unit 7a Flashcards
microevolution
change in allele frequencies in a population over generations. evolution at its smallest scale
3 mechanisms that cause allele frequency change
natural selection (adaptation to environment), genetic drift (chance events alter allele frequencies), gene flow (transfer of alleles between populations)
natural selection
adaptation to environment
genetic drift
chance events cause allele frequencies to fluctuate unpredictably from one generation to the next
gene flow
transfer of alleles between populations
genetic variation
differences in genes/other dna sequences among individuals
neutral variation
variation w no selective advantage/disadvantage. occurs within genes due to redundancy in genetic code
conditions for hardy-weinberg equilibrium
no mutations, random mating, no natural selection, large population size, no gene flow
founder effect
occurs when a few individuals become isolated from larger population. allele frequencies in smaller founder population differ from parent population
bottleneck effect
occurs when there’s drastic reduction in population size due to sudden change in environment. resulting gene pool may differ from original. if population remains small, it may be be further affected by genetic drift
relative fitness
contribution an individual makes to gene pool of next generation relative to contributions of other individuals
directional selection
favors individuals at one extreme end of the phenotypic range
disruptive selection
favors individuals at both extremes of the phenotypic range
stabilizing selection
favors intermediate variants and acts against extreme phenotypes
sexual dimorphism
difference in secondary sexual characteristics between sexes
intrasexual selection
direct competition among individuals of one sex for mates of opposite sex
intersexual selection
occurs when individuals of one sex are choosy in selecting mates
frequency-dependent selection
fitness of phenotype depends on how common it is
