Evolution is the process of adaptation through mutation which allows more desirable characteristics to be passed to the next generation. For living organisms to adapt and change to environmental pressures, genetic variation must be present.

With genetic variation, individuals have differences in form and function that allow some to survive certain conditions better than others. Evolution may be convergent with similar traits evolving in multiple species or divergent with diverse traits evolving in multiple species that came from a common ancestor.

species — group of populations that interbreed and produce fertile offspring. vestigial structure — physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor. adaptation — heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment. variation — genetic differences among individuals in a population.