$A$ cuckoo laying eggs in the nest of other species of birds is an example of

Give scientific reasons: The members of a population do not breed with other populations.

How do parasites harm the host?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $(A)$: Recent studies do not entirely support the Gause's 'Competitive Exclusion Principle' in nature.
Reason $(R)$: Recent studies of competition rule out the occurrence of interspecific competition in nature.
In the light of the above statements,choose the most appropriate answer from the options given below:

Explain commensalism with the example of an egret and cattle.

Choose the incorrect sentence.