microevolution - exam 4 Flashcards
microevolution
generation to generation change in allele frequencies in a population
gene pool
sum of all of the alleles in a population
natural selection acts on phenotypes or genotypes
pheotypes
evolutionary change requires change in phenotypes or genotpyes
genotypes
genetic drift
chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next
where is genetic drift particularly relevant
small populations
can greatly reduce or even eliminate alleles
founder effect
individuals isolated from main population
in “new” or “founded” population – loss of alleles & increase of alleles that were rare in og population
fixed allele
allele that is the only variant that exists for that gene in the population
bottleneck effect
population goes through a period in which its size decreases
lots of alleles lost, low genetic diversity
gene flow
genetic exchange due to the migration of fertile individuals or gametes between populations
reduces differences BETWEEN pops
increases diversity WITHIN pops
can increase or decrease fitness of a population
mutation
heritable change in DNA
random
rare
mostly neutral
natural selection
accumulates & maintains favorable genotypes in a population
must have genetic variation
directional selection
favors individuals at one extreme of a phenotypic distribution
stabilizing selection
favors individuals w/ intermediate phenotypes
being average is best
disruptive selection
favors individuals with extreme phenotypes
average is the worst
sometimes leads to speciation
