Experimenting with Selection
Experimenting with Selection
We going to use out virtual mosquito lab to investigate how natural selection can lead to the rapid emergence of resistance in a population. This time the simulation is going to have one extra parameter, a fitness coefficient for each of the possible genotypes. The fitness coefficient is a value between 0 and 1 which represents the proportion of mosquitoes of this genotype that survive to adulthood.
Experiment 1: The difference between drift and selection.
If every offspring survives until adulthood then we no longer have selection acting on our population. In this case every genotype would have a fitness coefficient of 1. Compare the rate of fixation in a population where selection is acting against that of a population experiencing drift.
Which population reaches fixation quicker?Experiment 2: Exploring the rate of fixation of new alleles
We saw in the last section that new alleles created by mutation can be lost very rapidly if they are subject to genetic drift. What would happen if this new allele conferred a selective advantage on this organism? Start with a frequency of one allele and see how long it lasts with and without a selective advantage.
Experimenting with Selection
Graph of Allele Frequencies
We've already seen that mutation can increase the allelic diversity of a population and that this diversity is subject to random processes. However neither of mutation or drift is sufficient to explain how organisms evolve to adapt to their environment. The missing piece of this puzzle is natural selection, a way to give direction to the random processes of mutation and drift.