Evolution describes the process by which species come to possess genetic adaptations to their environment. Its mechanism is natural selection . Natural selection acts through individuals by determining which individuals have the best adaptations to guarantee reproductive success. Because the state of environment is always changing temporally, natural selection is always influencing the genetic characteristics of the population over time. Thus, natural selection acts to adapt the population to its ever changing surrounds.
Evolutionary change is also a change in gene frequency .
The pattern of genetic variation changes from one generation to the next as natural selection determines which individuals are fittest. New genes enter the species gene pool way of mutations . By selecting thos organisms that will become reproductively successful, natural selection controls the future frequency of a population's genes. The appearance of new mutations in a population together with the change in gene frequency results in evolution. The spatial isolation of sub-populations from a main population is also an important condition for evolution.