Question

Which unit of organisms evolves—an individual, a population, or a species? Explain.

Answer 1

Population. Individuals in a population will interbreed with mutations, and in time the mutations will reproduce to evolve.
The only way species can be the answer is if the whole species is in a population, otherwise a whole species of animals wouldn't evolve together.

Answer 2

A Population

Step-by-step explanation:

Population is a group of individuals of same species that are present together in a habitat. Presence of variations in individuals serve as raw material for evolution. Natural selection favors the individuals with beneficial variations. It gradually leads to evolution of better adapted population consisting of individuals carrying the beneficial variations. Hence, a population evolves with time.