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Berkeley BIOLOGY 1B - Lecture outlines

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John Latto 6/21/07 Lecture outlines – Part 1: Evolution Evolution lecture 1 - Pre-Darwinian thought A - Pre-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 A - Darwin’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) 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. ii) Mendel’s law of independent assortment (using modern terminology) Each allele pair segregates independently of other gene pairs during gamete formation iii) 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 A - Beyond 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 chromosomeJohn 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 A - Significance 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


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Berkeley BIOLOGY 1B - Lecture outlines

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