Study Guide Exam #3: Species interactions in communities

In order to succeed on the coming exam, you should be able to answer questions like these. It is impossible to include on this study guide all questions that could appear on the exam. It is also impossible to include on the exam every question relevant to the lecture material. The study guide is based on a projection of what is likely to be covered in lecture by the time of the exam.

1. What is mutualism? Be able to define and to give examples of obligate and facultative mutualisms. What kinds of costs are associated with mutualisms and why are the costs sometimes important?

2. What are the two types of mycorrhizal fungi? How are they different? How are they similar? What are the costs and benefits of mutualisms involving these fungi and their host plants?

3. Explain how environmental conditions can determine whether an interaction between two species may be mutualistic or parasitic. Be able to evaluate an example, and to generate predictions.

4. How do resource competition models differ from Lotka-Volterra competition models? What new insights or knowledge comes from extending our investigation beyond Lotka-Volterra models to resource competition models?

5. How may predation influence community structure? Be able to give examples.

6. What is a community? Be able to give examples.

7. What is the difference between intraspecific and interspecific competition? Between resource and interference competition?

8. What is competitive exclusion? Does it occur in experiments? Is it observed in nature? Be able to give examples.

9. Know how to interpret and to use predator-prey isoclines. What are the predictions that result from predator-prey isoclines? What actually happens in laboratory studies? In nature?

10. Explain the keystone predator concept, and why it is important in community ecology. Be able to give examples.

11. Is interspecific competition common in nature? Is it likely to lead to competitive exclusion? How is exclusion avoided? Know some examples, and be able to give evidence to back up your statements.

12. What is character displacement?

13 What is resource partitioning? Why is it important? How does an organism's size seem to be related to resource partitioning? What is the evidence?

14. Explain what limits the distributions of barnacle species in the rocky intertidal.

15. What is resource partitioning? What is the experimental evidence for size-based resource partitioning? How are such experiments done, and what are the predictions to be tested?

16. An investigator does an experiment in which he documents a keystone predator effect in a community of insects. He claims that this result shows that competition is unimportant in this insect assemblage, and that predation is of primary importance in this system. Is the investigator correct about the relative importance of competition and predation in this system? Explain why you either agree or disagree with him.

17. What patterns or processes are illustrated by: Darwin’s Finches; Anolis lizards; rocky intertidal invertebrates, Gause’s Paramecium, Rabbits and Myxomatosis, dragonflies and tadpoles. Know how the experiments or studies were done and the results, and the importance of these examples.

18. What is the intermediate disturbance hypothesis? Is there experimental evidence for or against this hypothesis? Be able to give examples. How is it related to predation?

19. What are the different forms of exploitation.

20. What are the 3 major kinds of species interactions? How do they differ? How do they affect species population growth rates?

21. What are indirect effects? Are there any good examples of indirect effects in communities? What kinds of manipulations are necessary for documenting indirect effects (HINT: Try to generalize from the example involving rocky intertidal invertebrates).

22. What evolutionary effects can be produced by interspecific competition?

23. What community level patterns or processes are illustrated by bird predation on rocky intertidal invertebrates. Be able to explain in detail the importance of each of this example.

24. Consider the following: A species of crayfish (Rusty crayfish) is newly introduced into lakes in Wisconsin. As it spreads, a native species of crayfish (Northern crayfish) decreases in abundance in lakes where it was common. Is interspecific competition a reasonable hypothesis for this observation? What additional biological information would you like to have to evaluate this hypothesis? Design an experiment to test whether interspecific competition is a good explanation for this observation.

25. At LEFT is a diagram showing direct species interactions among old-field arthropods. Suppose you remove the mantis and find that abundance of grasshoppers decreases, and abundances of wolf spiders and plant bugs increase. Give at least two hypotheses indicating how indirect effects may be producing these outcomes (HINT: your hypotheses should state which of the direct paths are important and which are not). Describe at least one experiment that would test which hypothesis is correct. What experimental outcomes are predicted by each of your hypotheses?

26. What are Fixed Quota Harvesting and Fixed Effort Harvesting? What is maximum sustainable yield (MSY)? Why is it desirable? Be able to draw and to interpret graphs related to harvesting from the wild. What problems arise when trying to implement MSY?

27. What is biological control? Give some examples. What are the types of biological control that we discussed in the lectures? What are the characteristics of organisms that can be useful biological control agents?

28. How do predator-prey isoclines relate to biological control, and why may stability of predator-prey systems affect the outcome of biological control.

29. How did myxomatosis virus evolve after it had been introduced to Australia? How does this pattern of evolution related to the discussion of evolution of virulence earlier in the course?

30. The figure at LEFT relates to the problem of harvesting a wild population. Explain this figure in as much detail as you can. What are lines 1 and 2, and how do they differ? What does the curve describe, and why is it shaped that way? Describe what the harvesting modes depicted by lines 1 and 2 predict for the population being harvesting .

31. What is species diversity? What are its two components?

32. What are Dominance-Diversity plots (also known as species abundance curves?). Know how to interpret Dominance-Diveristy plots.