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Prentice Hall Biology, Chapter 16 Evolution of Populations. 16-1 Genes and Variation 16-2 Evolution as Genetic Change 16-3 The Process of Speciation

gene pool

the combined genetic information of all the members of a particular population

relative frequencies

the number of times a certain allele occurs in a gene pool compared with the number of times the other alleles occur

single-gene trait

trait controlled by a single gene

polygenic trait

trait controlled by two or more genes

directional selection

individuals at one end of the curve have higher fitness than individuals in the middle or at the other end

stabilizing selection

individuals near the center of the curve have higher fitness than individuals at the end

disruptive selection

individuals at the upper and lower end of the curve have higher fitness than individuals near the middle

genetic drift

random changes in allele frequencies in small populations

founder effect

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

Hardy-Weinberg principle

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

genetic equilibrium

the situation in which allele frequencies remain constant

5 conditions required to maintain genetic equilibrium

random mating, large population, no movement in/out of population, no mutations, no natural selection


species in a genetically isolated organism capable of reproducing

reproductive isolation

the members of two populations cannot interbreed and produce fertile offspring

behavioral isolation

two population are capable of interbreeding but have differences in courtship rituals or other types of behavior

geographical isolation

two populations are separated by geographic barriers such as rivers, mountains, or bodies of water

temporal isolation

two or more species reproduce at different times

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