Merger of Darwin and MendelBREAKING THE SELECTION PLATEAUPowerPoint PresentationSlide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Don’t Need to Know ThisSlide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Video by Ken MillerToday’s Critics of DarwinSlide 27Slide 28Slide 29Slide 30Slide 31Merger of Darwin and MendelI. Dilemmas for DarwinA. Stability and Effectiveness of Change1. Natural selection is limited in its effectiveness-artificial selection reaches a limit in which the trait value can no longer be extended2. Small differences are not large enough-different species have entire suites of characters that differ between themBREAKING THE SELECTION PLATEAUEffectiveness of Natural SelectionCastle’s selection experiment-artificial selection on “racing stripe” width in hooded ratsGenerations5 10 15 20 25Stripe Width (cm)5 10 15 20 25BREAKING THE SELECTION PLATEAUCastle’s selection experiment-took 15 generations to “break the selection plateau”-recombination through backcrossing to control line allowed for new phenotype with wider stripe to evolve allowed for new phenotype with wider stripe to evolve-recombination extends the “limits” of natural selectionB. Maintenance of variation1. Blending inheritance-Fleeming Jenkin (1867)-does not allow for variation among individuals to be maintained2. Environmental variation-most variation was thought to be environmentally induced3. Survival of mutants-mutants were thought to arise so infrequently that their establishment and evolution into new species was impossiblePolygenic inheritance in corolla length in tobacco (Nicotiana longifloria)Nilsson-Ehle--Morphology in wheat kernels due to at least 10 segregating factorsMore than 59,000 possible phenotypes!Continuous variation results from the inheritance of discrete genesC. Natural Selection couldn’t explain speciation1. Relationship of divergence with speciation?-No mechanisms that promote speciation were known, such as reproductive isolation-Adaptive divergence can result in reproductive isolation between species-This is not always the case. For example with the mice, the white mice live longer and the female mice prefer the mice that are the same color as them.Early-season flowersLate-season flowersRundle et al. 2000Size assortative mating leads to byproduct reproductive isolationBenthic and limnetic three-spine sticklebacks2. Punctuational (not gradual) change observed in fossil record-short period of rapid change followed by long periods of stasis-natural selection should result in gradual, continual change-now know natural selection can result in very rapid evolutionary change (in male guppies, sexual selection is important. Bright color = more sex. Low predationHigh predationMerger of Darwin and MendelII. The Contributions of MendelA. Mendel solved the heritability problem1. Particulate inheritance of discrete traits2. Independent assortment and segregation of alleles produce variation-not all variation is dependent solely on mutationAaB. Problems not solved by Mendel1. Inheritance for continuous traits-Mendel’s laws were based on discrete variation-much variation in natural populations is continuous-thought that environment, not heredity controlled expression of continuous variation(Boag, 1983).Continuous traits can have high heritabilities.Merger of Darwin and MendelIII. The Modern Synthesis (1932-1953)A. The Men of the Evolutionary Synthesis1. Population geneticsR. A. Fisher, J. B. S. Haldane and Sewall Wright-developed mathematical theory of population genetics-demonstrated that mutation is not an alternative to natural selection-mutation is the raw material upon which natural selection and other forces of evolution actDon’t Need to Know This R. A. Fisher: The genetical theory of natural selection (1930)Sewall Wright: Evolution in Mendelian populations (1931)J. B. S. Haldane: The causes of evolution (1932)2. Mutation and its role in evolutionTheodosius Dobzhansky-worked with Drosophila-showed that natural populations harbor the same mutant phenotypes as laboratory populations-laboratory genetics studies were indeed relevant to evolution in nature-Genetics and the Origin of Species (1937)Synthesis of population genetic theory and data on genetic variation and genetic differences between species.White eyes--w Ebony body--eb3. Evolution of speciesJulian Huxley: The New Systematics (1940) Evolution: The Modern Synthesis (1942)Ernst Mayr: Systematics and the Origin of Species (1942)George Gaylord Simpson: Tempo and Mode in Evolution (1944) and The Major Features of Evolution (1953)G. Ledyard Stebbins: Variation and Evolution in Plants (1950)Bernhard Rensch: Evolution Above the Species Level (1959)B. The Impact of the Modern Synthesis1. Integration of genetics and Darwinian evolutionary theory-Evolution results from small genetic changes that are acted upon by natural selection. 2. Processes operating within species account for the major, long term features of evolution-micro evolutionary forces are responsible for macro evolutionary change (origin of species)- Anagenesis leads to cladogeneisisCommon ancestorSpeciationExtinctionAnagenesisStasisCladogenesisSpecies ASpecies B Species C Species DCommon AncestorMerger of Darwin and MendelIV. Darwin’s Theory and Modern GeneticsA. Restating Darwin’s Postulates1. Individuals within species are variable.-Due to mutation creating new alleles.-Recombination shuffling existing alleles into new combinations2. Certain of these variants are passed on to offspring.-alleles are passed on unchanged form parents to offspring.3. In every generation, more offspring are produced than can survive.4. Differential survival and reproduction among individuals exists.-individuals who contribute more offspring to the next generation are those with alleles or allelic combinations that produce traits that are best adapted for the particular environmental features encountered. - those alleles will increase in frequency in the next generationB. Evolution is a genetic process1. Evolutionary change is the change in allele frequencies from one generation to the next in a biological population.2. Evolutionary change occurs by means of natural selection when alleles associated with higher fitness increase in frequency from one generation to the next.Video by Ken Miller •The anti evolution movement is thriving. •Evolution is everywhere, even in our blood. •Because evolution is in our