Midterm1-2004-Fall

# Midterm1-2004-Fall - Name Page 1 of 10 Instructions-Write...

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Name: Page 1 of 10 Instructions: --Write your name on all the pages --Make sure that all 10 pages are attached. --You may not use calculators or other electronic aids. The math needed to solve a problem should be relatively simple. If you can't do the math, just show what needs to be calculated (e.g., "answer = .5 x .3") --If you get hung up on a problem, skip it; return to it after you’ve answered the “easy” problems. GENERAL ECOLOGY PCB 4044 FALL 2004 MIDTERM I PAGE POINTS POSSIBLE SCORE 2 16 _____ 3 13 _____ 4 12 _____ 5 7 _____ 6 12 _____ 7 6 _____ 8 14 _____ 9 10 _____ 10 10 _____ _____ _________ TOTAL 100 _____

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Name: Page 2 of 10 2-1. An herbivorous insect (known as Species X ) occurs on several islands off the coast of Florida, but is absent from the mainland. Two others species show the opposite pattern: an insectivorous bird and a close relative of the insect (also an herbivorous insect) occur only on the mainland (but not on the islands). You know nothing else about the system a) (6 points) List two hypotheses that might explain the absence of Species X from the mainland (each hypothesis should emphasize a different process). 2-2. (10 points) For each of the following, explain why it is an essential element of a well designed experiment. Replication Controls
Name: Page 3 of 10 3-1. (6 points) A population grows according to the standard logistic equation (without time lags). At very low densities (close to zero), the per capita growth rate is 0.40 / year. At a density of 70, the per capita growth rate is zero. Draw out the trajectories for populations that begin at three different initial densities (N=10, N=50, and N=90). 0 20 40 60 80 100 Time Population density, N 3-2. A bird forages optimally. At the following densities it attacks and consumes all three types of insects in the environment. The insect prey have the following characteristics (we do not know encounter rates, but capture probabilities for all three prey = 1.0): Prey type net energy content (Joules) handling time (seconds) density (no./m 2 ) mosquito 1 1 6 damselfly 5 10 2 mayfly 30 10 1 a) ( 2 points) As densities of all prey are increased (by the same factor), will the predator's diet eventually become more specialized (or will it not change)? b) ( 2 points) If it does change, which prey type will be dropped from the diet first?

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