Discussion: Natural Selection and Overtime Shell Thickness Essay

Submitted By princessmaddie4525
Words: 420
Pages: 2

Discussion
On the rocky shores of New England, lives the Flat Periwinkle, the species observed in this experiment. In order to determine the effect of natural selection, shell thickness was recorded throughout various generations of the same population. An array of characteristics that influence the thickness of an individual’s shell were targeted and the effects of each were observed; variation, inheritance, and mutation.
Overall, the observed results matched what was expected. When left to the process of natural selection, snails with thinner shells were less likely to survive than those with thicker shells. When a specific factor was added or removed, the process of selection became harder to predict, meaning that the normal processes of evolution were not observed.
Overtime shell thickness trended towards thicker diameters as generations continued to be exposed to predation through natural selection. Without the exposure to predators such as the European Green Crab, the evolution of shell thickness would have remained relatively stagnant due to the decreased need for survival. As shown in in the first set of histograms, shell thickness had a fairly uniform distribution before predation occurred, five being the average thickness. As further observations were made, the data showed a major increase in the overall thickness of shells in the populations.
In order for evolution to occur through the process of natural selection there are a few things that must be present: variation, inheritance, selection, and mutation. One population began with an entire generation of snails with identical shell thicknesses. Without the presence of genetic variation, the process of evolution did not occur. The absence of genes permitting thicker…