Two species evolve in such a close relationship with each other that the evolution of one species affects the evolution of the other species. This is called

a. adaptive radiation

b. coevolution

c. convergent evolution

d. gradualism

Coevolution.

Explanation:

Coevolution may be defined as the process of evolution of two species together. The coevolution was first coined by Peter H. Raven and Paul R. Ehrlich.

The co evolution effects the evolution of the species and reciprocally effect each other. For example: the insect and the flowering plant both evolve with each other and may sometime develop the mutual relationship each other.

Thus, the correct answer is option (b).