evolution of populations Flashcards
what is a gene composed of?
a combination of two alleles
how many alleles are there per chromosome?
one
evolution is the change in…
the frequency of alleles in a population between generations
what are the four factors that can result in evolutionary change?
- natural selection
- mutation
- genetic drift
- gene flow
what is fitness?
the extent to which an individuals genotype is represented in the next generation
natural selection can affect that distribution of allele frequencies in three types of selection; what are they?
direction, disruptive, and stabilizing selection
what occurs in directional selection? (3)
-the extreme phenotype with the highest fitness is favored
-can increase or decrease the trait
-shift in the mean of the population, where variance/spread stays the same
what occurs in disruptive selection? what does it result in? what does it maintain?
-two opposite end extremes are favored
-results in polymorphism
-maintains variation since there are two means
what is stabilizing selection? what is decreasing? what remains constant?
-common phenotypes are favored, extremes are selected against
-variance decreases, mean of the population stays the same
in what forms of selection are extremes favored?
disruptive and directional
in what type of selection does variance decrease?
stabilizing
which mechanisms do not result in adaptation in the factors that result in evolutionary change
mutation, gene flow and genetic drift
what are mutations?
a change in an individuals DNA that is random and can be good, bad or neutral in a current situation
what is gene flow?
transfer of genes (alleles) between populations like migration
in gene flow, what happens to variation within a population? what happens to variation between populations?
increased variation within, decreased variation between
