biol2400-evolution-final-exam-practice-short-answer-questions-f2022-ver1-solutions

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Studocu is not sponsored or endorsed by any college or university BIOL2400 Evolution Final Exam practice short answer questions F2022 ver1 Solutions Evolution (University of Guelph) Studocu is not sponsored or endorsed by any college or university BIOL2400 Evolution Final Exam practice short answer questions F2022 ver1 Solutions Evolution (University of Guelph) Downloaded by ibrahim dyub (idyub1729@gmail.com) lOMoARcPSD|20043975

BIOL*2400 Evolution April 13, 2022 Practice Final Exam short answer questions (The final exam will have two short answer questions chosen out of four). Note that emphasis of exam will be on material since Midterm 2 but I have included some practice questions from earlier in the course. Dr. Elizabeth Boulding Short Answer: Briefly answer the following questions in the space provided. Remember that longer answers are not necessarily better and we recommend that you make an outline of your answer on the back of the previous page before starting to write. Please show details of all your calculations and label any figures or tables that you draw. Put your name and student number on all pages even the ones that you do not do. All parts of the question are worth the same amount of the total. **Note, however, that there are lots of tables requested below to help you summarize your notes but many of the Final exam short answer questions will NOT involve making a table. 2) [10 marks] You are studying a population of deer mice Peromyscus maniculus in Algonquin Park. You are interested in whether there is a heritable component to body weight and to running speed for a sprint of 30 metres. You trap wild mice for two generations and estimate that for this population: Table 1. Phenotypic statistics and heritability for a deer mouse population. Trait mean variance h 2 N body weight (g) 30.0 10.7 0.37 a 400 Sprint speed (ms -1 ) 10 4.0 0.61 a 400 a Narrow sense heritability from the slope of a linear regression with the average offspring value as the y value and the average value for their parents as the x value. a) Which trait has the larger phenotypic variance using its original units? b) Calculate which trait has a larger additive genetic variance using its original units. (Assume that the phenotypic variances are similar in the laboratory and in the field and that the trait has the same genetic basis in both environments). Downloaded by ibrahim dyub (idyub1729@gmail.com) lOMoARcPSD|20043975

Recall: h 2 = V A / V P and has no units of measurement. For body weight: From Table: mean body weight = 30 g, phenotypic variance, V P, = 10.7, h 2 = 0.37 Therefore : V A = 3.959 For sprint speed mean sprint speed = 10 ms -1 , V P = 4.0, h 2 = 0.61 Therefore: V A = 2.44 Body weight has a larger additive (=heritable) genetic variance than sprint speed. c) Your summer’s trapping data shows that there was intense selection for decreased body size (S, the selection differential is − 1.271) likely because of changes in predator abundance. Use this estimate of S and the data from the Table 1 above to predict what the mean body size would be after one generation of directional selection. Recall: R = h 2 S. Note that the selection differential, S = −1.271 (It is negative because the mice are getting lighter). After one generation: R = (0.37)(−1.271) R = − 0.47 g per generation Also recall that: 끫 = 끫̅ 끫2 − 끫̅ 끫1 Downloaded by ibrahim dyub (idyub1729@gmail.com) lOMoARcPSD|20043975

Rearranged: 끫̅ 끫2 = 끫 + 끫̅ 끫1 Therefore after one generation new mean weight is predicted to be: 끫̅ 끫2 = − 0.47 + 30.0 끫̅ 끫2 = 29.53 g **Note that to estimate the total response to selection over multiple generations one just keeps doing these calculations for each generation. This assumes that selection differential is constant and that the heritability does not change despite the strong selection. 3) [10 marks] You are responsible for monitoring a non-indigenous species of mollusc-eating fish that has been accidently introduced into the Great Lakes. You have found that each year the average body size of this fish population is becoming larger with a relatively deeper and more heavily muscled head region and more massive teeth. You have also observed that each year the stomachs of the larger fish contain progressively larger and thicker-shelled zebra mussels. a) Suggest a hypothesis based on the breeder’s equation quantitative genetics that explains why and how this fish population might be evolving a larger body size. b) How might the shell thickness of the zebra mussels respond to this increased jaw size by its predator? A reasonable hypothesis is that there is ongoing coevolution between the mollusc-eating fish species and the zebra mussels. Assume that the predator is evolving a larger and deeper jaw so that it can better crush larger and thicker zebra mussels. Its body size is increasing because body size is genetically and phenotypically correlated with jaw size because of pleiotropy (changes in allele frequencies at several loci that affect both traits simultaneously). In response to the greater forces that can be generated by the larger head and jaw that is evolving in the mollusc-eating fish population, there is selection on the zebra mussel population to grow quickly to a large size so that they become too large to fit in their predator’s mouth and selection for them to develop a thicker shell so that the fish’s jaw is not strong enough to crush them. The rate at which the zebra mussel evolves a thicker shell would be predicted to be a product of the selection differential on shell thickness multiplied by the heritability of shell mass. Specifically: R = h 2 S Downloaded by ibrahim dyub (idyub1729@gmail.com) lOMoARcPSD|20043975

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