Chapter 16 &17 Vocab

Evolution

Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.

Fossil

A trace of an ancient organism that has been preserved in rock.

artificial selection

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

Adaptation

A trait that helps an organism survive and reproduce

Fitness

Ability of an organism to survive and reproduce in its environment

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.

Biogeography

Study of past and present distribution of organisms

homologous structures

Structures in different species that are similar because of common ancestry.

analogous structures

Body parts that share a common function, but not structure

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.

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

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

single-gene trait

trait controlled by one gene that has two alleles

polygenic traits

traits controlled by two or more genes

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

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

genetic drift

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

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

genetic equilibrium

situation in which allele frequencies remain constant

Hardy-Weinberg Principle

principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

gene flow

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

Species

A group of similar organisms that can breed and produce fertile offspring.

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

Speciation

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

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

form 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