What is the process called that describes the change in populations of organisms over time?

The process that describes the change in populations of organisms over time is known as evolution. Evolution refers to the gradual changes in the heritable traits of biological populations over successive generations. It is driven by mechanisms such as natural selection, mutation, gene flow, and genetic drift. Over time, these processes can lead to the emergence of new species, changes in existing species, and the overall diversity of life on Earth.

While adaptation is part of the evolutionary process, as it involves the changes in traits that enhance survival and reproductive success, it is not the overarching term for the change of populations over time. Selective pressure, which refers to external factors that influence an organism's chances of survival, is a factor that drives evolution but does not encompass the full concept of evolutionary change itself. Punctuated equilibrium describes a specific model of evolution describing periods of rapid change interspersed with periods of stability but does not define the broader concept of evolutionary change in populations. Thus, evolution is the most comprehensive term to describe the ongoing process of change within populations over time.