PLANT ECOLOGY: REVIEW QUESTIONS FOR THE FINAL

Hints and reminders:

Equations: yes. Including, and especially, how matrix models work!

Graphs: yes. Know the axes. Focus on interpreting data.

Definitions: no.

At least two of the exam questions will be taken from the list of study questions.

STUDY QUESTIONS:

  1. As part of your job as a molecular plant breeder, you discover a radish with a phytochrome mutation: under certain conditions, the phytochrome molecule can not respond to far-red light. Therefore the phytochrome is always in its active form. If you bred this mutation into wild radish, a noxious weed, what impact might it have on the ecology of the weed? Do you predict that this mutation would last and spread within weedy radish populations?
  1. Design an experiment to determine if a plant population is seed limited or safe site limited. Draw a graph, and label the axes, showing the pattern you would expect to see for each outcome.
  1. Give a biological explanation for Yoda's Law. What does it assume is the ultimate limiting resource to plant populations?
  1. Design an experiment, using basil plants as a model system, to show that the -3/2 rule works: How would you set it up? What would you measure? When would you take measurements? Modify your experiment to investigate the assumption in the previous question (i.e. that X is the limiting resource constraining the relationship between biomass and density).
  1. Design your own plant species. What is its life history? Where does it live, how does it reproduce, and how often? How long does it live, and how old are most individuals when they die? How big does it get?
  1. Give a biological explanation for Yoda's Law. What does it assume is the ultimate limiting resource to plant populations?
  1. Design an experiment, using basil plants as a model system, to show that the -3/2 rule works: How would you set it up? What would you measure? When would you take measurements? Modify your experiment to investigate the assumption in the previous question (i.e. that X is the limiting resource constraining the relationship between biomass and density).
  1. What is a stage-structured model? Why are stage-structured models more appropriate than age-structured models for most plants?
  1. Design an imaginary plant species. What is its life history? Now translate that life history into a stage-structured model. Make a matrix to represent the life history of the plant, incorporating all the transitions between life stages. Think through what kind of numbers would go into each entry in the matrix.
  1. Now imagine a whole population of your plant. Start with a stage structure that makes sense to you (redwood trees in a forest: 100 adults, 1 juvenile, 1 seedling, 10000 seeds; or thistles in a newly ploughed field: 0 adults, 0 rosettes, 0 seedlings, 1000 seeds). Using the matrix you built, project that population one year into the future, two years, three years.

Now that you've done that, do you think the numbers you chose for the matrix make sense?

Practice going back and forth between the biology and the math…what DOES that number mean, really?

  1. Give an example of a way that a matrix model could help guide the management of an endangered plant species.
  1. What is the problem with simple additive designs for competition experiments? What are the two things that you cannot distinguish with such a design?
  1. One of the great mysteries of ecology is: How can so many different plants coexist in one place?
  1. Why is this a mystery, from the perspective of competition theory?
  2. What are some theoretical explanations for this mystery? You should understand and be able to explain the following:

Niche partitioning

The intermediate disturbance hypothesis

The competitive ability/resistance tradeoff

The competitive ability/dispersal tradeoff

  1. In the Werner and Platt example, 6 species of Solidago (goldenrod) showed much less niche overlap in natural prairies than they did in a plowed field. Draw two graphs that illustrate the result (what did they measure, anyway?) How do you interpret this result? Which graph illustrates the fundamental niche and which illustrates the realized niche?
  1. How would you use input ratios and output ratios to predict the outcome of competition between two plant species?
  1. You notice that under thick stands of Scotch broom, very few native species seem to grow. This might be due to competition for light or moisture or some other nutrient (probably not nitrogen: why?). Or it might be due to allelopathy. Design a series of studies./experiments you would want to do to test for allelopathic effects:

A. Show that Scotch broom leaf tissue is potentially toxic

B. Show that these toxic compounds are really responsible for the pattern you see.

C. What might you do to try to figure out WHICH compounds are involved?

D. What is an alternative explanation you would want to test for?

  1. You are interested in trying to distinguish between the plant stress hypothesis (that herbivores are attracted to the most stressed plants) and the plant vigour hypothesis (that herbivores are attracted to the healthiest plants). Design an experiment to do this.
  1. What is the "stress"?
  2. What is your design?
  3. Draw a graph for each scenario, showing the pattern you would expect under each hypothesis.
  1. Hypericum (St. Johnswort, Klamath weed) was a terrible pest plant in California until a biological control beetle was introduced to control it. Now people want to breed St. Johnswort with high chemical concentrations of hypericin, which may act as a defense against herbivores. If you were the USDA official in charge of deciding whether this plant breeding program should be allowed, what information would you want to know?
  1. A farmer has a grapefruit orchard with two varieties of grapefruit trees. One variety is resistant to the citrus canker bacteria (Xanthomonas campestris) and the other is not. The farmer wants to know whether he will be able to harvest any juicy grapefruits this year.

A. Outline the disease triangle for the farmer.

B. Using the gene-for-gene paradigm, describe to the farmer the conditions when the grapefruit trees will be diseased.

C. Using the gene-for-gene paradigm, describe to the farmer the conditions when the grapefruit trees will NOT be diseased.

  1. Give an example of a chemical defense. Give a couple of examples of plant defenses that have been co-opted by humans.
  1. Contrast the views of F. Clements and H. Gleason on:
  1. What is a plant community? Draw a hypothetical distribution of species over an environmental gradient under each concept of community.
  2. What is succession and how does it work?
  1. What is the role of 1) stochastic and 2) deterministic factors in the development of plant communities?
  1. What are some examples of stochastic factors that can be important?
  2. What are some examples of deterministic factors that can be important?
  3. Design a study or experiment to quantify the relative importance of stochastic vs. deterministic. Chose a particular system (study site, habitat, set of species) for this study: based on what you know about the system, do you think stochastic factors will dominate, or deterministic factors?
  4. If you did this study at your "Real Ecology" site…do you think it would be stochastic or deterministic factors?
  1. What kinds of ecological questions can you answer with ordination? Why is it useful? How do you do it?
  1. Design a plant ecology observational study or an experiment that a group of four could do in 4-6 hours on the UCSC campus natural reserve. State: 1) your question, 2) your methods, 3) your expected results, and how you would interpret alternative patterns in the data. 4) Draw a graph of your expected results.