bio ch23 key terms

Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes

Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. typically, the surviving population is no longer genetically representative of the original population.

The aggregate of all of the alleles for all of the loci in all individuals in a population. the term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population.

The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.

Differences between the gene pools of geographically separate populations or population subgroups.

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population

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

A direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.

(het'-er-o-zi-go'-si-te) The percent, on average, of a population's loci that are heterozygous in members of the population.

An aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated.

Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.

The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

(di-mor'-fizm) Marked differneces between the secondary sex characteristics of males and females.

Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.

Natural selection that maintains two or more phenotypic forms in a population.

Evolutionary change below the species level; change in the allele frequencies in a population over generations.

The condition describing a nonevolving population (one that is in genetic equilibrium)

A localized group of individuals of the same species that can interbreed, produced fertile offspring.

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.

A graded change in a character along a geographic axis.

A decline in the reproductive success of individuals that have a phenotype that has become too common in a population.

Genetic variation that does not appear to provide a selective advantage or disadvantage.

The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.

(myu-ta'-shun) A change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.

Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.