phenotypic variation
differences of observable traits from organisms in a species
genotypic variation
differences in the DNA sequence among individuals of a species
sources of genetic variation
mutations and recombinations
mutation
generates new variations in DNA sequences
recombinations
shuffle existing variations to make new combinations
somatic mutation
affects only the cells descended from the cell in which the mutation originally arose, affects individuals not passed to offspring
germ-line mutations
occur in productive cells, passed on to the next generations
point mutation
one base pair is replaced by a different base pair
duplication mutation
segment of DNA is repeated
deletion
segment of DNA removed
transposable elements
DNA sequence that can jump from one place to another
allele frequency
the number of allele x present in the population divided by the total number of alleles of that gene; patterns of genetic variation
genotype frequency
proportion of each genotype at a particular gene or set of genes
genetic drift
random change in allele frequencies from generation to generation
bottleneck
when a large population is reduced to just a few individuals
founder effect
occurs when a few individuals from a larger population establish a new population
migrations
movement of individuals from one population to another
gene flow
the movement of alleles from one population to another
mutation
source of genetic variation and a mechanism of evolution
nonrandom mating
individuals preferentially choose mates according to their genotypes
hardy Weinberg equilibrium
occurs when the genetic makeup of a population does not change over time
null hypothesis
a hypothesis that states that nothing is occurring