Selection.

Selection, also known as natural selection, is one of the most important factors in evolution, or the process by which the traits of living things change over time. Developed by English naturalist Charles Darwin, the theory of evolutionary selection states that every generation of living things has some degree of variation. These variable factors can make it easier or harder for individuals to survive. Individuals with variations that help them survive will be more likely to reproduce and genetically pass along those special variations to the next generation. The other individuals, with less beneficial variations, will be less likely to reproduce and pass along their traits. Through this process, the most beneficial variations eventually spread widely through the entire population, while less desirable variations slowly disappear. The result of these changes is the evolution of species that has been fundamental to the development of all living things.