Throughout the process of this lab many mechanisms of evolution were observable, most prominently the mechanism of natural selection. In order for evolution by natural selection to occur three requirements must be met. The first is that individuals in the population must vary in trait that is being considered. Also the trait be considered must also be heritable, meaning it must be able to be passed down from generation to generation through germline cells. Lastly there must a selection differential, which simply means that the trait being considered must either increase or decrease the likelihood of the organism to survive and reproduce. This idea of evolution through natural selection was discussed throughout the SimUText Lab and was displayed during the Flat Periwinkle snail activity. In the activity the trait of Periwinkle shell thickness was shown to be variable, heritable and provided a selection differential, in the case of this trait a thicker shell resulted in a greater likelihood to survive and reproduce in an environment that contained predation by crabs. This trend of thicker shells leading to a higher likelihood of survival and reproduction in Flat Periwinkle populations was the driving force behind the constructed hypothesis for the effects of crab predation on the Dogwinkle snail population. The Dogwinkle snail species is the species under observation in the experiment, the Dogwinkle species exists in two distinct factions, an Eastern and a Western. In the Eastern population there is a predation pressure due to the presence of Rock Crabs and the average shell thickness of the Eastern population is thicker than the Western population in which there is no Rock Crabs present. With all of this information under consideration the hypothesis reads as follows, if there is predation by crabs present and the trait of shell thickness is being observed, then evolution by natural selection will occur and a shift to a larger average shell thickness in the experimental tanks containing the Dogwinkle snails can be expected.
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