Bio– Evolution

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natural selection

species altered overtime due to environmental influences

inherited variations

individuals in a species are different

competition

usually more individuals in an environment than can be supported, leads to competition for resources

adaption

traits that make an organism MORE LIKELY to survive & reproduce

fitness

how well an organism can survive and reproduce in their environment– better adaptions=greater fitness

selection

individuals w/ greater fitness are more likely to survive & therefore reproduce, passing their adaptations to future generations

single gene-trait

trait controlled by one gene

polygenic trait

trait controlled by 2+ genes

stabilizing selection

“average phenotype” becomes more common overtime

directional selection

1 “extreme” phenotype becomes more common overtime

disruptive selection

both “extreme” phenos become more common overtime, may lead to speciation

genetic equilibrium

a population must not be evolving– when disturbed, a population is evolving

hardy-weinberg principle

allele frequency should remain constant in a population unless “disturbing factors” cause them to changeto

to remain in genetic equilibrium, a population must:

1) be large

2) randomly mate

3) not migrate

4) not have new mutations

5) not experience natural selection

hardy-weinberg equation

p+q=1 (for allele frequencies)

p=frequency of dominant allele, q=recessive

p^2+2pq+q^2=1 (for genotype frequencies)

p^2=frequency of homoY

sexual selection

when mate selections are based on traits, not random

genetic drift

changes in allele frequencies due to chance events

founder effect

when a few individuals migrate and establish a new, reproductively isolated population

bottleneck effect

when a sudden unexpected event causes a sudden, drastic reduction in population size

gene flow

migration of individuals in/out of a population

mutations

very low rates, doesn’t usually alter evolution unless paired with another mechanism

common descent

all living things are related to some extent via common ancestors

descent w/ modification

each generation of a population is slightly different than the previous

evolution

any heritable change in a population across the span of many generations

divergent evolution

species develop more different traits over time as a result of different environmental changes/pressures

convergent evolution

species develop more similar traits over time due to shared environmental changes/pressures

coevolution

species “pressure” one another into evolving due to close interactions

evidence for evolution

1) direct observations of populations

2) anatomy

3) embryology

4) molecular biology

5) fossils

6) biogeography

homologous structures

similar in structure & SOMETIMES function, inherited from common ancestor

analogous structures

similar function but not structure, no common ancestor

vestigial structures

features leftover from ancestors that no longer serve a purpose

species

a population whose members have the potential to interbreed in the WILD and produce FERTILE offspring

speciation

divergent evolution of an ancestral species into new descendant species

reproductive isolation

species unable to interbreed for some reason

anatomical isolation

can’t reproduce due to different reproductive organs

behavioral isolation

can’t reproduce due to different courtship rituals

gametic isolation

can’t reproduce due to sperm & eggs being unable to fertilize

geopgrahic isolation

can’t reproduce due to the presence of a physical barrier

habitat isolation

can’t reproduce due to living in different environments and not interacting

temporal isolation

can’t reproduce due to different times of year that they do so

pre-zygotic isolation

something prevents species from breeding

post-zygotic isolation

something prevents offspring from surviving/being able to reproduce at all

gradualism

evolution occurs through slow, consistent changes that add up over a long period of time reflecting a slowly changing environment

punctuated equilibrium

evolution occurs due to sudden, rapid changes reflecting a rapidly changing environment

taxa

species of interest on a cladogram

node

place where two species’ ancestry meets on a cladogram

MRCA

most recent common ancestor

ancestral trait

trait closest to cladogram root, present in all species on cladogram

outgroup

least closely related to other species on cladogram

clade

group of organisms & their MRCA

derived traits

traits developed after ancestral trait, possessed by SOME species on cladogram