AP Bio Unit 7

genetic variation

every population has individuals with slightly different traits due to genetic variations arising from mutations, which are the raw material for natural selection to act upon

overproduction of offspring

more offspring than an environment can support leading to competition for resources like food and mates

competition for resources

due to overproduction, individuals must compete for limited resources, creating a “survival of the fittest” environment

differential survival and reproduction

individuals with more favorable traits/phenotypes to their environments are more likely to survive and reproduce, passing on those advantageous traits to their offspring

artificial selection

when humans can modify an organism by selecting desired traits and breeding them; the domestication of dogs from wolves

an example of evolution as an ongoing process in all living organisms

drug resistant bacteria; a population of bacteria continuously adapts to the presence of antibiotics, leading to strains that are increasingly difficult to treat with existing medications

homologous structures

similarities in characteristics from common ancestryf

fossils

transition species, show a succession of organisms over a long period of time

vestigial structures

modern animals may have structures that serve little or no function; human appendix

molecular evidence

comparing DNA and protein structures between organisms because we share the same basic genetic material, genetic code, and mechanisms for gene expression

biogeographical

the geographic distribution of species, species who live closer together (eg; in North America) are more closely related than species who live farther away (eg; North America vs Asia)

the conditions needed for a population to be in Hardy-Weinberg equilibrium

large population size, no mutations, no migration, random mating, and no natural selection

no selection

no traits are more beneficial to survive

no mutation

gene pool stays the same

no migration

no new genes

large population

less chance of flunctuations

random mating

no traits are preferred

genotype frequency

p²+2pq+q²=1

allele frequency

p+q=1

p

frequency of the dominant allele in the population

q

frequency of the recessive allele in the population

p²

homozygous dominant individuals in a population

2pq

heterozygous individuals in a population

q²

homozygous recessive individuals in a population

bottleneck effect

a sharp reduction in population size due to environmental events or human activities, leading to a loss of genetic diversity

founders effect

small group starts a new population resulting in reduced genetic variation; amish people

genetic drift

random changes in allele frequency

gene flow

migration

directional selection

favors one extreme trait over others; peppered moths during industrial revolution

stabilizing selection

favors the average trait (human birth weight)

disruptive selection

favors both extremes; light and dark crabs can both hide on light and dark rocks from predators

sexual selection

traits increase reproductive success; male peacocks flash their tails at females to mate

biotic factors on evolution

vegetation, predators, prey

abiotic factors

soil, temperature, climate conditions

stable environments

lower rate of evolution; constant selective pressures

fluctuating environments

higher rate of evolution; new selective pressures

convergent evolution

occurs when unrelated organisms evolve similar traits due to environmental pressures; not artificial selection, but still involves selection pressures shaping traits

speciation

formation of new species

phylogenetic trees

diagrams that show evolutionary relationships among species based on common ancestry

out group

species that is least closely related to others in a phylogenetic tree

shared traits

traits found in multiple species

derived traits

traits inherited from a common ancestor that distinguish groups

biological species concept

a definition of species based on reproductive isolation, where members of a species can interbreed and produce fertile offspring

punctuated equilibrium

rapid bursts of evolution followed by long periods of no change, often occurs after mass extinctions or environmental changesg

gradualism

evolution occurs slowly and steadily over long periods, small genetic changed accumulate, eventually leading to speciation

allopatric speciation

occurs when a physical barrier separates populations; mountains, rivers, islands

sympatric isolation

no physical barriers, occurs within the same geographic area due to disruptive selection and mating preferences

pretzygotic isolation

before fertilization, habiitat, temporal, behavioral, mechanical, gametic isolation

postzygotic isolation

after fertilization; embryo fails to develop or offspring are sterile

Permian-Triassic Extinction ("The Great Dying")

252 MYA, likely due to volcanic eruptions, ocean chemistry changes, and climate shifts, 90% of pop wiped out

Cretaceous - Paleogene Extinction

66 MYA, , asteroid impact, dinosaur extinction allowed mammals to dominate

RNA world hypothesis

RNA was likely the first self replicating molecule; some modern RNA molecules (ribozymes) can act as enzymes

adaptive radiation

the rapid evolution of diversely adapted species from a common ancestor, often following a mass extinction or new habitat availability