biol 191

descent with modification

organisms originate from common ancestors but accumulate changes over generations; not within their lifetime

artificial selection

humans choosing which organisms reproduce based off their traits

natural selection

organisms with heritable traits survive and reproduce at better rates because their traits benefit their environment

adapation

an inherited characteristic that increases an organisms ability to survive and reproduce; trait that results from selection

three key factors of natural selection

must be variation, must be heritable, must affect fitness (reproductivity)

homology

similiarity between characteristic bc of shared ancestry

homologous structures

structures found across species bc they were inheritied from a common ancestor; structure may have a different function across species

evolutionary relationship of homology and homologous structures

organisms are evolutionarily related

convergent evolution

similar features evolve independently in different evolutionary lineages

analogous structures

similar features exist bc of convergent evolution rather than common ancestry; birds and insects both have wings and perform similar function but they are not evolutionarily related

fossils

evidence of organisms that lived in the past and see change through time

biogeography

study of geographic distriubution of species

phylogeny

evolutionary history of a species or groups of related species

how was phylogenies used

determine evolutionary relationships, identifiy common ancestors, compare how close related organisms are

binomial scientific names; how does it work

Format: genus species; genus it capitalized and species is lowercase and both are italicized

ancestral character

a trait inherited from an ancestor that is not unique

derived character

a newer evolutionary trait that arose in a particular lineage

monophletic group

one complete group

paraphyletic group

partial group

polyphletic

pulled from multiple unrelated branches

maximum parsimony

simplest explanation is the best; choose the tree with fewest evolutionary changes

evolutionary relationships using phylogenetic trees

two organisms that share a recent common ancestor are more closely related; sister taxa are each other’s closet relatives because they share an immediate common ancestor.

molecular clock

estimates how much time has passed based on the amount of evol. change in genetic material

horizontal gene transfer

when genes move from one genome to another rather than being passed from parent to offspring

genetic variation

differences among individuals in their genes/DNA; evolution depends on this

causes of genetic variation

mutations, crossing over, independent assortment, fertilization

population

organisms

gene pool

all copies of all alleles present in a population

hardy-weinberg equilibrium

a null model used to determine whether evolution is occurring; if allele frequencies remain constant the population is in equilibrium

five conditions of hardy-weinberg

no mutations, random mating, no natural selection, very large/infinite population, no gene flow; if a condition is violated allele frequency can change and evolution is occurring

genetic drift

random chance

gene flow

movement of alleles between populations

founder effect

small number of organisms leaving a large population and establishing a new population; allele frequency may not represent original population; few individuals start a population

bottleneck effect

a population suddenly becomes smaller bc of an event or disaster; survivors may not reflect original population genetically wise; population gets reduced

effects of genetic drift

1. allele frequencies to change randomly

2. loss of genetic variation

3. alleles become fixed

4. potentially harmful alleles become fixed

5. genetic drift is powerful in small populations

relative fitness

an individual genes contribute to next generation compared w/ other individuals

directional selection

one extreme phenotype has greater fitness; population shifts towards one extreme

disruptive selection

both extremes have greater fitness than the middle

stabilizing selection

middle is favored