What term describes the gradual change in species composition over time?

The correct term that describes the gradual change in species composition over time is succession. Succession refers to the process by which ecosystems change and develop over time, particularly after a disturbance, leading to a series of stages that eventually establish a stable climax community. This process can occur in various environments, including forests, grasslands, and aquatic systems, and involves the replacement of one community by another until a stable ecosystem is formed.

In contrast, adaptation refers specifically to the adjustments organisms make to survive and reproduce in their environment, often as a result of evolutionary pressures. Mutation is the alteration of the genetic material in an organism, which can lead to changes in traits but is not a process that describes changes in community structure over time. Evolution, while closely related to changes in species over time, encompasses broader changes including genetic variations and natural selection, rather than focusing specifically on the composition of communities in a particular area.