BIOL 201 1st Edition Lecture 3Outline of Last LectureI. Hardy-Weinberg Equilibriuma. AssumptionsII. MHC Loci Examplea. Possible ExplanationsIII. HeterozygosityIV. Continuous Traitsa. Meanb. Variancec. Coefficient of Variationd. CorrelationV. Variation a. Phenotypicb. GenotypicVI. Heritability a. Broad sense vs. Narrow senseVII. Brief history of evolutionary thoughta. Greeksb. Christian Theologyc. Pre-Darwinian evolutiond. Charles DarwinOutline of Current LectureI. Darwin’s theory of Evolution by Natural SelectionII. Antibiotic ResistanceIII. Selection & the Hardy-Weinberg equilibriumIV. Fitnessa. Computing fitnessV. Adaptive landscapeVI. Selectiona. For recessive allelesb. For dominant allelesc. For codominant allelesVII. Change in allele frequency due to selectionVIII. When evolution is fastIX. Maintenance of Polymorphisms a. Temporal fluctuationsb. Spatial fluctuationsc. Inverse frequency-dependent selectionCurrent LectureI. Darwin’s theory of Evolution by Natural Selectiona. Traits show variation.i. Heritable variation is necessary for evolution.b. Some variation is heritable.i. Heritable variation is necessary for evolution.ii. Not all variation is important for evolutionc. Individuals differ in fitness.d. There is a correlation between phenotype and fitness.i. Natural selection can occur without evolution. ii. Natural selection is change in phenotypes between a generation but whether or not this change goes to the next generation is how you determine if evolution is occurring.iii. Evolution by natural selection requires phenotypic variation.iv. Evolution can occur without natural selection because it can also occur due to genetic drift and migration.v. Natural selection does NOT require genetic variation.II. Antibiotic Resistance: example of evolution by natural selection, can be observed easily because bacteria reproduce so quicklya. Genetic mechanisms:i. Alteration of the target siteii. Blockage of uptakeiii. Detoxification of drugiv. Develop alternative biochemical pathwaysv. Evolve decreased requirements for products of blocked pathwaysIII. Selection & the Hardy-Weinberg equilibriuma. Selection causes a violation of the Hardy-Weinberg equilibrium because it changes the frequency of the dominant and recessive alleleb. Some of the initial population dies and leads to different proportions of each genotypeIV. Fitness: how well an organism survives and reproduces; to get genes into the next generationa. Fitness: survival times reproduction; = probability of survival from birth to reproduction X average fecundityb. Computing fitness: have to sum up the number of individuals across generations due to survival and reproductionc. Relative viability: survival component of measure of fitness, divide # organisms that survived by the initial # of organismsd. Relative fecundity: the reproduction component of fitness, # offspring divided by the # of parents e. divide # offspring by the # of zygotes in the beginning to get total fitnessf. may be asked to scale so that one of the relative viabilities equals oneV. Adaptive landscape: looks like topography map and looks across 2 traits to show the fitness given by the combination of the twoa. Character example: bill depth or wing length of a birdb. Height of the “mountain” is the fitnessVI. Selectioni. s= selection coefficient, measured by going into a population and determining fitness out in population, is positive unless told otherwiseii. You figure out if something is dominant or recessive by looking at fitness. The one that has the same fitness as the heterozygoteis the dominant oneiii. The recessive trait isn’t always selected againstb. For recessive allelesc. For dominant allelesd. For codominant alleles: additive inheritance, nothing is dominantVII. Change in allele frequency due to selectiona. Faster evolution occurs with stronger selectionb. Fixation: frequency of 100%c. Higher s value means stronger selectionVIII. When evolution is fasta. With stronger selection and genetic variation is highb. Evolution is slow when alleles are rare because you need variation to get faster evolution and when alleles are rare you have less variationc. There’s the most variation when the s value is closest to 0.5IX. Maintenance of Polymorphisms i. Polymorphism: more than one allele around at one locusii. Selection tends to erode variation so the question of how polymorphism is maintatined is a big oneb. Temporal fluctuations: happens often due to weather changes, like drought causing changes in seed availability  lead to beak size changes in birds because seeds also became harderc. Spatial fluctuations: like wet and dry patches of a meadow with plants that can’t move through space on their ownd. Inverse frequency-dependent selection: also called negative frequency-dependent selectioni. Selection is dependent on the allele frequencies in such a way that rare alleles are favoredii. Cryptic: hard to see in environmentiii. Whatever form is more common is the one that’s taken more by predator regardless of whether they are more or less crypticiv. So rare ones regardless of phenotype have selective advantage until they become more