Biology

homologous structures

Homologous structures are similar structures that serve different functions, such as a human's arm, a dog's leg, a bird's wing, and a whale's fin, which look similar but serve different purposes. Homologous structures point to a common ancestor and support evolution.

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Adaptation

A trait that helps an organism survive and reproduce

Catastrophism

A principle that states that geologic change occurs suddenly

Evolution

Change over time

Charles Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

Cambian Explosion

The rapid diversification of multicellular animal life around the beginning of the Cambrian Period, resulting in the appearance of almost all modern animal phyla.

Gradualism

The theory that evolution occurs slowly but steadily

Fitness

ability to survive and reproduce

vestigial structures

remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.

analogous structures

similarities among unrelated species that result from convergent evolution