UPSC Prelims 2021 · GS Paper I
Question 30: Environment and Ecology
Which of the following have species that can establish symbiotic relationship with other organisms?
- 1.Cnidarians
- 2.Fungi
- 3.Protozoa
Select the correct answer using the code given below.
AnswerUPSC’s answer is (d).
Symbiosis is a close, long-term association between different species. Cnidarians such as corals live with symbiotic algae (zooxanthellae). Fungi form lichens with algae or cyanobacteria and mycorrhizae with plant roots. Protozoa live inside termites' guts and help digest wood. So each group has species that form symbiotic relationships. Remember: coral-algae, lichens, mycorrhiza and termite-protozoa are the standard examples.
- 1. Corals and some other cnidarians host symbiotic algae.
- 2. Fungi form lichens and mycorrhizae.
- 3. Gut protozoa in termites help them digest wood.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Corals and some other cnidarians host symbiotic algae.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Fungi form lichens and mycorrhizae.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Gut protozoa in termites help them digest wood.
Only (d) is left. This one needs every statement.
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: protozoa also have symbiotic species.
- (b) Wrong: cnidarians (corals) also have symbiotic species.
- (c) Wrong: fungi also have symbiotic species.
- (d) Right: cnidarians, fungi and protozoa all include symbiotic species.
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.