Question

In commensalism
A. Population of commensal and host remains unaffected.
B. Population of commensal increases, while that of the host remains unaffected.
C. Population of both commensal and host increases.
D. Population of commensal increases while the population of hosts gradually decreases.

Answer 1

The species interact in nature and establish various population interactions or population relationships. This is because no species is independent and can survive on its own. These interactions are either beneficial, detrimental, or neutral.

Complete answer:
Commensalism is a type of population interaction in which one species is benefitted and another species is neither benefited nor harmed, i.e., it remains neutral. The species which is benefitted from the relationship or interaction is known as the commensal, and the species which stays neutral in the relationship is the host. Due to this reason in commensalism relationship, the population of commensal increases while the population of the host remains unaffected. Some popular examples of commensalism as seen in nature are –
Orchids growing on plants like mango get benefits in the form of shelter.
Small fishes like barnacles growing on the back of the Whale fish get benefits in the form of shelter.
Clownfishes living amongst Sea anemones get benefits in the form of protection from predators.
Thus, based on the above information we can conclude that in commensalism population of commensal increases, while that of the host remains unaffected.

Hence, the correct answer is an option (B).

Note: Commensalism should not be confused with amensalism. In amensalism, one species is harmed from the relationship whereas the other species are neutral. The species which is harmed is known as the amensal whereas, the other species which is neutral is the host. In amensalism, the growth of one species is inhibited by the growth of another species by secreting certain types of chemicals.