Question

natural selection causes gradual changes in ______

a. an individual

b. a population

c. acquired traits

d. an environment

Explanation:

Natural selection acts on the heritable traits of organisms within a population over generations. An individual's traits don't change via natural selection (A is wrong). Acquired traits aren't heritable and thus not subject to natural selection (C is wrong). Natural selection is about organisms adapting to the environment, not changing the environment itself (D is wrong). Populations change as favorable traits become more common over time due to natural selection.

Answer:

B. a population