Question

Which of the following organisms cite an example of commensalism?

• A. Sea anemone and clown fish
• B. Sea anemone and hermit crab
• C. Balanus and Chthamalus
• D. None of the options

Answer 1

The Correct Option is A

The relationship between sea anemone (a coelenterate) and clown fish is symbiosis (mutualism) i.e., both the organisms are benefited from the relationship. A sea anemone makes an ideal home for a clown fish. Its poisonous tentacles provide protection from predators and the clown fish makes its meals from the anemone?s left overs. The clown fish in turn helps the anemone to catch its prey by luring other fish towards it. By eating the leftover food and any dead tentacle, clown fish helps in keeping the anemone and the area around it clean.
The relationship between sea anemone and hermit crabs is an example of symbiosis (mutualism). In their relationship, both the organisms i.e., sea anemone and the hermit crab are benefited. The hermit crab resides in an empty gastropodan shell for protection. The sea anemone also attaches itself to the shell. The anemone is carried by the crab to fresh feeding sites increasing the availability of food for it. The crab in turn is protected from the predators by the tentacles of the sea anemone. The association between sea anemone and hermit crab had earlier been considered as an example of commensalism or proto-cooperation by some workers, but it better fits into the category of mutualism as the two organisms are always found together, never alone.
Lichens also represent the most familiar example of symbiosis in which the algal partner (phycobiont) and the fungal partner (mycobiont) live together and mutually benefit each other. The fungus obtains food prepared by the alga and the alga obtains water and mineral salts absorbed by the fungus from the soil.
The interaction between Balanus and Chthamalus is an example of competition. In habitats where Balanus and Chthamalus coexist, the realised niche of Chthamalus is smaller than its fundamental niche because of competition from Balanus. Chthamalus occupies only shallow water and Balanus occupies only deep water on a rocky coast. In the absence of Balanus, Chthamalus occupies both shallow water and deep water.