AP Bio - populations and gene flow

a group of individuals of the same species that live in the same area and interbreed to produce fertile offspring

population

a population’s genetic makeup

gene pool

if there is only one allele present for a particular locus in the population it is _______

fixed

many fixed alleles =

less genetic diversity

small scale genetic changes in a population

microevolution

changes in genetic code

• can form new alleles

• natural selection can act on varied phenotypes

• mutation rates tend to be slow in plants in animals and fast in prokaryotes due to a faster generation time

mutations

chance events that cause a change in allele frequency from one generation to the next

• most significant to small populations

• can lead to a loss of genetic variation

• can cause harmful alleles to become fixed

• does not produce adaptions

genetic drift

two types of genetic drift

bottleneck and founder effects

when a large population is drastically reduced by a non-selective disaster

• flood, famine, fires, hurricanes, hunting, etc

• some alleles may become overrepresented, underrepresented, or absent

bottleneck effect

when a few individuals become isolated and establish a new small population w/ a gene pool that differs from the larger population

• loss of genetic diversity

founder effect

the transfer of alleles into or out of a population due to fertile individuals or gametes

• ex: pollen being blown to a new location

alleles can also be transferred between populations

• ex: bird migration

gene flow

reproductive success is measured by __________ _________

• the # of surviving offspring than an individual products compared to the number left by others in the population

relative fitness

effects of natural selection can be measured by examining the changes in the:

mean of phenotypes

• selection towards one extreme phenotype

directional

• selection towards the mean and against the extreme phenotypes

stabilizing

• selection against the mean; both phenotypic extremes have the highest relative fitness

disruptive

a type of natural selection that explains why many species have unique/ showy traits

• males often have useless structures simply because females choose that trait

sexual selection

a model used to assess whether natural selection or other factors are causing evolution at a particular locus

• determines what the genetic makeup of the population would be if it were NOT evolving

hardy weinberg equilibrium

5 conditions that must be met in hardy weinberg equilibrium

1. no mutations

2. random mating

3. no natural selection

4. extremely large population size

5. no gene flow

frequency of dominant allele in population

p

frequency of recessive allele in a population

q

percentage of homozygous dominant individuals

p²

percentage of heterozygous individuals

2pq

percentage of homozygous recessive individuals

q²

the ______ genetic diversity in a population, the ______ it can respond to changes in the environment

more, better