Evolution

Evolution is the process of change in a population of organisms over many generations. This process of genetic and phenotypic change has resulted in the modern diversity of life from a few ancient common ancestors.

Evolution is how organisms have adapted and changed in response to environmental pressures. The process involves four main forces:

• selection
• mutation
• genetic drift
• gene flow (migration)

For a species to evolve, genetic variation must be present. This variation is generated by mutation, and is distributed throughout a population by genetic drift and gene flow. Genetic variation causes individuals to have differences in form and function that allow some to survive certain conditions better than others. Natural selection is the term for how an environment "selects" the individuals with the greatest fitness. The result is that alleles that confer beneficial traits or behaviors are more likely to passed on to future generations in the population. Deleterious qualities are selected against. As environments change, the direction and strength of selection also changes.

Convergent evolution shows that similar traits can evolve in multiple species, while divergent evolution describes the development of diverse traits leading to multiple species from a common ancestor.

The theory of evolution is the unifying theory of biology. Evidence of evolution can be observed in all fields of biology and it is the framework within which biologists ask questions about the living world. Its power is that it provides direction for predictions about living things that are borne out in experiment after experiment.

All living species, from bacteria to baboons to blueberries, evolved at some point from a different species. Although it may seem that living things today stay much the same, that is not the case - evolution is an ongoing process.