Biol 304 1st Edition Exam # 3 Study GuideLecture 1 (march 16)Chapter 8Evolution at multiple loci: sex (skipping linkage) Adaptive significance of sex- Many organisms can reproduce both sexually and asexually- Rare in vertebrates, common in other taxaMaynard Smith’s Null Model- Assuming: o 1- female’s reproductive mode does not affect the number of offspring she can haveo 2- female’s reproductive mode doesn’t affect offspring survival - Asexual females should have twice the fitness as sexual ones - Also asexual individuals give 2 copies of each gene to offspring- Male fitness is often highly variableEvolutionary advantages of sex- Genetic recombination - 2 ideas:o Can ”fix” problems caused by mutations and drifto Can increase potential to adapt to changing environmentSex can fix problems from mutations and drift- “muller’s ratchet” : in an asexual population, bad mutations can accumulate due to genetic drift- Over time, the pop. Develops a high “genetic load” : more individuals carry more bad mutations, causing decrease in average fitness in the pop.- This happens even if selection is acting against mutations- Genetic drift acts against selection over time- This only happens over long periods of time, asex. Reproduction increases fitness short termSex can increase adaption to changing environment- Selection on multilocus genotypes- “red queen hypothesis” : antagonistic interactions (predator/prey, host/parasite) exert constant selective pressures. Sexual species have advantage.o Frequency dependent selectiono Arms raceLecture 2 (March 18)Chapter 9Evolution at multiple loci: quantitative geneticsEast’s work on flowering tobacco - Early 1900’s- Trying to confirm Mendel’s work- Studied inheritance of corolla tube length- Found that it was harder than pea plantsEast made 2 predictions concerning floral tube length- If tube lengths of tobacco were controlled by several mendelian traits then:o Parental genotypes would have very low probability of showing up in F2 progenyo Parental genotypes would be recoverable with selective breeding of the F2 progenyEnvironmental influences- Quantitative traits especially likely to show effects of environment- Phenotypic plasticityQTLs = quantitative trait loci- Identifying which loci affect quantitative traits is important for:o Understanding diseases with heritable componento Breeding high yield, pest resistanceo Understanding how ecologically important traits evolveQTL markers- Marker loci that are physically close to the QTLs of interest- QTL markers generally loci that can be “fingerprinted” with techniques such as DNA sequencing or microsatellites- Compare QT phenotypes to marker genotypes to find correlationHeritability- Phenotypic variation (Vp) = total variation in a trait- Heritability = fraction of phenotypic variation in a trait that is due to variation in genes (Vg)- Heritability = Vg/Vp or Vg/(Vg+Ve)- Broad sense heritability- Slope of best fit line gives heritability - Narrow sense heritabilityLecture 3 (March 20)Broad vs narrow sense heritability- B sense = fraction of phenotype variation that is heritable from all genetic sources of heritabilityo Vg/Vp- N sense = estimates the fraction of phenotype variation due additive genetic variation Va(but not dominant genetic variation Vd)o H2 = Va/VpPhenotypic variation - Vp = total phenotypic variation- Vg = total genetic variation- Va = additive genetic variation- Vd = dominant genetic variation- Ve = phenotypic variation due to environment Predicting evolutionary response to selection- R = h2 so H2 is narrow sense heritabilityo S is selection differentialReview Alpine sky pilot and bumblebee case studyLecture 4 (March 23)Directional selection - One extreme is advantageous- Over time, mean value for pop. Moves toward the one extreme Stabilizing selection- Intermediate values of the trait are advantageous- Extremes are bad- Over time natural selection weeds out extremesDisruptive selection- Extremes are good, intermediates bad- Over time, pop. Develops bimodal distribution rather than bell shaped Fisher’s fundamental theorem hypothesis- Rate at which mean fitness of a population increases (from selection) is proportional to the amount of additive genetic variation in traits under selection (narrow sense heritability)Why variation?- Selection is still happening (favorable mutations) - Mutation/selection balance (bad mutation vs elimination by selection)- Disruptive selection may be more commonMisconceptions regarding heritability- Heritable traits can be easily compared among diff. pops.- Reality: heritability estimates are specific to a particular population and environment. They do not tell us why pop. Differ with respects to certain traits. Lecture 5 (March 25)Chapter 10Studying adaptation: evolutionary analysis of form and functionHow do we know if a trait is adaptive?Adaption: - A trait that increases fitness that evolved from natural selection- Not every difference among related taxa/pops. Is an adaption- Not every trait is adaptive- Not every adaptation is perfectHow do we study adaptation?- Experiments – have to test falsifiable hypotheses that rule out non-adaptive explanations - Observational studies – have to test falsifiable hypotheses that rule out non-adaptive explanations - Comparative studies – have ti test falsifiable hypotheses that rule out non-adaptive explanations- Review spider-fly case studyControlled experiments are sometimes infeasible- Some organisms hard to keep in captivity- Legal/ethical obstacles- Can always make a control- Some environments can be made in a lab.Observational studies- Involve observation, descriptions, and measurements takes in natural setting- There isn’t a variable that is controlled by researcher, but there are other ways of testing hypotheses. Comparative methods- Address questions of adaptation using comparisons across species or pop.- Utilize phylogenetic frameworks. Using a phylogenetic framework: Felsenstein’s method- Requires a well- resolved phylogeny of study species- Only phylogenetically independent contrasts should be evaluatedLecture 6 (March 27)Chapter 11Sexual selectionSexual dimorphismSexual selection- Type of natural selection involving traits that affect ability to mate and reproduce- May cause evolution of sexually dimorphic traitsBattle of the sexes- Males and females have diff. strategies in life- Females generally devote more energy to fewer offspring- Males