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.

Correct Option (D) All three groups-Cnidarians, Fungi, and Protozoa-include species capable of establishing symbiotic relationships with other organisms. - Cnidarians: Many coral species, which are cnidarians, form a mutualistic relationship with zooxanthellae (symbiotic algae). The algae perform photosynthesis, providing nutrients to the coral, while the coral offers protection and a stable environment. - Fungi: Fungi are well-known for their symbiotic associations. Lichens are a classic example, representing a mutualistic relationship between fungi and algae or cyanobacteria. Mycorrhizae involve a symbiotic association between fungi and the roots of most plant species, facilitating nutrient uptake for the plant and receiving carbohydrates from the plant. - Protozoa: Certain protozoans, such as flagellates found in the guts of termites, establish mutualistic relationships. These protozoans possess enzymes that enable them to digest cellulose, providing essential nutrients to the termite host, while receiving shelter and a constant food supply in return. Incorrect Options - Option 1 is incorrect because Protozoa also form symbiotic relationships, as seen in termite guts. - Option 2 is incorrect because Cnidarians, particularly corals, are widely recognized for their symbiotic associations with algae. - Option 3 is incorrect because Fungi are central to numerous symbiotic relationships, including lichens and mycorrhizae.

IAS 2021 — Environment & Ecology Environment & Ecology

2021mcqmedium

Which of the following have species that can establish symbiotic relationship with other organisms?

Cnidarians
Fungi
Protozoa

Select the correct answer using the code given below.

Official previous-year question

Verified 2 Aug 2026.

Options

A1 and 2 only
B2 and 3 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

Correct Option (D)

All three groups-Cnidarians, Fungi, and Protozoa-include species capable of establishing symbiotic relationships with other organisms.

Cnidarians: Many coral species, which are cnidarians, form a mutualistic relationship with zooxanthellae (symbiotic algae). The algae perform photosynthesis, providing nutrients to the coral, while the coral offers protection and a stable environment.
Fungi: Fungi are well-known for their symbiotic associations. Lichens are a classic example, representing a mutualistic relationship between fungi and algae or cyanobacteria. Mycorrhizae involve a symbiotic association between fungi and the roots of most plant species, facilitating nutrient uptake for the plant and receiving carbohydrates from the plant.
Protozoa: Certain protozoans, such as flagellates found in the guts of termites, establish mutualistic relationships. These protozoans possess enzymes that enable them to digest cellulose, providing essential nutrients to the termite host, while receiving shelter and a constant food supply in return.

Incorrect Options

Option 1 is incorrect because Protozoa also form symbiotic relationships, as seen in termite guts.
Option 2 is incorrect because Cnidarians, particularly corals, are widely recognized for their symbiotic associations with algae.
Option 3 is incorrect because Fungi are central to numerous symbiotic relationships, including lichens and mycorrhizae.

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