AP BIO: Unit 7

evolution

a change in the genetic makeup of a population over time and is supported by multiple lines of evidence

natural selection

the process in which the organisms best adapted to their environment tend to survive and produce more offspring; one of the major mechanisms of evolution (Charles Darwin) The

Factors for evolution

1. genetic variablity

2. competition

3. better adapted phenotypes

4. differential reproductive rates

genetic variability

variation may come from sexual reproduction (random fertilization, crossing over, and independent assortment), mutations, and immigration

competition

when organisms struggle for resources leading to differential survival

selective pressures

abiotic/biotic factors that impact survival; certain environments will select best traits to be passed down

fitness

the ability to survive to reproductive age, find a mate, and produce offspring

Biological fitness

more offspring= more bio fitness; fitness doesn’t equal strength

reproductive success

production of offspring

adaptation

certain traits that give an advantage for survival

heritability

the ability to pass on adaptations to successful generations

modern def of evolution

a change in allele frequency/genetic makeup of a population over time; supported by multiple lines of evidence

artificial selection

humans actively choose which traits should be passed onto offspring

stabilizing selection

towards the mean against extremes (mostly stable)

directional selection

towards one extreme (consistent change in the environment)

disruptive or diversifying selection

against the mean, toward both extremes (sharp differences in the nature of the environment)

predation selection

act on both predator and pray; they try to evolve to yk eat or survive (camouflage, mimicry, speed)

coevolution

two or more species reciprocally affect each other’s evolution (predator-prey, competition, symbiosis)

physiological selection

acts on body functions/structures (disease, resistance, morphology0

IMPORTANT!!

Populations evolve, individuals DO NOT

population genetics

the science that studies that trait variation rates over time within a population

Four Population Criteria

1. same species of organisms

2. located in the same location

3. at the same time

4. and showing signs of reproduction

Hardy Weinberg/ Genetic Equilibrium

a theoretical condition in which a population’s genotype and allele frequencies remain unchanged over generations; can be used to describe and predict allele frequencies in a nonevolving population

REQUIREMENTS FOR HARDY WEINBERG

1. No mutations

2. No gene flow

3. Must have large population (to avoid genetic drift)

4. no natural selection

5. random mating no sexual selection

Gene flow

transfer of alleles into or out of a population due to immigration or emigration (seed and pollen distribution)

genetic drift

unpredicted changes in allele frequencies due to chance usually occurs in small, isolated populations; smaller a population—> larger efffect of loss in genetic variation

-result in a decrease in genetic variation within a given population= decrease in variation can increase the differences between populations of the same species

sexual selection

when individuals with certain inherited characteristics to mate more likely

mutations

result in the formation of new alleles/increased genetic variation within the population; a random change in an organism’s genome

the founder effect

occurs when a new colony is started by a few members of the original population; small population may have reduced genetic variation from the og pop, a non-random- sample of the genes in the og pop

bottleneck effect

genetic drift resulting from reduction of a population due to a natural disaster or human activity; not representative of the original population

small pop vs. large pop

small pop with less genetic variation = more susceptible to random environmental impacts and less able to adapt to them than larger pop with more genetic variability