Download STUDY GUIDE FOR THE FIRST MIDTERM:

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PLANT ECOLOGY: STUDY GUIDE FOR THE MIDTERM
HELPFUL HINTS:
Know what a frequency distribution (histogram) is.
Know what a mean is.
No, I will not ask you for formal definitions. Yes, you need to know what things are.
Don't forget: an experiment (=manipulation) is not the same as an observational study.
EQUATIONS:
For all equations from lecture: If I give you the equation,
1. You should be able to define and explain all of the terms, and
2. explain what is the point of the equation: what is it used for? What is the take-home message?
In addition, you DO need to memorize many of the key equations from lecture, for example, equations for
H, Gst, s, inbreeding depression, and 13C as a function of CO2 concentration.
For all equations in the book: if I give you the equation, and some context,
1. You will not be expected to define all the terms, but
2. You SHOULD understand the take-home message.
GRAPHS:
You should be able to both UNDERSTAND, and generate from memory, all of the fundamental graphs
(as opposed to particular examples of data, which I would not ask you to memorize) we went over in class.
For example: “Draw the relationship between water potential and water content.”
Pay special attention to the labels on the axes!!
EXAMPLES:
No, DON’T memorize the names of all the authors on those papers, or of the organisms they studied. DO
know the take-home message for every example. Also, think about things like: “How could they have
done this study a little differently?” Or “What is the next experiment they should do?”
STUDY QUESTIONS:
(At least two of the exam questions will be taken directly from this list.)
1. Describe two or three experiments (or observational studies) you could do easily with plants that would
be very difficult or impossible to do with animals. Be sure to specify the question you are asking with the
experiment.
2. Serpentine soils create a unique habitat in California, and harbor a unique endemic flora (plants not
found anywhere else). There is a great deal of controversy over exactly why most plants can not (or do
not) live on serpentine soils. Here are three alternative explanations for what limits plant growth on
serpentine:
a. High levels of toxic heavy metals such as nickel, lead, and chromium.
b. Low levels of nitrogen and phosphorus.
c. Low calcium to magnesium ratio.
Describe an experiment, or set of experiments, you might use to try to distinguish between these
possibilities.
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3. High in the Sierras, you come across a series of alpine meadows. In one meadow, all of the alpine
skunkflowers (Potenta smellii) are pink; in the next meadow, all flowers are white. Describe an
experiment you might do to determine if this pattern was caused by natural selection rather than genetic
drift.
4. Would it be difficult to prove that the pattern was definitely caused by genetic drift? Why?
5. Clausen, Keck, and Heisey drove over Route 120 checking out plants. They found that individuals of
the species Achillea lanulosa were bigger at low elevations than at high elevations. What could be two
alternative explanations for this?
Describe an experiment you could do to distinguish between these explanations.
6. What is a G x E (“G by E”) interaction? Draw a graph that demonstrates one. What was the experiment
that generated that graph? (Look in your book: phenotypic plasticity.)
7. Give the equation for the selection coefficient. Give the steps you would go through to estimate the
strength of selection (and if there is any selection) against poison oak plants with low concentrations of
toxic oil in their leaves. Design an experiment to figure out whether the selection for toxins is caused by
large herbivores like deer.
8. In the year 2050, we send out 15 colonies of mini “Biosphere II” communities into outer space. In each
space station we start a population of Kentucky bluegrass. All populations were started from the same
diverse seed lot. What do you predict will happen to the allozyme diversity within each space station
population over time (i.e. increase or decrease)? What will happen to the diversity among the different
space stations? Explain.
9. Imagine that due to some unforeseen buffering effect of the oceans, atmospheric CO2 concentrations
stop increasing. However, an increase in other greenhouse gases results in dramatically increased global
temperatures. What do you predict will happen to the outcome of competition between C3 and C4
species? Explain the physiological mechanism behind this.
10. You are interested in the evolution of the ancestors of cattle and horses, which at some point changed
from browsing herbs and shrubs to grazing on grasses. How might you use stable isotopes to try to
pinpoint when that shift in diet and habitat use occurred? Include an explanation of the physiological
basis for your argument.
11. Both C4 and CAM species take advantage of the enzyme PEP carboxylase to improve their ability to
photosynthesize under conditions of extreme water stress. What are the characteristics of PEP
carboxylase that make it well-suited to the photosynthetic process in a) C4, and b) CAM plants?
Another way of stating this question is: what aspects of PEP carboxylase make C4 and CAM possible?
12. How many extra ATP’s are used up for every carbon assimilated using CAM photosynthesis relative
to C3 photosynthesis? Just kidding.
13. You are working on developing your own heirloom variety of grape that requires less irrigation. How
(and when) could you use a pressure bomb to choose the most drought-tolerant genotype in your
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experimental garden? How could you use stable isotopes to answer the same question? Why are these
two approaches complementary in terms of what kind of information they provide?
14. You are interested in the water status of a species of shrub, Oscar dleonii, which lives on both the
south-facing and north-facing slopes of a ravine. Are the plants on different slopes locally adapted to their
locations? Draw the relationship you expect to see between water potential and water content (pressurevolume curve), under the hypothesis of local adaptation or acclimation. What experiment could you do to
determine whether the differences are caused by acclimation or adaptation?
15. Why are mycorrhizae and Rhizobia not even close to the same thing?! Which is more associated with
nitrogen nutrition of plants? Why? Which is more associated with phosphorus nutrition of plants? Why?
16. If you snuck out in the middle of the night and dumped a bunch of nasty, microbicidal (=kill bacteria)
chemicals on the ground, would you be likely to have a bigger effect on the nitrogen cycle or on the
phosphorus cycle?
17. You suspect that your neighbor’s Norway spruce, which drops acidic needles, may be affecting the
cation exchange capacity of the soil in your garden. How would you explain this to your neighbor when
you ask him to cut down the tree?
18. The presence of Lupinus arboreus at Bodega Bay exerts a large influence over plant species
composition. Maybe you remember from the slides that there are native lupines in these coastal prairies as
well. What series of studies and/or experiments would you use to try to figure out whether the smaller
native lupines have a similar, albeit less dramatic, effect on species composition?
19. The annual herb Albita cantanta produces two flowering stalks. You are interested in whether this
herb is limited by pollinators, so you hand-pollinate one randomly-chosen stalk on each of 20 plants. At
the end of the season, you count the number of seeds on hand-pollinated and “naturally” pollinated stalks.
You also count the number of seeds on one stalk of 20 other randomly-chosen plants. Here are the data
for mean seed number (plus/minus a standard deviation):
--------Originally manipulated plants---------Naturally pollinated
Hand-pollinated
1201 +/- 120
1872 +/- 102
----Other plants----Naturally pollinated
1480 +/- 107
How do you interpret these data?
20. You are interested in a rare tropical orchid that co-occurs with and appears to mimic a weedy species
of lily that grows along forest edges and makes a lot of nectar. Design an experiment to see if the orchid
acts as a “cheater” in the relationship between the lily and its pollinators.
21. Some species of lavender have big, showy purple bracts. You suspect the reason for these bracts may
be to promote outcrossing by attracting bees carrying pollen from other patches of lavender. You would
like to identify the pollen source for seeds produced by plants in a small patch. You decide to use genetic
markers to determine whether the fathers came from among the few individuals in your patch or from
somewhere else outside the patch. Will you be using allozymes or chloroplast DNA and why?
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22. If you find that most of the seeds have fathers from somewhere outside the patch, do you suspect that
inbreeding depression (as defined in class, not genetic load) would be low or high in this patch, and why?
23. Even though most seeds seem to have fathers from outside the patch, say you find that most of the
adults in the patch are nearly genetically identical. What do you suspect about local adaptation in this
species?
24. Why do plants with very high rates of self-fertilization (e.g. Epilobium ciliatum) tend to produce very
few pollen grains? Put this in the context of the theory of sex.
25. In a paper on the tropical rain forest tree Tetragastris panamensis, Henry Howe writes: "Wide
geographic ranges of this tree and members of the frugivore assemblage, use of other food resources by
common foragers, richness of the assemblage, variation in species visitation at individual trees, irregular
annual fruit production, and obvious "inefficiency" of the dominant dispersal agents from the perspective
of the plant suggest that Tetragastris has a generalized dispersal strategy…" Do you expect Tetragastris
to coevolve toward a specialized relationship with its dispersers? What are the limits to specialization in
this system?
26. You have done studies on an ant-dispersed shrub, Willi colonium, which shows strong patterns of
“Janzen-Connell effects”—meaning that the distribution of seeds is more aggregated around the parent
than the distribution of seedlings, which is in turn more aggregated than the distribution of young adults.
There are two species of ants that you commonly find carrying seeds of Willi colonium, call them
Ant 1 and Ant 2. They may eat the seeds, or they may just carry and drop them. You want to determine
which is a better disperser. What are the pieces of information you need? (Write this in outline form) For
each piece of information, what kind of study or experiment would you need to do to get the information?
(Just as an aside: imagine how complicated this could get if you believed that seed predation by
one or both of the ants was CAUSING the Janzen-Connell pattern! You would probably need to build a
mathematical model to figure it out. I would never ask you a question that hard.)