Prompt 8

As mentioned in the prompt, when one thinks of selection, often they think of it as mechanism that filters out genetic variation. The genotypes with great amounts of fitness are able to move on while those that lack fitness often get kicked out of the running. As a result, we would think that diversity would be eliminated rather than stable or increased. However, genetic variation is allowed to continue by the other mechanisms that are play that are continually keeping variation in the genetic pool. 

Genetic drift can result in fixation, but it also can result in the the maintenance of a mutation. In a way, it is almost is a counter to selection by introducing random interferences that allow a certain allele to be kept. It is more of wildcard when it comes to genetic variation.

Additionally, there are the factors of mutation. While mutation is not the most reliable mechanism for preventing the erosion of genetic variation due to selection picking off the less fit variations, mutations are still able to introduce alleles into the gene pool. Of course, we did the mutation calculations and saw that they are not the most effective mechanism.

Furthermore, there is the factor of the heterozygosity. As we saw in one of the R exercises, deleterious alleles that are recessive will often stick around for awhile due to the heterozygote keeping it around. While homozygotes will be at risk, the heterozygote can keep the variation in the population by keeping alleles "stored," allowing the population to maintain variation, even if the environment typically does not favor that genetic combination. 

In continual reference to our R exercises, when we were looking at negative frequency dependent selection, we it is helpful in helpful in maintaining diversity. We saw that oscillating wave that the more the fitness of a phenotype or genotype decreases, the more common it becomes. As a result, the selection balances out, so selection is able to increase the genetic variation. 

As for quantitative genetics, often we can see that it can act in a way to preserve genetic variation as well. Quantitative genetics produces populations that fit a standard normal curve, which favors the heterozygotes in a population but allows there for those that fall from the average to still make it into the normal curve since there is typically not an extreme skew toward each population.