Which evolutionary process involves the adaptation of organisms to their environment over time?

Natural selection is the evolutionary process that involves the adaptation of organisms to their environment over time. It is based on the principle that individuals with advantageous traits are more likely to survive and reproduce, passing those traits on to the next generation. This leads to a gradual change in the population, enhancing the traits that improve fitness in a particular environment. For example, in a population of birds, those with beaks that are better suited for the available food sources will tend to survive longer and produce more offspring, thereby increasing the frequency of that beak trait in the population over generations.

The other processes listed contribute to genetic variation and population changes but do not directly drive the adaptation of organisms to their environment. Gene flow refers to the transfer of genetic material between populations, which can introduce new traits but is not inherently about adaptation. Mutations create new genetic variation but do not necessarily lead to adaptation unless those mutations confer some advantage. Genetic drift leads to changes in trait frequencies due to chance events, particularly in small populations, and can sometimes result in traits that are not advantageous becoming prevalent.