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EVOLUTION Instructor: Patricia Princehouse MW 1230-1:45 pm DeGRACE 312 Attendance Required 217 Rockefeller 440-478-5292 [email protected] BIOL/ANTH/GEOL/HSTY/PHIL 225 Darwin and the Nature of Science Lunar Society Lunar Society The Mount, Shrewsbury Maer Hall Edinburgh “You care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family” -Robt Darwin to 16-year-old Charles Edinburgh Robert Grant Cambridge Voyage of the Beagle Darwin Children Darwin Children Darwin Children Sir Richard Owen Joseph Hooker TH Huxley Charles Lyell Alfred Russel Wallace What is Science? The Scientific Revolution 17th Century Science New systems: Copernican Revolution, Galileo, Descartes, Newton New reliance on experiment – formation of scientific societies witnessing together Separation of science from politics (i.e. religion & government) Renewed interest in arguments for the existence of God, especially the argument from design Science since Newton: Uses only natural explanations (methodological materialism) Prefers reductionist explanations (Ockham’s razor, parsimony) Addresses “How”, rather than “Why” Testable Correctible Extendable The 3-fold Structure of Science Primary Theory (core inference) Secondary Theories (mechanisms) Tertiary Theories (hypotheses/scenarios) The 3-fold Structure of Science Core inference Heliocentrism Descent with modification Mechanisms Copernicus’ concentric spheres Kepler’s laws Newton’s laws Relativity theory String theory Hypotheses /scenarios Halley’s comet Eclipses Orbit of Mercury Red shift Hawking radiation The 3-fold Structure of Science Core inference Heliocentrism Descent with modification Mechanisms Copernicus’ concentric spheres Kepler’s laws Newton’s laws Relativity theory String theory Hypotheses /scenarios Halley’s comet Eclipses Orbit of Mercury Red shift Hawking radiation The 3-fold Structure of Science Core inference Heliocentrism Descent with modification Mechanisms Soft Inheritance Pangenesis Orthogenesis Saltationism Natural Selection Mutation Genetic Drift Gene Flow Genomics Allometry Hypotheses/ scenarios Giraffe’s neck Mammalian ear bones Hardy-Weinberg models DDT resistance Peppered moth Gene families Evo-Devo details Lucy ancestral… Biology Lamarck 1744-1829 -Characteristics acquired in response to the environment during the lifetime of an organism can be passed on to its offspring -Separate lineages spontaneously generate & transmute through progressively higher levels of organization “On the view that species are Charles Darwin only strongly marked and “To my varieties, mind it accords permanent and that better withfirst what we know each species existed as a of thewe laws impressed onis variety, can see why it matter byofthe Creator, that that no line demarcation can the production and be drawn between species, extinction of the past and commonly supposed to have present inhabitants of the been produced by special acts world shouldand have been due of creation, varieties to secondary causes.”to which are acknowledged have been produced by secondary laws.” Charles Darwin “Man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system –with all these exalted powers— Man still bears in his bodily frame the indelible stamp of his lowly origins” “Descended from the apes? My dear, we will hope it is not true. But if it is, let us pray that it may not become generally known.” -Mrs Canon of Worchester, 1859 Poets say science takes away from the beauty of the stars - mere globs of gas atoms. Nothing is 'mere'. I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination - stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern - of which I am a part... What is the pattern or the meaning or the why? It does not do harm to the mystery to know a little more about it. For far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were a man, but if he is an immense spinning sphere of methane and ammonia must be silent? -Richard Feynman “There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” “What the Frenchman did for species, I will do for forms.” -Darwin, 1838 notebook Charles Darwin 1809-1882 Heaven Transformational forfend me from Change Lamarck nonsense of a vs ‘tendency to progression’ Variational C. Darwin Change Natural Selection Superfecundity Small-scale, Copious, Undirected Variation Strong Principle of Heredity PROBLEM: Nature of Variation? Hard inheritance: Soft vs Hard Particulate Blending inheritance inheritance Fleeming Jenkin Nature of Variation Particulate inheritance Pangenesis theory Combined hard & soft inheritance Expanded by DeVries Nature of Variation Rediscovery of Mendel 1900 -Particulate inheritance -Sequestration of germ plasm; August Weismann -Macromutation as the basis for speciation; Hugo DeVries -Small-scale mutation as basis for gradual variation; TH Morgan Nature of Variation How Mendelism solved Darwin’s problem: -Distinction between phenotype & genotype -Discrete units of inheritance Genetic Theory Mendelian Inheritance X F1 A sexually reproducing diploid organism = Mendelian Inheritance X F1 F1 X F1 = F2 = Mendelian Inheritance X AA aa = F1 Aa Aa Aa Aa F1 X F1 = (Aa X Aa =) F2 AA Aa Aa aa Mendelian Inheritance X Homozygous dominant AA aa = Homozygous recessive F1 Heterozygous F1 X F1 = Aa Aa Aa Aa (Aa X Aa =) heterozygote x heterozygote F2 AA 25% Aa Aa 50% aa 25% X Mendelian Inheritance Punnett Square Mother’s alleles A AA aa Father’s alleles A a Aa Aa a Aa Aa Inside the boxes are the genotypes of the offspring X Mendelian Inheritance Punnett Square Mother’s alleles A Aa Aa Father’s alleles a A AA Aa a aA aa Inside the boxes are the genotypes of the offspring X Mendelian Inheritance Punnett Square Mother’s alleles A Aa aa Father’s alleles a a aA aa a aA aa Phenotypes of the offspring: PROBLEM: Nature of Variation? Hard inheritance: 19th C: Blending inheritance Soft vs Hard inheritance vs. Particulate inheritance Fleeming Jenkin Mendelian Inheritance X - Additive Loci = Mendelian Inheritance - Additive Loci = X AA aa Aa Aa Aa Aa Draw a Punnett Square illustrating the genotypes of an F1 x F1 cross Mendelian Inheritance - Additive Loci = X Aa AA Aa Aa Aa aa So, what about genes in populations? Australian Cattle Dogs -Clinic held at the National Specialty show -100 dogs examined by an ophthamologist -49 are found to be affected by Progressive Retinal Atrophy (PRA) blindness -What is the likelihood that unaffected dogs are carriers? -Will the disease disappear from the population? To deal with genes populations, we Cattle Dog in example: startq2with an oversimplified model = affected individuals (49/100 aa) that preserves some important q=? p =? # of non-carriers? factors for us. Hardy-Weinberg Theorem p+q=1 p2 + 2pq + q2 = 1 p = frequency of dominant allele (A) q = frequency of recessive allele (a) Assumptions of the Hardy-Weinberg Principle 1) Mating is random 2) Infinitely large population 3) Closed breeding colony 4) No mutation 5) Equal probability of survival & reproduction fmi Futuyma Significance of the Hardy-Weinberg Principle “Foundation on which almost all of the theory of population genetics of sexually reproducing organisms --which is to say, most of the genetic theory of evolution-- rests.” -Futuyma -In the absence of perturbing factors, allele & genotype frequencies remain constant over generations -Not dependent on past history of the population (first order Markov process) -Ratios often hold in studies of natural populatons -Deviations often demonstrate Natural Selection at work Fisher Haldane Dobzhansky & Morgan Wright Mayr McClintock Natural Selection Superfecundity Small-scale, Copious, Undirected Variation Strong Principle of Heredity Modern Synthesis: 4 Forces of Evolution Natural Selection Genetic Drift Gene Flow Mutation What’s wrong with this picture? The Argument from Design Natural Theology Rev William Paley, 1802 "In crossing a heath, suppose I pitched my foot against a stone and were asked how the stone came to be there, I might possibly answer that for anything I knew to the contrary it had lain there forever; nor would it, perhaps, be very easy to show the absurdity of this answer.” The Argument from Design Natural Theology Rev William Paley, 1802 "But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place, I should hardly think of the answer which I had before given, that for anything I knew the watch might have always been there.” The Argument from Design Natural Theology Rev William Paley, 1802 "Yet why should not this answer serve for the watch as well as for the stone? For this reason, and none other, viz., that when we come to inspect the watch, we perceive what we could not discover in the stone, that its several parts were put together for a purpose." Argument from Design Natural Theology – Rev William Paley, 1802 Paley’s conclusion: “when we come to inspect the watch, we perceive what we could not discover in the stone, that its several parts were put together for a purpose..“ …gets extended to the stone as well… X Mendelian Inheritance Punnett Square Ee You do it: List genotypes of parents & offspring in Punnett Square form & give the phenotypes of each ee Mendelian Inheritance Punnett Square 2 Ee pups You do it: What are the probable genotypes & phenotypes of the parents of this litter? 3 ee pups X Mendelian Inheritance Punnett Square Mother’s alleles A Aa Aa Father’s alleles a A AA Aa a aA aa Inside the boxes are the genotypes of the offspring