Natural selection at a single genetic locus with two alternate alleles can be modeled for particular situations if we know relative fitnesses for each genotype and assume that they either remain constant or (in frequency dependent selection) that changes in fitness depend only on the frequency of different phenotypes. Genetic drift, evolution that occurs as allele frequencies change randomly from generation to generation, can also be modeled relatively easily if we assume population size stays constant and that the genotypes we are studying do not differ in their effects on fitness. In this exercise, once you are familiar with these general models, you will run programs to determine the possible outcomes of natural selection and genetic drift, over many generations. The program will print a list of the allele frequencies of each of two alternate alleles over the specified number of generations. If you are taking Biology 391 (Organic Evolution) at UT Martin, you will be assigned to use these numbers to make graphs of specific situations so that you can compare the outcome of natural selection in different situations.
To model natural selection or genetic drift, choose one of the species listed below. After reading about it, determine whether it is evolving through natural selection or genetic drift. Use the information you are given, and enter it into the appropriate modeling program (either the natural selection program or the genetic drift program.) The computer will calculate the allele frequency for each generation over a number of generations. Based on these results, you will determine what is expected over time for different situations of natural selection and genetic drift.
Note that the species described are real, and that the situations are based on real situations, but that all have been simplified or modified to some extent to make them fit the models being use, or to better illustrate the goals of this assignment. Thus, the information given for these species should NOT be taken as factual information!