p. 33 – Mechanisms of Evolution

Mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals The environment is the selecting agent (determines which traits are beneficial) Happens in nature without human interference Natural Selection

Adaptation Feature that allows an organism to better survive Long neck on giraffe Camouflage of a tiger Adaptation

Process by which humans change a species by breeding it for certain traits Artificial Selection

Measure of the ability to survive and produce more offspring compared to other members of the population Fitness

Convergent Evolution – evolution toward similar characteristics in unrelated species Wings on birds and wings on insects Tail fin on fish, shark and dolphins Produces analogous structures 2 types of Evolution

Divergent Evolution – when closely related species evolve in different directions Kit fox and red fox Bones in arms performing different functions for different animals Produces homologous structures 2 Types of Evolution

Directional selection One extreme phenotype is favored by natural selection Directional selection

Both extreme phenotypes are favored by natural selection Disruptive Selection

Stabilizing Selection The intermediate or “average” phenotypes are favored by natural selection over the extreme phenotypes Stabilizing Selection