A snail shell, once empty of its original owner, the snail, often tells a story of the life, and sometimes, the death, of that snail. An example is drill holes from predators seen in many marine snails. Some snails kill other snails by drilling a hole in their shells, and sucking out the inside of the snail through that opening. We want to know if the predators, for whatever reason, attack a particular part of the snail shell. In this lab, you do a short study of Turret snails, Turritella leucostoma, collected after the shells washed up on a beach near the town of Puerto Penasco, Sonora, Mexico. You will look at two samples of shells (2 photos with ~15 shells each), and record for each shell in which whorl (turn) of the shell the predation drill hole is located. Then you will make a tally of your data, and use it to make a graph and see if you notice a pattern. and reflect on what the pattern might mean. Finally, you will reflect on the lab, any stumbling blocks and how you solved them, and one follow up question. For a video of how snails drill hole in other snail shells, see https://www.youtube.com/watch?v=Olb5ZIIrUFQ
Look at the two images of shells included with the lab, each with around 30 shells. Consider these all as one sample. There are two photos simply because it was easier to photograph them in smaller groups.
a. Record which whorl the drill hole occurs in each shell in the two images (total around 30 shells). The body whorl of the shell, with the opening, should be whorl #1 and the very tip of the spire would be whorl 10 or so. Your tally for the first ten shells might be, for example, 3,3,5,8,3,2,8,8,3,2. Summarized that would be 4 shells with a drill hole in whorl 3, 1 shell with drill hole in whorl 5, 2 shells with drill hole in whorl 8, and 2 shells with drill hole in whorl 2.
b. Create a graph of your data. Put some thought into this so that the graph or chart is clear. Label the axes or segments in a pie chart, and give the graph a title. Add any images you want to make your graph clearer and more interesting, such as a sketch of a shell with a hole in it as one option.
c. Discuss why you choose the type of graph (line graph, bar chart, or pie chart)? What was it about that type of graph that you thought was the best way to illustrate your data?
d. What pattern do you notice if any? What might it mean in terms of the biology or behavior of the turret snails or their predators?
e. Write one follow up question. What are you are curious about after doing this lab?
f. Was there a stumbling block in doing this lab at any point, where you had to make a decision on how to proceed? This is common when doing investigations and the important thing is to simply describe what you did so someone else could repeat it. For example, "I wasn't sure what was whorl number 3 or 4 on some shells, so I went with the lower number each time." Or " I couldn't see some of the shells clearly enough in the photo, so I left those out."
What to hand in: Submit a typed report to d2l with answers to questions c through f, and a graph of your data. Feel free to ask questions and share ideas about the lab with staff or fellow students on Slack, but submit your own work to d2l (your own graph and answers to the questions).
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