Hon Bio Unit 12: Just a Theory - Natural Selection

Evolution

The gradual change in a species over time

Adaptation

inherited characteristic that increases an organism's chance of survival

Variation

Any difference between individuals of the same species

Mutation

A change in a gene or chromosome

Overproduction/Competition

organisms produce more offspring than can survive; organisms will have to survive in a habitat with limited resources

Speciation

the formation of new and distinct species in the course of evolution

Extinction

typically describes a species that no longer has any known living individuals

Reproductive Advantage

organisms with certain variations survive better and have more organisms than those without the variation

post-zygotic isolation

mating occurs, but offspring are sterile or inviable

pre-zygotic isolation

mating and fertilization are prevented

disruptive selection

favors individuals at both extremes of the phenotypic range

stabilizing selection

occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

directional selection

occurs when natural selection favors one of the extreme variations of a trait