Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of
- (a) algae and bacteria
- (b) algae and fungi ✓ UPSC's answer
- (c) bacteria and fungi
- (d) fungi and mosses
Why the answer is (b)
• A lichen is a mutualistic partnership between a fungus (which provides structure, water and minerals) and a photosynthetic partner — an alga or cyanobacterium — that supplies food — option (b).
• As pioneers of primary succession, lichens secrete acids that weather bare rock into soil.
• Bacteria with algae (a) or fungi (c), and fungi with mosses (d), do not form lichens.
• Hence option (b).
Why the other options are wrong
- (a) algae and bacteria
- Lichens involve fungi, not bacteria alone with algae.
- (c) bacteria and fungi
- Bacteria–fungi is not a lichen.
- (d) fungi and mosses
- Mosses are not lichen partners.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2014, held on 24 August 2014. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.