BI 445 Evolution Terms Definitions Midterm 1 Chapter 7 Population Genetics II Migration movement of alleles between populations Homogenize allele frequencies Counteract natural selection Increase genetic variation in populations Effective 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 population Inbreeding Depression results from exposure of deleterious recessive alleles to selection Number of homozygotes increase and heterozygotes decrease Reduces fitness of populations due to inbreeding Genetic Drift change in allele frequencies in a population resulting from sampling error chance events and finite population sizes Ability to reproduce and survive varies randomly Is not a force for adaptation but is for evolution o Changes in allele frequencies Change in allele frequencies causes it to either drift toward fixation or loss this results in a loss of heterozygosity allele frequency in new population by chance will be Founder effect different from what they were in the source population Sharp reduction in population size Bottleneck effect 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 site o dN dS 1 replacements are deleterious o dN dS 1 replacements are neutral o dN dS 1 replacements are beneficial Testing theory via McDonald Kreitman test o Measure dN dS between two species o Then measure pN pS Ratio of nonsynonymous and synonymous polymorphisms o If dN dS pN pS if selection is pulling favorable alleles to fixation within a species within a population Selection on DNA Sequences Codon Bias synonymous codons not present in equal proportions o 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 mutations o Behaves as a single linkage group no recombination Coalescence merging of genealogical lineages as we trace allele copies backward in time Nonrandom Mating alter genotype frequencies not allele Assortative mating phenotypically similar individuals mate o Produces excess homozygotes Disassortative mating phenotypically different individuals mate o Produces exces heterozygotes Inbreeding mating among genetic relatives o Results in excess homozygotes Chapter 12 Kin Selection and Social Behavior Coefficient of relatedness probability that 2 alleles in 2 individuals are IBD R value varies depending on relationship o Half siblings 1 4 o Full siblings 1 2 o Cousins 1 8 B benefit to recipient C cost to actor r coefficient of relatedness Hamilton s Rule allele for altruistic behavior will spread if Br C Inclusive Fitness direct and indirect fitness Indirect fitness change in relatives fitness due to actors action Kin selection selection for traits that increase indirect fitness Haplodiploidy 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 relatedness o Sister sister o Mother daughter son o Sister brother Example wood ants o Queen lay eggs at 1 1 ratio of sexes o Workers selective neglect or kill eggs based on gender o Hatch ends up being 3 1 favoring females because the females are better to invest in since they are more related Monogamy 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 would Parent Offspring Conflictions Weaning conflict offspring favors own well being over parents Example White fronted bee eaters o Fathers persuade son into helping raise siblings o 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 hatching Siblicide 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 is o Food shortages o Overproduction of offspring Example Booby species o Masked boobies lay 2 eggs and the one that hatches first pushes the other one out of the nest after it hatches and it dies o 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 this o Stable groups o Many opportunities for altruism in life o Good memory o Potential altruist have symmetrical interactions Usually exemplified in long lived and social species Chapter 13 Life History Evolution Diversity in Reproductive Strategies Semelparous reproduce once and die Iteroparous reproduce multiple times Life History Pattern Pattern of energy allocation to growth vs reproduction from birth to death Tradeoff between growth and reproduction o 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 life Rate of Living Theory of Aging Assumes aging is caused by irreparable tissue and cell damage 2 assumptions o Aging is proportionate to metabolic rate False assumption o Species cannot evolve longer life spans without decreasing metabolic rate True species can evolve longer life spans Example drosophjla selection experiments Evolution theory of Aging Aging is caused by failure to repair tissue and cell damage 2 hypothesis o Mutation Accumulation Selection is weak against deleterious mutations expressed late in life Late acting deleterious alleles maintained at high levels by mutation selection balance o Antagonistic pleiotropy Mutations that produce benefits early in life and cost later in life may be favored by selection Tradeoff Early and Late Reproduction Collared Flycatcher Eggs o Too many too early reduces output