UPSC Prelims 2021 · GS Paper I
Question 22: Environment and Ecology
Consider the following kinds of organisms :
- 1.Copepods
- 2.Cyanobacteria
- 3.Diatoms
- 4.Foraminifera
Which of the above are primary producers in the food chains of oceans?
AnswerUPSC’s answer is (b).
Primary producers make their own food from sunlight or chemicals. In oceans these are mainly the phytoplankton: diatoms and cyanobacteria both photosynthesise and form the base of marine food chains. Copepods are tiny crustaceans that graze on phytoplankton, so they are consumers. Foraminifera are single-celled organisms that feed on other organisms, so they are also not producers. Remember: phytoplankton are producers; zooplankton are consumers.
- 1. Copepods graze on phytoplankton, so they are consumers.
- 2. Cyanobacteria photosynthesise and are primary producers.
- 3. Diatoms are photosynthetic phytoplankton at the base of marine food chains.
- 4. Foraminifera are single-celled organisms that feed on other organisms.
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: Copepods graze on phytoplankton, so they are consumers.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Cyanobacteria photosynthesise and are primary producers.
Only (b) is left. You didn’t need statements 3 or 4.
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: copepods are consumers.
- (b) Right: cyanobacteria and diatoms photosynthesise and are primary producers.
- (c) Wrong: foraminifera are not producers.
- (d) Wrong: neither copepods nor foraminifera make their own food.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper I, Series A. The paper on upsc.gov.in.