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Evolution Exam 3Patterns of Character Evolution p.78-833.3 The evolution of Flower Color in an Experimental Snapdragon Population- Establish if natural selection of bumblebees could influence the evolution of a floral trait controlled by alleles of a single gene o Postulate 1: There is a variation among Individuals o Postulate 2: Some of the variation is Heritableo Postulate 3: Do Individuals vary in their Success at Surviving or Reproducing?o Postulate 4: Is reproduction nonrandom?o As a result of all of these postulates, the result was the population evolved. As long as the two first postulates hold true. 3.4 The Evolution of Beak Shape in Galapagos Finches- The deepest split on the tree separates two lineages of warbler finches that still recognize each other as potential mates and are thus classified as belonging to a single species. - Theory of Evolution by Natural Selection Daphne Major’s size and location make it a perfect natural laboratory Population is small and there is little migrationo Postulate 1: Is the Finch Population Variable? Variation in beak deptho Postulate 2: Is Some of the Variation among Individuals Heritable? Individual finches could vary in beak depth because the environments they haveexperienced are different or because their genotypes are different, or both.  Heritability of a trait is defined as the proportion of the variation observed in a population that is due to variation in genes- Therefore, heritability varies between 0 and 1.  In finches, the beak depths of parents and offspring are similar. This observationsuggests that some alleles tend to produce shallow beaks, while other alleles tend to produce deeper beaks. [A substantial fraction of the variation in beak size is due to variation in genotype]p.267-290- Inbreeding that is less extreme than selfing produces the same effect as selfing- it increases the proportion of homozygotes- but at a slower rate- Coefficient of inbreeding (F) – the probability that the two alleles in an individual are identical bydescento Inbreeding Depression- exposure of deleterious alleles to selection May lead to reduced fitness if it generates offspring homozygous for deleteriousalleles Inbreeding effects are often easiest to detect when plants undergo some sot of environmental stress Inbreeding effects are much more likely to show up later in the life cycle o Nonrandom mating does not, by itself, alter allele frequencies. It is not a mechanism of evolution. Nonrandom mating does, however, alter the frequencies of genotypes. It can thereby change the distribution of phenotypes in a population and alter the pattern of natural selection and the evolution of the population Inbreeding increases the frequency of homozygotes and decreases the frequency of heterozygotes- 7.5 Conservation Genetics of the Illinois Greater Prairie Chickeno Destruction of prairie directly reduced the size of the bird’s population and also fragmented the population that remained Small populations with little or no gene flow are precisely the setting in which genetic drift is most powerful Genetic drift results in random fixation and declining heterozygosity - A reduction in fitness due to genetic drift is reminiscent of inbreeding depression Inbreeding depression in remnant populations of greater prairie chickens was caused by a loss of allelic diversity under genetic drift  Migration, in the form of birds transported by biologists appears to be restoring genetic diversity to remnant populations and alleviating inbreeding depression - Chapter 8- Evolution at Multiple Loci: Linkage and Sexo Evolution at Two Loci: Linkage Equilibrium and Linkage Disequilibrium The multilocus genotype of a chromosome or gamete is sometimes referred to as its haplotype- A pair of populations can have identical allele frequencies but different chromosome frequencies o Two Loci in a population are in linkage equilibrium when the genotype of a chromosomeat one locus is independent of its genotype at the other locus (knowing the genotype of the chromosome at one locus is of no use in predicting the genotype at the other) Under HW, chromosome frequencies remain unchanged from one generation to the next if the loci are in linkage equilibriumo Two loci are in linkage disequilibrium when there is a nonrandom association between achromosomes genotype at one locus and its genotype at the other locus  Each generation, the chromosome frequencies move closer to linkage equilibrium if the loci are in linkage disequilibrium  Three mechanisms create linkage disequilibrium in a random mating population- Selection on multilocus genotypes- Genetic drift- Population admixture  Genetic recombination eliminates linkage disequilibriump. 384-392- Tradeoffs and Constraints o Female Flower Size in a Begonia: A tradeoff  Inflorescences with more flowers may be favored by selection for two reasons:- Bees may be more attracted to inflorescences with more flowers- More female flowers mean greater potential seed production o Host Shifts in an Herbivorous Beetle: Constrained by Lack of Genetic Variation Genetic variation is the raw material for evolution by natural selection Chapter 11: Sexual Selection- 11.1 Sexual Dimorphism and Sex Sexual Dimorphism- the difference between the males and females of a species Differential reproductive success due to variation among individuals in success at getting mates is called sexual selection o Asymmetries in Sexual Reproduction Parental investment- energy and time expending both in constructing an offspring and in caring for it - Parental investment is measured in fitness. It increases the reproductivesuccess of the offspring receiving it. It decreases the reproductive success that the investing parent may achieve in the future by way of additional offspring o In more than 90% of mammal species, females provide substantial parental care and males provide little or none  The key to explaining sexual dimorphism is in recognizing that sexual reproduction imposes different selection pressures on females versus males o When one parent invests more than the other in each offspring, the reproductive success of the heavily investing parent is often limited by time and resources. In contrast, the reproductive success of the lightly investing parent is limited by number of mates. o Asymmetric Limits on Reproductive Success in Newts and Pipefish NEWTS: Sexual selection is a more

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FSU PCB 4674 - Evolution Exam 3

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