1 BIO171 Discussion Reasoning about Evolution This discussion supports the following objectives aligned with lecture 20 21 and 22 1 Describe the effects of positive negative and balancing selection on allele frequencies in a population 2 Reason how changes in allele frequencies affect genotype and phenotype frequencies 3 Recognize examples of directional selection given a population with a discrete set of traits caused by one gene with 2 alleles 4 Explain why stabilizing selection describes a change in the distribution of phenotypes when we are considering a continuous trait 5 Use knowledge of relative fitness to analyze the types of selection happening in a population 6 Use evolutionary processes to describe the change in the genetic make up of population s given a scenario 7 Calculate relative fitness given information about reproductive success 8 Interpret relative fitness in the context of differing or changing environments Prepare yourself for discussion Do Practice Question Set 20 1 4 It would be helpful to do the entire PQ Set but 1 4 are required Lecture 19 is pre requisite to lectures 20 22 Be sure to master the lecture 19 learning objectives the portions about Darwin and evolution Do the preparation for the Lecture Canvas Quiz due on April 2 o This week s discussion focuses on Lectures 20 21 and 22 Please write out answers to the guiding questions and use these notes during discussion Illnesses and other circumstances The guidelines for what to do in an emergency or extraordinary circumstance or illness are here https umich instructure com courses 575097 pages discussion illness and other circumstances 2 Discussion Preparation Activity Graded These questions will be on your Discussion Canvas Page Generally reasonable answers will receive full credit and this is graded for completion However if the question asks you to repeat something directly from course material you must do that accurately Also you must answer the question as asked For example if the question asks for an equation and you give 2 words then you will not receive credit There is no partial credit This is worth 1 point Question 1 Please upload your WORK for Practice Question Set 20 1 4 in PDF format For free response questions you must write out your ideas If it is easier you may INSERT images use jpg format We must be able to read your work to offer credit Question 2 In BIO171 we use a very precise definition of the evolution of populations What is that definition Achange in Allele Frequency within a population over time the allele is expected to decrease alsothe allele confers a fitness disadvantage Question 3 If positive selection is acting on an allele what happens to the allele frequency over time What happens if negative selection is acting on an allele Ifpositive selection occurs the frequency of the allele in the pop is expected to increase over time also the allele confers a fitness advantage If negative the freeof Question 4 Which of the following tends to reduce the diversity of a population Explain your reasoning Choices balancing selection and stabilizing selection Stabilizing selection tends toreduce the diversity pop because itfavors the intermediate phenotype over the extreme phenotypes Therefore stabilizing reduces genetic diversity of a pop by eliminating the rare alleles associated with the extremes 3 Main Exercise Worksheet 1 What are the possible mechanisms that could cause the evolution of a population Please list all possible evolutionary mechanisms Genetic Drift Gene Flow Mutation Natural sexual selection 2 Consider a group of researchers focusing on a gene E How would they know if the population was evolving with respect to the E gene Hint What changes when the population evolves Frequency ofthe Allele would change Imagine a very large population of butterflies living on an island that is very isolated from other butterfly populations on an island called Butterfly Island The wings of this species have one large eyespot each At year 1 all the butterflies had blue eyespots on their wings and this has been the situation for 1000 butterfly generations This is what an EYESPOT looks like In year 2 an extremely unusual wind pattern generated by a super storm blew a group of butterflies of the same species from a distant mainland population to Butterfly Island This migrant group had white eyespots The migrants successfully mated with the resident butterflies of Butterfly Island Fortuitously researchers know a lot about butterfly genetics Assume that eyespot color is determined by a single gene E with 2 alleles EB and EW When the migrants and the resident butterflies mated on Butterfly Island their 1st generation offspring all had light blue eyespots 1 3 When the super storm blew the white eyespot butterflies to the island and the migrants mated with the residents was this evolution If so what process was causing the evolution name it If not explain why not using the definition of evolution Gene Flau 1 Image credit Didier Descouens http en wikipedia org wiki File Caligo martia ventre jpg 4 Some researchers noticed this new light blue phenotype and wondered if there was a difference in fitness among the phenotypes 4 What type of dominance do the EB and EW alleles have Incomplete Dominance 5 The researchers think that either balancing selection or directional selection is affecting eyespot coloration They are not sure which is occurring They watch the butterflies for 15 butterfly generations Assume that the frequency of EB begins at 0 99 and the frequency of EW begins at 0 01 a If selection occurs and favors the white eyespot phenotype what do you predict will happen to the frequency of the EB and EW alleles Why What kind of selection is this i After many many generations what will the frequencies of the phenotypes be Idecreases Iincreases Directional if this type of selection is happening EN 99 EB 01 ii What terms describe the selection on the EB and EW alleles Assume the selection scenario described in this question Directional Selection Positive b If selection due to heterozygote advantage happens what will happen to the frequency of the EB and EW alleles Why What kind of selection is this Balancing both will be maintained because heterozygotes have higher i After many many generations how many phenotypes will exist in the Itness population if this type of selection due to heterozygote advantage has acted on the population Why 3 I white blue or light blue Use this information to help you