Microevolution

modern synthesis theory: Neo-Darwinism, expanded understanding of evolution, consider genetic basis of inheritance
- combines natural selection, mendelian genetics, and population genetics
- evolution: any change in allele frequency
biological species concept: a “species” can interbreed and produce viable, fertile offspring
hardy weinberg equilibrium: hypothetical, allele frequencies don’t change between generations, used for comparison
- formula: p² + 2pq + q² = 1 & p + q = 1
- p² = frequency of homozygous dominant, q² = frequency of homozygous recessive, 2pq = frequency of heterozygous, p = dominant allele frequency, q = recessive allele frequency
gradualism: incremental environmental change over a long period of time
punctuated equilibrium: evolution occurs through rapid episodes of speciation, with long periods of little change in between

acts on phenotypes, ad therefore genotypes, of a population
fitness: ability to survive and reproduce in the organism’s environment, genotypes that contribute to this are more fit
genetic variation: caused by mutations and sexual reproduction
types of selection
- directional: favors one phenotype over another
- disruptive: favors both extreme phenotypes
- stabilizing: favors intermediate phenotype
relative fitness: measures reproductive success of an organism by comparing its # of its offspring to the average # of offspring in the population

microevolution: change in an allele frequency of a population over a short period of time
genetic drift: change in frequency of traits in a population due to random/chance events, smaller populations are more affected
- founder effect: new population started by a small group of a population, eventually evolve into a new species
- bottleneck effect: large population and gene pool drastically reduces b/c of a random disaster (famine, flood, habitat loss, etc.)
- gene flow: change in allele frequency caused by immigration/emigration
mutations introduce new traits/genes to populations that are then selected on and can cause evolution
nonrandom mating: sexual selection, change in traits frequency due to gender preferences

adaptive radiation: rapid diversification of an ancestral species into many new species
stable gene pool: achieved with large population, random mating, no significant migrations, no large scale mutations
types of evolution
- convergent: similar environmental pressure → similar adaptations in unrelated species (analogous traits, homoplasy)
- divergent: related organisms diverge in traits b/c they experience different environmental pressures
speciation
- allopatric: physical barriers isolates populations
- sympatric: population remains in the same geographic area but is reproductively isolated b/c of other factors
- parapatric: new niche forms in the environment, part of the population fills the new niche, creates new species
reproductive barriers
- prezygotic: before fertilization, ex. habitat, temporal, behavioral, mechanical, and gametic isolation
- postzygotic: after fertilization, ex. reduced hybrid fertility, reduced hybrid viability (physically weak), hybrid breakdown

embryology: similar embryonic development in closely related organisms
fossil record: shows change in phenotype of a population over years
homology: features with similar structure and position in related organisms, have common ancestor
- homologous structures: shared embryonic tissue develop into different structure in related species b/c different environmental pressures (similar tissues, different functions)
vestigial organs: structures with little to no function, leftover remnants of ancestral species
biochemistry: investigates how biological molecules diversify