Biology Chapter 17 Vocabulary

Chapter 17 Evolution of Populations Vocabulary

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

The number of times that an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene

Single-gene trait

a trait controlled by one gene that has two alleles

polygenic trait

a trait controlled by two or more genes

Directional selection

a form of natural selection in which 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

a form of natural selection in which individuals near the center of a distribution curve have higher fitness than individuals at either end of the curve

Disruptive selection

a form of natural selection in which individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle of the curve

Genetic drift

a random change in allele frequencies caused by a series of chance occurrences that cause an allele to become more or less common

bottleneck effect

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

founder effect

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

genetic equilibrium

a situation in which the allele frequencies in a population remain the same

Hardy-Weinberg principle

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

sexual selection

the process by which individuals select mates on the basis of heritable traits

species

a population whose members can breed and produce fertile offspring

speciation

the formation of a new species

Reproductive isolation

the separation of a species or population so that members can no longer interbreed

Geographic isolation

a form of reproductive isolation in which members are separated by geographic barriers such as rivers, mountains, or bodies of water

behavioral isolation

a form of reproductive isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding

Temporal Isolation

a form of reproductive isolation in which 2 or more species reproduce at different times

Molecular clock

a method that uses mutation rates in DNA to estimate the length of time that two species have been evolving independently