Darwin and theory of Evolution

directional selection

Form of natural selection in which the entire bell curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

disruptive selection

form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

Adaptation

A trait that helps an organism survive and reproduce

negative selective pressure

Have a lower survival rate and traits are not desired;Selected against

positive selective pressure

an environmental factor that selects for a particular trait, eventually leading to an abundance of that trait in a population

evolutionary fitness

a measurement of the degree to which an organism can successfully adapt to its environment AND can reproduce fertile offspring

survival of the fittest

Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection

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.

vestigial structures

A structure that is present in an organism but no longer serves its original purpose

homologous structures

similar structures that related species have inherited from a common ancestor; are often adapted to different environments, serving different functions

analogous structures

structures that do not have a common evolutionary origin but are similar in function

Variation

Any difference between individuals of the same species.

artificial selection

Breeding organisms with specific traits in order to produce offspring with identical traits.

antibiotic resistance

Resistance evolving rapidly in many species of prokaryotes due to overuse of antibiotics, especially in agriculture.

Macroevolution

large-scale evolutionary changes that take place over long periods of time

Biogeography

Study of past and present distribution of organisms