BIO111 unit 1

evolution

change in allele frequencies in a population over time

allele frequencies

occurrence of an allele in a population expressed in a proportion out of an entire population

genetic variation

Darwin proposed that natural selection led to changes in allele frequencies

population genetics

study of properties of genes in a population

quantifying natural selections with Hardy Weinberg

predicts genotype frequencies in a population

hardy-weinberg equililibruim

proportions of genotypes do not change in a population as long as these conditions are met:
no mutation takes place (unlikely, as mutations are uncontrollable)

no genes are transferred to or from other sources / no immigration or emigration
mating is random (not genetically or phenotypically chosen)

the population is large in size
no selection occurs

hardy weinberg equation

p + q = 1

p (hardy-weinberg)

frequency of dominant allele

q (hardy weinberg)

frequency of recessive allele

p²

frequency of homozygous dominant individuals

q²

frequency of homozygous recessive individuals

2pq

frequency of heterozygote individuals

what does the 2 in 2pq stand for?

the 2 ways to get a heterozygote alleles

hardy-weinberg equation to find the % of alleles

p² + 2pq + q² = 1

populations will vary if:

natural selection is acting on one phenotype over another
individuals are utilizing mate choice based traits
theres immigration/emigration

mutations are occurring

agents of evolutionary change

mutation, gene flow, nonrandom mating, genetic drift, selection

mutation

ultimate source of genetic variation, rates are generally low because mutations can be fixed when caught or dont change phenotype

gene flow

movement of alleles from one population to another. ex. animal movement (immigration/emigration), drifting pollen

nonrandom mating

mate choice, can increase or decrease variation in populations

assortive mating

phenotypically similar individuals mate, genotypes can differ greatly from the Hardy-Weinberg principal (can produce excess of homozygotes)

disassortive mating

phenotypically different individuals mate, produces excess of heterozygotes

genetic drift

changes in allele frequency by CHANCE alone. can lead to allele loss in isolated populations where uncommon alleles are vulnerable

founder effect

few individuals disperse and start a new population which leads to loss of diversity (missing alleles) by unintentionally isolating.

bottleneck effect

drastic reduction in population size due to natural forces where survivors are the entire gene pool, leading to diversity loss (even with population re-growth).

artificial selection

breeder Selects desired characteristics

natural selection

environment determines reproduced traits. requires variation with a genetic basis to select for or against, must be lasting. Phenotype MUST vary

sexual selection

competition for mates. favors some geno/phenotypes over others. Good traits have more reproductive success and more offspring to spread to the next generation. without those traits → no reproduction and the traits eventually disappear

fitness

individuals with one phenotype leave more surviving offspring than individuals with an alternate phenotype. the most “fit” phenotype produces the most offspring

reproductive strategies

females evaluate a males quality and then decide whether to mate, theyre more selective because females birth a limited amount at a time and they spent more time caring for the offspring. males increase their fitness by mating with as many females as possible. in the case of biparental care, both sexes are picky

intRAsexual selection

competition between members of one sex

intERsexual selection

mate choice

secondary sexual characteristics

antlers, horns, colored feathers, traits to “persuade” members of the opposite sex

sexual dimorphism

differences between sexes

sperm competition

competition among sperm to successfully fertilize an egg

sensory exploitation

evolution in males of a signal that exploits preexisting biases

frequency dependent selection

fitness of a phenotype depends on its frequency within the population

negative frequency-dependent selection

rare phenotypes are favored

positive frequency-dependent selection

common phenotypes are favored

oscillating selection

selection favors one phenotype at once and another at a different time, this will maintain genetic variation

heterozygote advantage

maintains both alleles in the population (ex. sickle cell amenia)

genetic variation

many traits affected by more than one gene. selection can act on all genes for that trait, changing the population depending on which geno/phenotypes are favored

disruptive selection

favors BOTH extreme phenotypes

directional selection

favors ONE extreme phenotype

stabilizing selection

favors the INTERMEDIATE phenotype

industrial meninism

phenomenon where darker individuals become predominant over lighter ones

fossils

preserved remains of once-living organisms. a rare event that requires:
organisms buried in sediment
calcium in bone or other hard tissue
surrounding sediment hardens to form rock

fossil dating methods

relative dating and isotopes.

relative fossil dating

dating fossils based on how old surrounding materials are

isotopic fossil dating

degradation of atoms into various forms

transition fossils

intermediate forms of organisms demonstrating links between older and newer species, they help fill the gaps in the fossil record

homologous structures

structures with different appearance and function, derived from a common ancestor (ex. forelimbs)

analogous structures

structures with similar structure/function with different evolutionary history (human tailbone vs money tail)

vestigial structures

no apparent function, but resembles structures possessed by ancestors (ear wiggling muscles in humans vs other mammals)

embryonic development

embryos of different vertebrates often resemble each other in early stages and differentiate as they get older

pseudogenes

copy/trace of a gene thats not transcribed/expressed

biogeography

study of geography distribution of species

convergent evolution

evolution in similar patterns but in different areas