Lecture outlines Part 1 Evolution Evolution lecture 1 Pre Darwinian thought APre Darwinian thought i Natural theology Creationism species FIXED ii Linnaeus iii Catastrophism Cuvier and the search for Mastodon iv Gradualism and uniformitarianism Hutton Lyell v Age of the earth Usher and Kelvin vi Evolution at last Lamarck Use and disuse Inheritance of acquired characteristics vii Erasmus Darwin B Darwin s evidence and influences Evidence Ricness of tropical forests Fossils Oceanic islands and Geographic distributions Influences Lyell s principles of Geology Malthus Essays on the principles of populations Artificial selection and Observations during voyage of Beagle see above Evolution lecture 2 Darwin and the genetic basis of evolution ADarwin s theory What it said i Descent with modification ii Natural selection is the mechanism of change Remember though i Individuals do not evolve populations do ii Natural selection can only amplify HERITABLE variation iii Not all variation is heritable much is environmental Problems in Darwin s day i Blending theory of inheritance would dilute variability ii How can selection recognize such small differences iii Is the earth old enough More evidence Artificial selection Systematics Biogeography Comparative anatomy Comparative embryology Fossils and now Molecular biology What is Evolution Make sure you understand this When people say they don t believe in Evolution they are probably using a different definition Darwin presented overwhelming evidence for evolution having occurred and proposed a specific theory natural selection to explain the mechanism of evolution B Mendellian genetics terms to remember character true breeding trait F1 F2 homozygous heterozygous genotype phenotype monohybrid cross dihybrid cross testcross i ii iii Mendel s law of segregation using modern terminology Allele pairs segregate during gamete formation meiosis and the paired condition is restored by the random fusion of gametes at fertilization Mendel s law of independent assortment using modern terminology Each allele pair segregates independently of other gene pairs during gamete formation Mendelian genetics involve the application of these two simple laws and two basic laws of probability Rule of multiplication the probability that independent events will occur simultaneously is the product of their individual probabilities Rule of addition the probability that an event can occur in two or more independent ways is the sum of the separate probabilities of the different ways Evolution lecture 3 Population genetics ABeyond Mendellian genetics i Incomplete dominance dominant phenotype is not fully expressed in the heterozygote ii Codominance full expression of both alleles in the heterozygote iii Multiple alleles each individual can posses only two alleles but there may be many in the population iv Pleiotropic single genes may have many effects and polygenic character determined by many segregating loci traits v Epistasis one gene may modify the expression of another vi Environmental effects gene expression may be affected by the environment vii Linked genes genes on the same chromosome will not assort independently viii Recombination but recombination may sometimes separate even closely linked genes ix Sex linked genes genes on the X but not the Y chromosome John Latto 6 21 07 B Genetic pedigrees i Autosomal dominant genetic disorders ii Autosomal recessive disorders iii Recessive X linked genetic disorders Make sure you understand the simple basics of Mendelian genetics We can use these simple rules with the rules of probability to answer surprisingly complex questions Try answering the questions at the end of Chapter 14 in Campbell Every year people ask me about question 11 6th or 9 7th It isn t a trick question but you do have to use ALL the information you have been given Terminology review make sure you know the following because we ll be using them Gene Allele Locus Homozygous Heterozygous Dominant Recessive C Individuals vs populations i Lifespan one generation vs many generations ii Genetic characteristics genotype vs gene pool iii Evolutionary characteristics no change vs change D Hardy Weinberg principle i Gene frequencies will remain unchanged under certain conditions an ideal population Large population Isolated population No mutations Random mating No natural selection ii If p is the proportion of allele A and q is the proportion of allele a thus p q 1 then after 1 generation of random mating in an ideal population the genotypes will attain and remain at the following frequencies Genotype Frequency AA p2 Aa 2pq aa q2 Evolution lecture 4 Microevolution ASignificance of Hardy Weinberg principle i Gene frequencies DO change over time this is known as MICROEVOLUTION ii Without the H W principle we wouldn t know how to detect this change the magnitude of the change the direction of the change how to begin looking for a cause for the change iii H W principle tells us what happens in the absence of change so we can then detect and measure that change much as Newton s first law of motion does for moving bodies B Microevolution when Hardy Weinberg conditions do not apply i Genetic drift Founder effect and genetic bottlenecks Conservation implications ii Gene flow migration Individuals may move between populations or gametes may move e g pollen iii Mutations Mutations are the source of genetic variation the raw material for evolutionary change But mutation alone does not cause significant changes in allele frequencies iv Non random mating note non random mating will change genotype frequencies but not allele frequencies Inbreeding and inbreeding depression costs seen in the lengths species go to to avoid inbreeding Conservation implications again Assortative mating v Natural selection differential reproductive success How much variation is there in natural populations Two theories in the 1940 s and 1950 s How is variability maintained Diploidy and balanced polymorphisms What can maintain a balanced polymorphism Heterozygote advantage Frequency dependent selection Patchy environment John Latto 6 21 07
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