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.
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3 ✓ UPSC's answer
Why the answer is (d)
• Cnidarians: reef-building corals and some sea anemones host photosynthetic zooxanthellae algae in their tissues; anemones also partner with clownfish (item 1).
• Fungi: lichens (fungus + alga/cyanobacterium) and mycorrhizae (fungus + plant roots) are textbook symbioses (item 2).
• Protozoa: flagellates in termite guts digest cellulose for the host, and some protozoa host algae — mutualistic symbiosis (item 3).
• Symbiosis spans mutualism, commensalism and parasitism, and all three groups have species in such relationships.
• Hence 1, 2 and 3, option (d).
Why the other options are wrong
- (a) 1 and 2 only
- Protozoa (e.g. termite-gut flagellates) also form symbioses.
- (b) 2 and 3 only
- Cnidarians (corals with zooxanthellae) also form symbioses.
- (c) 1 and 3 only
- Fungi (lichens, mycorrhizae) are classic symbionts too.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.