Population and Community Ecology
Problem Sets

Barnard College


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Problem Set Number One
Name________________________

1. Describe the most applicable level of ecology, type of data, mode of inquiry, and level of explanation to test the following observation within a single species: Birds living on oceanic islands tend to have a smaller clutch size than the same species breeding on the mainland. Briefly (in a sentence or two) justify your answer.









2. Calculate the missing values of the following cohort life table and tell what type of population survival curve would be derived from this data.
x
nx
dx
lx
qx
ex
0-1
75
5
1.0
0.07

1-3
70




3-5
68




5-7
66




7-9
63




9-11
10




11-13
3







3. How would a population grow given the following exponential growth model parameter values. Justify your answer with a one-sentence explanation.

a. r = -0.0001


b. b = d


c. Variance in r is four times the average r value


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Problem Set 2 - Competition
Name________________________

1. Contrast the two types of competition and give an example.
















2. Explain how alpha and beta are related to each other? What are the units on these coefficients?






















3. What would be the ultimate outcome for both competitors in each of the following sets of conditions?
a. K1 = 200, K2 = 100, alpha = 1.5, beta = 2



b. K1 = 100, K2 = 200, alpha = 1.5, beta = 2



c. K1 = 200, K2 = 100, alpha = 2.5, beta = 1.5



d. A parasite is introduced that equally impacts both competitors when both competitors are at equilibrium in a situation that is essentially an unstable equilibrium



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Problem Set 3 - Predation, Herbivory, Parasitism
Name________________________


1. Describe the coevolutionary arms race for a parasite-host relationship in your own words. What is the outcome? What is the situation at equilibrium? If there is an equilibrium, describe it. Who is the primary selective force for each of the participants?













2. Label the axes and isocline intersections on this graph. The herbivore population is the dashed line and the plant population is the solid line. Draw the individual and sum vectors for joint populations disturbed from the isoclines. What would be the relative abundance of both species at equilibrium?













3. Incorporating a carrying capacity for the prey (victims) into the predator-prey model makes the system more stable than the exponentially growing model. Why? Why is the base model, which relies upon exponential growth, less stable and more prone to extinction than when a carrying capacity for the prey is instituted?











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Problem Set 4 - Ecotones, Diversity, and Succession

Name________________________

1. What are ecotones and how may they contribute to the generation of biodiversity? How were they conceived of previously to the Smith et al. study from 1997? Why should ecotones be conserved?














2. How do species diversity, resilience, and stability relate to each other? What do each of these terms mean? Address the idea that diversity promotes ecological stability - argue for and against this idea.














3. With relationship to the idea as to why the tropics are so much more diverse than other ecosystems, answer this question using a Proximate Abiotic Explanation, an Ecological Proximate Explanation, and an Ultimate Explanation. What data would you need to gather to answer this question? How would you design an experiment to test AND SUPPORT each of these three explanations.


















4. Explain the mechanisms through which succession occurs and the categories of organisms that play roles at each stage in the process. How do the three types of succession differ from each other?











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Problem Set 5 - Patterns of Resource Use

Name________________________

1. What is an MVP? How is it arrived at? What are four possible properties of the biology of the organisms assumed by the principle?















2. When we were discussing the metapopulation analyses, nearly all of our analyses came to the conclusion that it was better to split a single population into several smaller populations. Stiling (p. 389) says that it is better to do just the opposite. How could this be? What value would have to be changed and in what way for Stiling’s conclusion to be true? How would this variable have to be changed for our earlier conclusions to be valid?

















3. Explain Griffith’s conclusion derived after studying data from restoring animals to the ecosystem: a.) Using trophic level analyses, explain why herbivores could be more successful invaders than carnivores; and b.) Why larger populations are more successful than smaller ones (use population growth models to explain this). Continue on back if needed.









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Problem Set 6 - Human Environmental Manipulation

Name________________________


1. Slash-and-burn agriculture is common in many tropical countries. Forests are cut, burned, and crops are planted in the cutover areas. Yields are usually good the first year, but rapidly decline thereafter. Why?
















2. What is the theoretical relationship between introduced pest species and biological control? Why do the two fields of study usually intermingle?















3. Why is it usually postulated that biological control works best on island rather than continents? Use both metapopulation dynamics and food web theory to answer.











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Problem Set - Diversity Indices

Name________________________

   1. Compute the rarefaction richness index values for these two sites.  Which is richer?  When is the rarefaction index more appropriate than diversity indices?

Number of Individuals

Species                        Site A                    Site B

A                                 45                                 1
B                                  0                                   2
C                                 0                                   3
D                                 0                                   1
E                                  37                                 0
F                                  0                                   1
G                                 0                                   1
H                                 0                                   3
I                                   0                                  2
J                                   20                                2
K                                 0                                   1
L                                  0                                   2
M                                 0                                   3
 

2. When would you use the Shannon diversity Index instead of the Brillouin?   When would the opposite hold true?   What are the weaknesses/assumptions of each index?

 

 

 

 

 

 

 

3. What is an ordinal diversity index and how does it differ from cardinal diversity indices?  How would you do an ordinal index if you were interested in preserving the sites that had the greatest number of insect herbivores?   (Don’t actually work it out using numbers, just briefly summarize.)









 

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Last modified: 15 Apr 03, Prof. James Danoff-Burg