In some species of beetles, resistance to particular pesticides is a dominant trait. To measure selection on populations after exposure to pesticide, you first establish a population consisting of a mix of resistant and non-resistant individuals and let beetles interbreed freely until you have a very large population of many thousands of beetles. Your initial population meets all of the assumptions of Hardy-Weinberg equilibrium.
After some time, you start your experiment. Before exposing the population to pesticide, you are able to determine that the frequency of the resistance allele in the sample is 0.08.
a) You take a sample of 500 beetles from your large population of freely interbreeding beetles. How many of these beetles do you expect to be resistant to pesticide?
b) You apply pesticide to your original population. In the next generation (Generation 2), you take another sample. You find that the frequency of the resistant allele is 0.34. Based on the change in allele frequency between generations, what is the selection coefficient on pesticide resistance in this population?
c) You raise your beetles for one more generation (i.e., to Generation 3). Starting with your allele frequencies from Generation 2 and assuming that the selection coefficient on pesticide resistance remains the same as what you calculated in (b), what is mean fitness of the population in Generation 2?
d) What are your expected frequencies of the resistant and non-resistant alleles in Generation 3?