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WIDENER BIOL 301 - Short Answer Questions

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ECOLOGY 301 – EXAM 3 Wednesday, 28 November 2001 page 1I. Short Answer QuestionsSAQ #1. Please state and BRIEFLY explain the two major objectives of community ecology.Please use a diagram for each, AND write an explanation.diagram and explain objective 1 - (2 pts)explain the key “emergent properties” that this objective aims at explaining - (2 pts)diagram and explain objective 2 - (2 pts)explain the key “emergent properties” that this objective aims at explaining - (2 pts)The next several questions will asses your understanding of the 2 species competition equations:species 1: species 2: 111111121NNtrNKNK∗ = ∗ − −∗∆∆α 112222212NNtrNKNK∗ = ∗ − −∗∆∆βSAQ #2. One of the principal mathematical assumptions of this model is the constancy of itsparameters. What are these constants and what are the ecological implications ofassuming that these are constants? (3 pts)SAQ #3. Another assumption is about how the model includes density dependence. Pleaseuse the axes below AND explain how this model includes density dependence. (4 pts)SAQ #4. Please explain in words without using any symbols or notation what is the principalprediction of the 2 species competition model above. (3 pts)SAQ #5. It can be shown that stable competitive coexistence will always occur if twoinequalities are true: 121KK>α and 112KK>βShow how EITHER ONE of these inequalities results directly from the 2 speciescompetition equations above. (4 pts) SAQ #6. Consider the two figures below that show the N1 vs. N2 solutions for simulations ofcompetition with two different sets of model parameters.{K1 = K2 = 600, alpha = 1.5, beta = 1.5} {K1 = K2 = 600, alpha = beta = 0.5}For which one is there stable coexistence? A or B (circle one, 1 pt)Please explain why does one lead to stable competitive coexistence but the other does not? (3 pts)A BECOLOGY 301 – EXAM 3 Wednesday, 28 November 2001 page 2SAQ #7. Thomas Park’s laboratory studies on competition betweentwo species of flour beetles found that the winner incompetition depended on the temperature, humidity, andgenetic strain of individual beetles.(a). What are the specific conclusions we can safely drawfrom Park’s studies about the assumptions of our twospecies competition model above? (2 pts)(b) What are the main generalizations we can draw from Park’s studies about the use oflab experiments to understand competition in nature? (2 pts)SAQ #8. At right is a plot of invertebrate speciesdiversity among a rocky intertidal habitats wherethe predatory sea star, Pisaster, is present (top)versus where it has been experimentallyremoved. Please briefly explain this pattern. (3 pts) SAQ #9. Consider the simplest possible model of the predator/prey interaction below:for prey: for predator: 11PreyPreytPredator∗ = − ∗∆∆r α 1PredatorPredatortr Prey2∗ = − + ∗∆∆β(a). Please list two of the principal mathematical assumptions of this model (select twodifferent ones!), and in addition, state the main ecological implications of each of thesemath assumptions.mathematical assumptions: ecological implications: (2 pts) SAQ #10. Draw a little graph below showing the prey per capita population growth rate vs.the predator population size for this model. Indicate ALL relevant constants, and LABELTHE AXES! (2 pts)SAQ #11. Draw a little graph below showing the predator per capita population growth ratevs. the prey population size for this model. Indicate ALL relevant constants, and LABELTHE AXES! (2 pts)05101520251962 1964 1966 1968 1970 1972 1974with PisasterPisaster removedECOLOGY 301 – EXAM 3 Wednesday, 28 November 2001 page 3SAQ #12. Consider the simplest possible model of the predator/prey interaction below:for prey: for predator: 11PreyPreytPredator∗ = − ∗∆∆r α 1PredatorPredatortr Prey2∗ = − + ∗∆∆βa. In the graph below, plot the change in thepopulation size of Prey using four littlearrows corresponding to when Prey andPredators are common and rare.(1 pt.) (1 pt.)c. In the graph at right, combine thearrows from the two plots above...(2 pts)d. Does this model lead to stablepredator prey coexistence? Yes or No ??? (2 pts.)e. Briefly explain why or why not. (2 pts) commonPredators rare rare common Preyb. In the graph below, plot the change in thepopulation size of Predators using fourlittle arrows corresponding to when Prey andPredators are common and rare. commonPredators rare rare common Prey commonPredators rare rare common PreyECOLOGY 301 – EXAM 3 Wednesday, 28 November 2001 page 4Consider again the simplest possible model of the predator/prey interaction below: for prey: for predator: 11PreyPreytPredator∗ = − ∗∆∆r α 1PredatorPredatortr Prey2∗ = − + ∗∆∆βSAQ #13. (a). What is the ecological interpretation of the alpha (α)? (2 pts.)(b). Why might natural selection favor a higher alpha (α)? (1 pt.)(c). At right is a plot of Predator vs. Prey for an elevated alpha(α) (recall that we did this example in class). Brieflyexplain what this simulation predicts aboutcoexistence due to the effects of increasing alpha (α).(1 pt.)SAQ #14. (a). What is the ecological interpretation of the beta (β)? (2 pts.)(b). Why might natural selection favor a higher beta (β)? (1 pt.)(c). At right is a plot of Predator vs. Prey for an elevated beta(β) (recall that we did this example in class). Brieflyexplain what this simulation predicts aboutcoexistence due to the effects of increasing beta (β).(1 pt.)ECOLOGY 301 – EXAM 3 Wednesday, 28 November 2001 page 5I. Longer Answer Questions (15 points each) LAQ #1. Consider the simplest possible model of two species competition below:for


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