evolution exam 3

quantitative traits

continuous distribution, polygenic, affected by environmental factors, average trait value across all environments, more loci=more continuous 

additive gene action

each additional copy of target allele changes the phenotype, ex. A, B, C each additional copy darkens wheat color

GxE effect

determine differences in slopes of fitness in each genotype

genetic effect, G

average of individuals phenotype across environment, expected phenotype from the genotype, compare average across environments to determine presence or absence of effect

environmental deviation, E

deviation from genetic effect, close to 0 means no effect from external environment, compare average fitness in each environment to determine presence or absence of effect

nonadditive gene action

dominance and epistasis, less likely selection effects based on no phenotypical differences in varying genotype

phenotypic variance Vp

total variance in the trait, Vg+Ve

genetic variance Vg

variation among individuals in phenotypic trait explained by differences in alleles, Va+Vd+Vi

environmental variance Ve

variation among individuals in phenotypic trait explained by differences in environment

interpretation of phenotypic variance

large Vp means genetics play a large role in the variance seen in a population, smaller Vp means genetics play small role in variance seen in a population

broad sense heritability H²

proportion of Vp in the population due to all types of genetic differences, Vg/Vg+Ve, closer to 0-environmental differences, closer to 1-heritable differences

nonadditive gene action offspring vs parent

offspring will have different average in trait than the parent average

additive gene action offspring vs parent

parent and offspring will have same average in trait

narrow sense heritability h²

smaller than broad sense, Va/Va+Vd+Vi+Ve, slope of graph comparing mean parent and mean offspring trait, doesn’t tell if trait is genetically determined, population and environment specific, variation in additive gene action

selection coefficient, s

1-w, looks at one loci

selection differential, S

strength of selection on quantitative traits, average fitness-average fitness of survivors, without environmental effect offspring will have same avg fitness as survivors

Breeder’s equation

R=h²S, calculate response to selection

directional selection

straight line of regression comparing trait to relative fitness

stabilizing selection

decreasing variance, same mean, shift toward the mean

diversifying selection

increasing variance, same mean, shift toward the extremes

phenotypic correlation rP

ranges from -1 to 1, hxhyrA + exeyrE

pleiotrophy

singe gene affects multiple phenotypes

genetic correlation rA

selection can cause correlation between traits with pleiotrophy or linkage of specific traits

environmental correlation rE

two correlated traits that are expressed in certain environments, ex. temperature impacts wing length and width

environmental variance underlying trait

e²= 1-h²

selection on correlated traits

difficult to determine which of the correlated traits is being selected for, separate with total selection on trait

total selection

direct and indirect selection on correlated traits, S1=B1+B2r12+B3r13, hold other units constant to determine direct selection B

selection gradient B

measures direct selection on trait

reciprocal transplant experiment

determine GxE effects, examine both genotypes in each environment

common garden experiment

raise different phenotypes in singular environment, insight on G effects, not equipt for local adaptation unless mimic E in lab

gamete size

sperm, small gametes, egg, large gametes

sex not defined by

sex determination mechanisms, extremely variable genetic, social, and environmental conditions

species variation in sex determination

female only species, hermaphroditic species, sex changing species

reproductive handicap model

Smith, assumes reproductive mode (asexual vs sexual) doesn’t affect how many offspring or the probability of survival, favors asexual selection

twofold cost of sex

males inefficient and wasteful, don’t directly produce offspring

genetic load

accumulation of deleterious mutations in asexual populations, average number of mutations in population

benefits of sex

purge deleterious mutations from population, sex accelerates adaptive evolution (Fisher Muller hypothesis)

Muller’s ratchet

drift and mutation increase genetic load in asexual population, sex creates favorable multilocus genotypes lost to drift via recombination

purifying selection

more synonymous mutations than nonsynonymous, eliminates deleterious mutations

red queen hypothesis

ossiclations in relative fitness of asexual lineages when parasites are present, short time lag between emergence ……, positive correlation between parasite load and sexual selection

environmental unpredictablity hypothesis

sexual selection responds to unpredictable environmental change

tangled bank hypothesis

various niches in environment, more niches leads to more sexual selection

parasite load hypothesis

more sexual selection expected when the parasite load is high to select for favorable traits against parasite

anisogamy

large and small gamete types

isogamy

similar gamete sizes

bigger games

put in energy, quality over quantity, more parental efforts

small gametes

more mobility, quantity over quality, more mating efforts

asymmetry of sex

trade off between gamete size and amount, selection operates differently for different sexes

sexual dimorphism

different phenotypes in each sex for success, gamete structure, morphology, physiology, behavior

intrasexual selection

selection from competition between individuals of the same sex, more common in males, combat, weaponry, mating tactics, infanticide, sperm stamina/amount

intersexual selection

selection from individual of 1 sex choosing mates of the other, more common in females, visual, calls, behavior