Midterm1-spring2003-key

# Midterm1-spring2003-key - Name KEY Page 1 of 10...

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Name: KEY 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 not please give your answer by showing how you would make the calculation: e.g., showing "(10+10)/4" is as good an answer as "5" (writing down an appropriate equation and clearly defining the variables, as well as indicating their values, if known, will also suffice). --If you get hung up on a problem, skip it; return to it after you’ve answered the “easy” problems. GENERAL ECOLOGY PCB 4044 SPRING 2003 MIDTERM I PAGE POINTS POSSIBLE SCORE 2 12 _____ 3 12 _____ 4 11 _____ 5 12 _____ 6 10 _____ 7 10 _____ 8 9 _____ 9 15 _____ 10 9 _____ _____ _________ TOTAL 100 _____

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Name: KEY Page 2 of 10 1. A species of salamander ( Salamandrous imaginarius ) occurs on mountains only at elevations below 2,000 m. A second species of salamander ( S. secondarius ) rarely co-occurs with S. imaginarius but is frequent at sites >2,000 m elevation. A species of predatory snake ( Serpentes caudatovore ) also is restricted to elevations >2,000 m. a) (6 points) Develop three separate hypotheses that could explain the observed distribution of one of the three species (i.e., focus on either the snake or one of the salamanders). Each hypothesis should emphasize a different process. A variety of approaches could be taken. Here’s one option focusing on the first salamander species. The distribution of S. imaginarius might be explained by one (or more) of three very general hypothesis. 1) S. imaginarius is absent from higher elevations because it is competitively excluded by S. secondarius ; 2) S. imaginarius is absent from higher elevations because of predation by Serpentes caudatovore . 3) S. imaginarius is absent from higher elevations because abiotic factors: e.g., the physiological tolerances of S imaginarius may be such that they can not live at elevations greater than 2,000 m due to the low temperatures. Note that there are many more possibilities and that these three hypotheses might work in combination to limit the distributions of this species. b) (6 points) Design an experiment to distinguish among the three competing hypotheses. Include all relevant information, including details about the key components of a well designed experiment. Also be sure to mention what you will measure and what you should “see” if the different hypotheses are correct (and what you should see if it is incorrect). A number of different answers are possible (depending on the answer to part a). Here’s one possibility. Conduct an experiment using large enclosures/exclosures. Replicate each treatment (e.g., 3 reps/treatment) and randomly assign treatments to cages (within an elevation). Treatments: 1) predators (S. caudatovore) excluded but competitors present at ambient density, >2000m; 2) competitors (S. secondarius) excluded but predators present at ambient density, >2000m; 3) predators and competitors present at ambient densities >2000m; 4) predators and competitors absent, >2000m; 5) predators and competitors absent, <2000m.
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