What key concept relates to the change in genetic composition of a population over time?

The concept that relates to the change in genetic composition of a population over time is evolution. Evolution is a fundamental process that describes how species change across generations through mechanisms such as natural selection, genetic drift, mutation, and gene flow. These processes lead to changes in the allele frequencies within a population, ultimately resulting in the adaptation of organisms to their environments, the emergence of new species, or the extinction of existing species.

While adaptation, selection pressure, and variation are all important concepts in the study of evolution, they specifically pertain to different aspects of the evolutionary process. Adaptation refers to the traits that enhance an organism's ability to survive and reproduce in its environment, often as a result of evolutionary change. Selection pressure is the environmental factors that influence which individuals are more likely to survive and reproduce, thereby affecting evolution. Variation is the genetic diversity within a population, which is essential for evolution to occur, as it provides the raw material upon which natural selection can act.

In summary, evolution encompasses the broader concept of genetic change over time, integrating the effects of adaptations, selection pressures, and variations.