BI 445 Evolution Terms/DefinitionsMidterm 1Chapter 7: Population Genetics IIMigration— movement of alleles between populations- Homogenize allele frequencies- Counteract natural selection- Increase genetic variation in populationsEffective Population Size— size of an ideal theoretical population that would lose heterozygosity at the same rate as an actually population of interest- Ne = (4 Nm Nf) / (Nm + Nf)- Only includes population that participates in reproducing- Different numbers of each sex in a populationInbreeding Depression— results from exposure of deleterious recessive alleles to selection- Number of homozygotes increase and heterozygotes decrease- Reduces fitness of populations due to inbreedingGenetic Drift— change in allele frequencies in a population resulting from samplingerror (chance events) and finite population sizes- Ability to reproduce and survive varies randomly- Is not a force for adaptation but is for evolutiono Changes in allele frequencies Change in allele frequencies causes it to either drift toward fixation or loss, this results in a loss of heterozygosity- Founder effect — allele frequency in new population by chance will be different from what they were in the source population- Bottleneck effect — Sharp reduction in population size Neutral Theory— neutral mutations that rise to fixation by drift vastly outnumber beneficial mutations that rise to fixation by natural selection- Testing neutral theory via mutation rate of non- and synonymous substitutions per siteo dN/dS < 1 — replacements are deleteriouso dN/dS = 1 — replacements are neutralo dN/dS > 1 — replacements are beneficial - Testing theory via McDonald Kreitman testo Measure dN/dS between two specieso Then measure pN/pS Ratio of nonsynonymous and synonymous polymorphisms within a specieso If dN/dS > pN/pS if selection is pulling favorable alleles to fixation within a populationSelection on DNA Sequences- Codon Bias— synonymous codons not present in equal proportionso Most prevalent in frequently transcribed genes - Hitchhiking (selective sweep)— occurs when strong positive selection acts on a particular amino acid change o Linked neutral mutations swept along with beneficial mutationso Behaves as a single linkage group (no recombination) Coalescence— merging of genealogical lineages as we trace allele copies backward in timeNonrandom Mating (alter genotype frequencies, not allele)- Assortative mating— phenotypically similar individuals mateo Produces excess homozygotes- Disassortative mating— phenotypically different individuals mateo Produces exces heterozygotes - Inbreeding— mating among genetic relatives o Results in excess homozygotes Chapter 12: Kin Selection and Social BehaviorCoefficient of relatedness— probability that 2 alleles in 2 individuals are IBD- R value varies depending on relationshipo Half-siblings = 1/4 o Full siblings = 1/2 o Cousins = 1/8 Hamilton’s Rule— allele for altruistic behavior will spread if Br > C- B = benefit to recipient- r = coefficient of relatedness- C = cost to actorInclusive Fitness— direct and indirect fitness- Indirect fitness— change in relatives fitness due to actors actionKin selection— selection for traits that increase indirect fitnessHaplodiploidy Theory in Hymenoptera — females should altruistically favor production of sisters rather than their own offspring because of how closely related they are- Males are haploid and develop from unfertilized eggs- Females are diploid and develop from fertilized eggs- Coefficient of relatednesso Sister-sister = ¾o Mother-daughter/son = ½o Sister-brother = ¼ - Example: wood antso Queen lay eggs at 1:1 ratio of sexeso Workers selective neglect or kill eggs based on gendero Hatch ends up being 3:1 favoring females because the females are better to invest in since they are more relatedMonogamy Hypothesis— when an individual can be certain that future siblings will be full siblings, it will increase an individual’s inclusive fitness just as much as an offspring wouldParent-Offspring Conflictions- Weaning conflict— offspring favors own well-being over parents- Example: White-fronted bee eaterso Fathers persuade son into helping raise siblingso Harass sons via Chasing resident birds off territory Physically prevent food transfer during courtship feeding Repeatedly visit nests that aren’t theirs before egg layer or hatchingSiblicide— sibling will kill other siblings while parents watch passively- Increases fitness of surviving sibling and increases attention from parent- Can be adaptive to reduce brood size when there iso Food shortageso Overproduction of offspring- Example: Booby specieso Masked boobies — lay 2 eggs and the one that hatches first pushes theother one out of the nest after it hatches and it dieso Blue-footed boobies Doesn’t instantly kill other sibling, but when food shortage continues for long period, the older hatchling will attack and kill the younger sibling- Fitness = (# of young) * (per-capita survival of young)Reciprocal Altruism— exchange of favors that ultimately benefits both individuals- Conditions that favor thiso Stable groupso Many opportunities for altruism in lifeo Good memoryo Potential altruist have symmetrical interactions- Usually exemplified in long-lived and social speciesChapter 13: Life History EvolutionDiversity in Reproductive Strategies- Semelparous: reproduce once and die- Iteroparous: reproduce multiple timesLife History Pattern- Pattern of energy allocation to growth vs. reproduction from birth to death- Tradeoff between growth and reproductiono Natural selection optimizes growth vs. reproduction to yield highest total fitness. Senescence— late-life decline in fertility and survival- Trade off between reproduction early in life and tissue repair late in lifeRate of Living Theory of Aging- Assumes aging is caused by irreparable tissue and cell damage- 2 assumptionso Aging is proportionate to metabolic rate False assumptiono Species cannot evolve longer life spans without decreasing metabolic rate True, species can evolve longer life spans Example: drosophjla selection experimentsEvolution theory of Aging- Aging is caused by failure to repair tissue and cell damage- 2 hypothesiso Mutation Accumulation  Selection is weak against deleterious mutations expressed late in life Late acting deleterious alleles maintained at high levels by mutation-selection balanceo