Types of Selection

 There are various types of selection occurring throughout nature. One type is called balancing selection. In this type of selection, you would observe multiple alleles being maintained in a population due to natural selection. This often leads to the heterozygote being the most advantageous in the population. An example of this is shown with malaria and sickle cell anemia. The fitness of an individual with Aa is higher than the fitness of having aa or AA. This leads to both alleles to stay in the population.

Incomplete dominance is a type of selection where both alleles in a gene are expressed. This means that neither trait is dominant or recessive. An example of this would be the crossing of a red flower and a white flower. In incomplete dominance, the offspring of these two flowers would exhibit a blending of both parent's phenotype exhibiting a phenotype that neither parent has. In this case, the blending of red and white led to a pink flower.

In co-dominance, both alleles of the parents are expressed together in the offspring. If we use a the red and white flower example again this would lead to the offspring would exhibit flowers with red and white patches on them. In this type of selection, both phenotypes of the parents are seen in the offspring

To demonstrate stabilizing, directional, and disruptive selection I chose to use the media I am using for my final project (a monopoly board). To summarize my illustration.....

In directional selection, the one extreme is selected or favored. This leads to a shift in allele frequencies toward the direction of that extreme

 

In stabilizing selection,  the average is selected for and the allele frequency stabilizes on that particular average trait

 

In disruptive selection, individuals with either extreme value is selected for over the average. This leads to a shift in frequency toward both of those extremes