What is the term for the process by which characteristics of a population change over time?

The term that defines the process by which characteristics of a population change over time is actually evolution, which is influenced by various mechanisms, including natural selection, genetic drift, and gene flow. The mechanism you mentioned as the answer, selective pressure, refers to environmental factors that influence which individuals in a population survive and reproduce. This is an important concept, as selective pressure can drive natural selection by favoring certain traits that confer advantages to individuals in specific environments.

Natural selection is the process where organisms that are better adapted to their environment tend to survive and produce more offspring. Gene flow is the transfer of genetic material between separate populations, which can introduce new genetic variations. Genetic drift is the evolution of a population’s traits due to chance events, particularly in small populations, leading to random changes in allele frequencies.

While selective pressure is a significant factor affecting evolution, it is more an influence on the mechanism rather than the overarching process. The correct understanding and terminology about how populations change over time encompasses several interconnected processes that all contribute to the overall concept of evolution.