Biology Unit 3 Review

Evolution

The process by which modern organisms have descended from ancient organisms.

Natural Selection

A natural process resulting in the evolution of organisms best adapted to the environment; survival of the fittest.

Variation

The differences among traits within a single species.

Specie

A group of organisms that are closely related and can mate to produce fertile offspring.

Speciation

The formation of new species as a result of evolution.

Common Ancestry

Organisms that have a close genetic relationship with the same extinct species.

Root specie

Specie from which all others shown branched from.

Homologous Structures

Structures that are similar in different species of common ancestry.

Analogous Structures

Body parts that share a common function, but not structure.

Vestigial Structures

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

Fitness

How well an organism can survive and reproduce in its environment.

Adaptation

An inherited behavior or physical characteristic that helps an organism survive and reproduce in its environment.

Divergent Evolution

Evolution of one or more closely related species into different species; resulting from adaptations to different environmental conditions.

Convergent Evolution

Evolution toward similar characteristics in unrelated species.

Coevolution

Process in which two or more species evolve in response to changes in each other.

Punctuated Equilibrium

Patterns of evolution in which long stable periods are interrupted by brief periods of more rapid change.

Allele Frequency

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene.

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

Directional Selection

Form of natural selection in which the entire 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.

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.

Reproductive Isolation

Separation of species of populations due to geographical, behavioral, physiological, or genetic barriers so that they cannot breed successfully.

Behavioral Isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding.

Geographic Isolation

For of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water.

Temporal Isolation

Form of reproductive isolation in which two populations reproduce at different times.

Gene Flow

Movement of alleles into or out of population due to the migration of individuals to or from the population.

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.