Chapter+16+Vocab

section 1 population genetics - the study of evolution from a genetic point of view

bell curve - graph which shows that though some of a population have extreme traits, most are average; shaped like a bell

gradualism- the idea that species originate through a gradual change of adaption

gene pool- all the genes for all of the traits in a population

Allele frequency- the percentage of an allele in a gene pool

phenotype frequency - a ratio stating the number of times a specific phenotype occurs in a population in a single generation

Hardy-Weinberg genetic equilibrium -the stability of gene frequencies across generations

section 2 Immigration - the movement of individuals into a population

Emigration - the movement of individuals out of a population

gene flow - the movement of genes into or out of a population

genetic drift - a shift in allele frequencies in a population due to chance

assortative mating - the selection of a mate based on similarity of characteristics

directional selection - when one of the extremes become more beneficial and the bell curve shifts to one side

disruptive selection - when both extremes become more beneficial and a dip is created in the bell curve

sexual selection - the production of offspring from the combination of genetic material from two parent organisms

section 3 speciation - the formation of a new species

morphology - the study of the internal and external structure and form of an organism

biological species concept - the principle that defines an a species as those organisms can produce offspring together

geographic isolation - the physical separation of populations

reproductive isolation - the inability of formerly interbreeding organisms to produce offspring

prezygotic isolation - a barrier to successful breeding that occurs before fertilization, such as differences in mating time or behavior

postzygotic isolation - a barrier to successful breeding that occurs after fertilization, such as the production of nonviable or sterile offspring

punctuated equilibrium -this idea argues that speciation occurs quickly in rapid bursts, with a long periods of genetic equilibrium in between