Lab 6 Homework—Please type your answers in a color different then black. This helps us grade the assignment. Thank you.
Name
1. Plot each of the five values (number of species, total percent cover, Diversity Index, percent cover on panel, and percent overgrowth) on the y-axis against panel age on the x-axis. “Graph paper” is available at the end of the homework.
2. Provide a caption for each graph that very briefly describes the pattern/result you noticed. Keep it brief. You can hand write these next to each graph, if that is easier. But please make it legible.
3. Look at the graphs. Select one pattern/result that interests you. Propose a hypothesis to explain the pattern and propose that below: For example, you might observe a decline in the number of species over time. Maybe there are fewer species at 9 months than you found at 3 months. What could have led to this decline? We want you to come up with a hypothesis to explain WHY there would be fewer species at 9 months vs 3 months. Was it competition ? Predation? A disease? Increase/decrease in water temperature? Think about an interaction either with other organisms or the environment. In lecture you will learn about facilitation, tolerance, andinhibition—if that was covered by the time you try this lab, you might consider those models.
a. Pattern/Result you are going to provide an explanation for:
b. Proposed hypothesis to explain this result (Try to keep it focused to one explanation —for example, don’t combine predation and competition—think about testing only one factor.
4. Methods: Briefly describe an experimentthat would test your hypothesis. Outline the essential features of the design by describing what you would do and which data you would collect. Your goal is to try to exclude any other possibilities. Don’t just write “I will put the plates out in the water and see what happens.” That would not control for influences of the environment, predation, competition for food etc. For example, if you think a disease resulted in fewer species at 9 months, maybe you could introduce varying diseases to the panels in an aquaria you set up in a lab room and measure the effect. A little cruel to do, but this would test directly if a disease is having an influence.
We could test our hypothesis by:
5. Quite often more than one factor can influence the community structure. This contrasts with what we told you to do in Q3. In hypothesis testing we usually start with just one parameter at a time and build a more complex story as we do more experiments and learn more. With that in mind, what might be another explanation for the pattern you chose to focus on?
