
- 3. Microbial decay releases carbon dioxide.
- 4. Volcanoes release carbon dioxide.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (d) go: each of them includes 1.
What you needed to know: Photosynthesis absorbs carbon dioxide.
- Then, if you were sure statement 4 is correct, (b) goes: it leaves 4 out.
What you needed to know: Volcanoes release carbon dioxide.
Only (c) is left. You didn’t need statements 2 or 3.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
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) Photosynthesis takes up carbon dioxide, and this omits respiration and decay.
- (b) Omits volcanic action, which also adds carbon dioxide.
- (c) Right: respiration, decay and volcanic action add carbon dioxide.
- (d) Photosynthesis removes carbon dioxide, so it cannot be included.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.