ps1-06 - Biological Sciences 1130 Evolution. Spring 2006...

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Unformatted text preview: Biological Sciences 1130 Evolution. Spring 2006 Problem Set #1 This problem set is worth 25 points toward your final grade in BS1130. It is due January 26, 2006 at the beginning of class. Answer sheets will be handed out at that time so no late assignments will be accepted. If you do not turn in a problem set, you will receive 0/25 for the assignment. As a general rule when answering questions for this class, clearly write out 1) any assumptions you make, 2) any formulae you use 3) and define all the variables that you use. While you should feel free to discuss the general aspects of these problems with your fellow students, the solutions and interpretations are to be entirely your own, and given the nature of the problems any deviations from independent work will be obvious. 1. (10 pts.) It is summer and you are taking a class at the Pymatuning Lab of Ecology. As you meander onto the volleyball court, you find 545 long horned beetles that were flooded out of their underground homes by a torrential storm. You collect all the beetles, take them to the dining hall and sort them into groups on the basis of color. You find that 210 are grey, 130 are black and 215 are brown. You take them to your room and realize that 220 of them are not alive. Upon close inspection, you see that among the individuals in your sample 125 black beetles are alive, 100 with brown are alive, and 100 grey are alive! You consult the literature and discover that this color polymorphism is controlled at a single color locus with two alleles. The beetle color depends on the number of copies of the color alleles [C] an individual has (0 color alleles results in an gray beetle, 1 copy of the C allele results in a brown beetle and 2 copies of the C allele result in a black beetle). a. Assuming your collection accurately reflects the distribution of phenotypes in the beetle population living in nature, calculate the genotype and allele frequencies before selection. b. Was the population in Hardy-Weinberg equilibrium before selection? Explain. (Statistical support not necessary). c. What are the absolute fitness values (survivorship), the relative fitness values and the selection coefficients for each of the 3 genotypes? d. What is the change in allele frequency for this episode of mortality selection? What are the new allele frequencies after the episode of mortality selection? 2. (5 pts) A wooly mammoth was discovered frozen in the ice of the Arctic and sampled by microbiologists to determine if there is a similarity between the intestinal bacteria of the wooly mammoth and present day elephants. The sample contained a type of bacteria new to microbiology and scientists were able to culture the bacteria in the lab. After a few months of testing, this bacterial strain was found to contain a new functional allele in a common bacterial metabolic pathway that allows the bacteria to metabolize both glucose and maltose. This mutant allele arises at a rate of (1 X 10-3) and it is lost at a rate of 3.5 x 10-4. Assuming that mutation is the only evolutionary force acting in these cultures, and that the bacterial culture has had sufficient time to reached equilibrium allele frequencies, what is the expected allele frequency of the new “eats glucose and maltose” egm allele? 3. (5pts) Explain each of the variables in this equation and the possible range of values for each. ˆ q= µ s Thinking qualitatively: If you observe a high value of µ , and the value of s is low, what would you speculate that the q allele effects are likely to be? (e.g. highly beneficial, mildly deleterious, ˆ etc.) What would you predict the value of q to be? (e.g. q goes to fixation, q is maintained at € relatively low frequency, etc.). € € 4. (5pts) For the following graph of a phenotypic distribution, draw a fitness function and the new phenotypic distribution that you would expect and describe the change in the mean and variance of the phenotypic distribution if selection on the trait was: Disruptive Positive directional variance Stabilizing Mean Negative directional ...
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This note was uploaded on 01/08/2009 for the course BIOSC 1130 taught by Professor Kalisz during the Spring '08 term at Pittsburgh.

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