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Localized group of individuals that are capable of interbreeding and producing fertile offspring
population
All of the genes in a population at any one time
gene pool
Modern synthesis was born from
Darwinian evolution + Mendelian genetics
Existence of two or more distinct morphs each represented in a population in high enough frequencies to be readily noticeable
Polymorphism (phenotypic)
Calculate the frequency of alleles
red allele frequency= all red alleles/total#allele
Hardy-Weinberg Theorem
Frequencies of alleles in population gene pool should remain constant across generations
p2+2pq+q2=1
Change in DNA nucleotide sequence; corresponding change in mRNA may alter protein synthesis
mutation
Random fluctuation in gene pool (especially important in small populations)
Genetic drift
Sudden event dramatically reduces population size. Sudden event dramatically reduces population size, future variations
Bottleneck effect- ie: a hurricane devastates a population only leaving certain survivors
Isolated group starts new population with no further gene glow from source population. Some populations are not able to interact with the rest of the group
Founder effect
Consequence of the bottleneck & founder effects: artificial selection
inbreeding
Genetic input from other populations
gene flow
Mean proportion of loci that are heterozygous; used to help measure genetic diversity for the population
average heterozygosity
#heterozygote individ/total population
Gene pool differences among populations
geographic variation
graded variation in a trait parallels environmental gradient
cline
wild plants from different altitudes were grown in controlled conditions
common garden experiment
three ways natural selection can alter variation in a population
directional, disruptive, stabilizing selection
favors intermediate variants by acting against both extremes
stabilizing selection
favors individuals on both extremes of phenotypic range
disruptive selection
natural selection that favors individuals at one end of the phenotypic range
directional selection
natural selection for mating success; may produce
sexual selection
distinct male vs female adult phenotypes (secondary sex characteristics)
sexual dimorphism
direct competition for potential mates. Mate choice; one sex usually females are choosy in selecting their mates
intersexual selection
Maintains stable frequencies of multiple phenotypic forms
balancing selection
success of one phenoypic morph declines when it becomes too common in the population