ap bio unit 7 population genetics

population

group of species that can produce fertile offspring

gene pool

all copies of every type of allele, populations allele frequencies change over time

where does evolution occur

in populations, not individuals

differential selection

caused by competition

microevolution

small scale genetic changes in population

mutations

irreversible genetic changes, results in genetic variation

genetic drift

the change in frequency of an existing gene variant in the population due to random chance

-most significant to small populations, can cause harmful alleles to be fixed

-doesnt produce adaptations

bottleneck effect

large proportion of population reduced by non selective disaster

ex. floods, famine, fire

founder effect

few individuals became isolated from large population and new small population has differing gene pool

gene flow

transfer of alleles into or out population through fertile individuals or gametes, usually migration

relative fitness

measures reproductive success

number of surviving offspring that an individual produces compared to number left by others

directional selection

one extreme phenotype selected

stabilizing selection

selected towards mean and against extreme phenotypes

disruptive selection

selection against the mean, both extremes

sexual selection

natural selection that explains why species have unique/showy traits

but can sometimes be harmful traits

hardy Weinberg equilibrium

determines what genetic makeup of population would be if not evolved

if population data is the same as hw

population is NOT evolving

if population data is different from hw

population is evolving

hardy Weinberg conditions

1. no mutations

2. random mating

3. no natural selection

4. extremely large population

5. no gene flow

p variable

frequency of dominant allele

q variable

frequency of recessive allele

p²

percent homozygous dominant

q²

percent homozygous recessive

2pq

percent heterozygous

homologous structure

same structure, different function, divergent evolution

analogous structure

same function, different structure, convergent evolution

phylogenetic tree vs cladogram

phylogenetic tree length show change over time

root

common ancestor of all species

sister taxa

clades emerging from same node

basal taxon

lineage that remains unbranched

monophyletic group

includes most recent common ancestor and all descendants

paraphyletic group

includes most recent common ancestor but not all descendants

polyphyletic group

organisms without most recent common ancestor

principle of parsimony

if there is conflict among beliefs, use the one that requires the fewest assumptions/simplest answer is usually true

evidence for evolution

-fossil record

-comparative morphology

-biogeography

species

group able to interbreed and produce viable, fertile offspring

speciation

formation of new species, increases life diversity

allopatric speciation

physical barrier divides population, natural disaster

sympatric speciation

new species evolves while inhabiting some geographic region as ancestral species, usually due to exploitation of new niche

prezygotic barriers

prevent mating or hinder fertilzation

habitat isolation

living in different spaces

temporal isolation

different seasons or time

behavioral isolation

differing sexual behavior or courtship rituals

mechanical isolation

reproductive anatomy doesnt fit

gametic isolation

proteins on gamete surface dont allow for egg and sperm

postzygotic barriers

prevent zygote from developing into viable, fertile adult

reduced hybrid viability

genes of different parents interact in ways that impair hybrids development or survival

example: sheep fertilize goats but embryo dies

reduced hybrid fertility

hybrid can develop into healthy adult but sterile

ex. donkeys and horses

hybrid breakdown

hybrid at first generation fertile but when mate with parent species or one another, offspring sterile

microevolution

change in allele frequencies within single species of population

macroevolution

large evolutionary patterns like adaptive radiation/mass extinction

stasis

no change over long periods of time

punctuated equilibrum

evolution occurs after long period of stasis

gradualism

evolution occurs slowly over hundreds of years

divergent evolution

groups with same common ancestor evolve and accumulate differences resulting in formation of new species

adaptive radiation

if new habitat or niche becomes available, species can diversify rapidly

convergent evolution

2 different species develop similar traits despite having different ancestors analogous traits

extinction

termination of species, human activity affected extinction rates

-quicken during ecological stress

-if species go extinct, opens up niche that is exploited by different species