John Henry
2/11/11
Experimental Biology II
Evolution and the Flat Periwinkle: An Assessment
Abstract
	Without the process of evolution, life would not exist today as we know it. The Earth would be uninhabitable and bacteria never would have split off into the two additional domains of life—Archaea and Eukarya. Over the eons, the environment changed for the better, with multi-cellular Eukaryotes beginning to inhabit the planet and the slow process of aquatic organisms transitioning into land plants. The Eukarya domain eventually expanded into the Kingdom Animalia, a diverse group of multi-cellular organisms that includes the two organisms that were analyzed in the first lab: the Flat Periwinkle and the European Green Crab.
The process of evolution is a process that weeds out the weaker individuals in population by naturally selecting the most fit to survive. As time flowed, the lesser desirable traits were eliminated, and assorted populations were forced into evolving. In the case of the Flat Periwinkles and the European Green Crabs, the less desirable traits (poor shell thickness) resulted in the predation of those Flat Periwinkles. The lucky few survivors with thicker shells lived long enough to reproduce and as a result began the process of evolution.
	SimUText was used quite primarily in this experiment, providing a concise area in which an experiment that would normally be very difficult to organize could be replicated with ease. In essence, SimUText allows the user to create hypotheses by playing around with a gene pool and testing those theories. For the purposes of the lab experiment, three conditions of evolution were tested on the Periwinkles: whether or not shell thickness is variable, heritable, or if survival is selective. Additionally, the element of gene mutation was a key point of this week’s lab experiment. Using the postulate set forth by Darwin, evolution will occur if heritable variation results in differential success in survival and reproduction. The conditions in which we examined the hypothetical population of periwinkles mostly leaned towards the snail population not evolving, unfortunately.
This lab experiment reproduced Robin Seeley’s results on whether or not evolution occurred on the population that became subjected to feeding on by the immigrating European Green Crabs in the late 19th century.  Seeley examined two records of periwinkle shells collected from 1982-1984 and from 1871, the year before European Green Crabs arrived on the North American coasts.
Table 1. Shells Collected in 1871, Before European Green Crabs Arrived
5	8	1	9	4	8	8	8	11	2
9	8	7	8	5	8	8	12	9	10

Table 2. Shells Collected in 1982-1984, Eighty Years After European Green Crabs Arrived
14	11	12	14	9	11	12	13	14	10
14	10	14	12	13	10	15	13	14	15

	Before the European Green Crabs had arrived, the Flat Periwinkles were relatively thin shelled. However, with the arrival of a new predator, the thicker shelled periwinkles were innately fit to survive as their shells were much tougher to crack. As the weaker periwinkles continued to be preyed upon, the stronger—or thicker shelled periwinkles—were the only ones to be able to reproduce. In this way the periwinkles were able to undergo evolution by inheriting much more desirable traits to survive. As evidenced between Tables 1 (before the European crab invasion) and Table 2 (after the European crab invasion) it’s been made extremely clear that the crabs spurred along evolution in the indigenous periwinkle population.
 	As the lab experiment proved, certain conditions must be met in order to have evolution occur. For instance, in Table 1, there is quite a difference in the shell thicknesses of the periwinkle population. One of the experiments conducted was the assumption that the entire population of periwinkles were of the same shell thickness, thus making heritable variation impossible. With the exclusion of mutation, the periwinkles would be doomed to a cycle of life and death by crabs, as the possibility of offspring inheriting a thicker shell allele is impossible. In this way, shell thickness must be a heritable trait, the population must also vary in its shell thicknesses, and selection must be selective in order for evolution to occur. If one of these principles are broken, evolution will occur as seen in this experiment.
	The evolution of the flat periwinkle is a relatively simple case of a population’s necessity to survive against the crabby predator. However, that in itself is a bit of a misnomer as periwinkles do not decide out of the blue to grow thicker shells. The process of evolution is a brutal and time consuming process that slowly replaces an unwanted allele with a superior allele, or in this experiment’s case a thicker shell to ward off green crabs. Evolution is nothing more than trial-and-error with higher stakes, there is nothing altruistic to be found in the periwinkle’s upward battle against the crabs: it’s a free-for-all with the strongest surviving to reproduce and the weak perishing or unable to reproduce for various reasons. The problem with most populations is that nature is quite unforgiving. While it is simple to look at a sheet of paper and comprehend the workings of evolution, it is happening all around us. Thousands upon thousands of organisms have gone extinct over the millennia that the Earth has hosted living organisms. Simply put, evolution is simple on paper but quite complex in actuality. As mentioned earlier, if the population isn’t divergent enough in diversity, the only hope for their continued survival is the process of mutation. Genetic mutation generally lowers an organism’s Darwinian fitness by but in chance cases genetic mutation can lead to beneficial traits emerging. For instance, the tuberculosis gene can mutate into producing rifampin resistant traits. ((Cite from book.))

The reproduction of this experiment cements the validity of Darwin’s claim of natural selection and evolution. yada yada