For this experiment, I decided to compare the thickness of the shell of the surviving snails in a population that had crabs present and a population that did not have crabs present. I did my experiment on the West side. My Independent Variable was the presence or absence of crabs, the dependent variable was the average thickness of the shell of the snails. The control of this experiment is a tank with no crabs just snails. In this experiment, I did not cull the baby snails. This means that the snails in my experiment can reproduce and I will have baby snails in my experiment.
There were eight tanks in my experiment. I held constant the number of snails and the thickness of snails consistent between the control and treatment tanks. Each tank had 15 snails; 5 of these snails had very thin shells(1-4 mm), 5 had thin shells (4-7 mm) and the last 5 had thick shells (7-10 mm). Four of the eight tanks were my treatment group, they were two crabs in each of the four tanks. The other four were my control group so they did not receive treatment which means there were no crabs in these tanks. I had four tanks in each group because I wanted to have replicates of my experiments.I recorded my data which is the mean of the thickness in each tank, the number of crabs and the snails that survived in each tank. After that, I run the experiment for 120 days. After every 30 days, I recorded the data again till the 120 days had past. I ran the experiment for 120 days to allow the snails to reproduce.