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U of A ANTH 1013 - Evolutionary Synthesis: Microevolution

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ANTH 1013 1st Edition Lecture 6Outline of Last Lecture I. DNAII. ProteinsIII. Protein SynthesisIV. Coding vs. Noncoding DNA SequencesV. MutationsOutline of Current Lecture I. The Evolutionary SynthesisII. How does evolution occur?III. MutationIV. Natural selectionV. Gene flowVI. Genetic drifVII. What if population isn’t evolving?Current LectureI. The Evolutionary Synthesisi. In the early 1900’s, evolutionary biologists merged Darwin and Mendel’s ideas to create a cohesive body of evolutionary theory known as: the NeoDarwinian Synthesis, or the Evolutionary Synthesis or Modern Evolutionary Synthesisa. The focus of this synthesis is on understanding how the frequency of alleles change over timeii. Focus on how alleles change in frequency over timea. When we consider the gene pool of a population, evolution can be defined as: a change in allele frequency over time1. Individuals do not evolve, populations or species doiii. Alleles in populationsa. How many alleles are in this population?1. 2 alleles per individual x 100 individual = 200b. Allele frequency = percentage of each allele in a populationiv. Evolution is a phenomenon of the gene poola. Gene pool: the collection of alleles present in a populationb. Evolution: a change in allele frequency over timeII. How does evolution occur?i. There are 4 central mechanisms that contribute to changing allele frequencies over time:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Mutationb. Natural selectionc. Gene flowd. Genetic drifIII. Mutationi. The creation of new allelesa. Mutations create a variation within the gene pool, making long-term evolutionary change possibleii. Mutations create new alleles, making new phenomena possiblea. Mutation is the only evolutionary mechanism that introduces NEW variation into the gene poolb. Mutations occur RANDOMLYc. Mutations are important because they are the ultimate source of all heritable variationiii. Critical role in evolutionary changea. The fate of new alleles lies with natural selection, genetic drif, and gene flowb. Some mutations may lead to an increase in fitness1. Sickle Cell Anemiac. While some may have low fitness1. Phenylktonuria (PKU)iv. Mutation: sickle cell allelea. Single change in a base is what causes itb. Having just one sickle cell allele is advantageous in areas with malaria1. Able to fight off malaria more effectivelyv. Mutation: PKU allelea. Condition where body cannot break down phenlalanine. If unchecked phenylalnine stays in blood stream and inhibits normal brean growthIV. Natural Selectioni. Process by which populations become better adapted to their environment. Differential survival and successa. Based on the fitness of an individualb. Average ability of individuals of a given genotype to reproduceii. There are several categories of natural selection:a. Directional selection – selection at one end of the range of phenotypesb. Stabilizing selection – selection for the average phenotypec. Sexual selection – selection arising as a result of preference by one sex for certain characteristics of the other sexiii. Galapagos finches demonstrate directional selectiona. Study observed that the birds that survived had deeper bills and were larger in body sizeiv. Gene pool – the collection of alleles present in a populationa. The frequency of the alleles contributing to the smallest beaks decreased in frequency, while the alleles contributing to large beaks increased in frequencyv. Directional selection: selection at one end of the range of phenotypesa. Over time the average beak depth is getting larger in response to directional selectionvi. Stabilizing selection: selection for the average phenotypea. Over time, the extreme values have been eliminated, that is, the mean has not changed but the range decreased1. Staturevii. Sexual selectiona. Selection arising as a result of preference by one sex for certain characteristics of the other sex1. Male facial hair2. Female breasts3. Increased penis sizeV. Gene Flowi. The introduction of alleles from one population to another due to migration and matinga. Only occurs among populations within a species, not between speciesVI. Genetic Drifi. Chance changes in allele frequency from one generation to the nexta. High in small populations due to small size of gene poolii. Genetic bottlenecka. Reduction in genetic diversity due to dramatic temporary decrease in population sizeiii. Founder effecta. Loss of genetic variation when a new colony is establishedVII. What if population isn’t evolving?i. If evolution is a change in allele frequency over time, what happens if the allele frequencies aren’t changing?a. Then population is said to be in equilibriumb. To be in equilibrium none of the evolutionary mechanisms are operating; otherwise, the allele frequencies would be changingii. Hardy-Weinberg equilibriuma. Populations in equilibrium have special mathematical propertiesb. A 2 allele system:1. Allele frequencies: p + q = 12. P = frequency of dominant allele3. Q = frequency of recessive allelec. Genotype frequencies: p^2 + 2pq + q^2 = 11. These are the genotype frequencies that you expect if no evolutionis occurring2. If no evolution is occurring then the frequencies of p and q will be the same in every generationd. But, for a population to be in equilibrium none of the evolutionary mechanisms are operating; otherwise, the allele frequencies would be changing1. Requirements for equilibriuma. Infinite population size (no genetic drif)b. No mutation – no new alleles are being added to the gene poolc. No gene flow – no exchange of alleles with other populationsd. No natural selection: alleles have equal fitnesse. No assortative mating (mating is random): all male/female matings have an equal probabilitye. Why do we care?1. If gives us a null hypothesis to test, and outlines what to expect if no evolution is occurring2. If the population is not in equilibrium, then the population is evolving3. Demonstrates that evolution occurs easily; no natural population will meet all of these


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