UPSC Prelims 2014 · GS Paper I
Question 22: Environment and Ecology
Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of
AnswerUPSC’s answer is (b).
A lichen is a symbiotic association between a fungus and a photosynthetic partner, which is usually an alga (sometimes a cyanobacterium). The alga makes food by photosynthesis, while the fungus gives shelter, holds water and takes up minerals. Because lichens can grow on bare rock and slowly break it down into soil, they are pioneer species that start primary ecological succession. Remember: lichen = alga + fungus.
Why each option is right or wrong
- (a) Wrong. Lichens need a fungus; bacteria alone do not form the association.
- (b) Right. Lichens are a symbiosis of algae and fungi.
- (c) Wrong. Bacteria and fungi do not make a lichen, which needs a photosynthetic partner.
- (d) Wrong. Mosses are not a partner in a lichen.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2014, General Studies Paper I, Series A. The paper on upsc.gov.in.