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Midterm3-2004-Fall-KEY - Name KEY Page 1 of 8...

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Name: KEY Page 1 of 8 Instructions: --Write your name on all the pages --Make sure that all pages are attached. --Any 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). GENERAL ECOLOGY PCB 4044 FALL 2004 MIDTERM III PAGE POINTS POSSIBLE SCORE 2 20 _____ 3 12 _____ 4 8 _____ 5 14 _____ 6 20 _____ 7 11 _____ 8 15 _____ _____ _________ TOTAL 100 _____ Informational only: UNDERGRADUATE TEACHING ASSISTANTS : Some of our undergraduate courses provide the opportunity for undergraduates to help with the course (as undergraduate TAs). We have seldom done this in Ecology, but it can be a very valuable opportunity for students (they gain advanced knowledge of the subject, great experience, the opportunity to work with an instructor and graduate TAs, and course credit (via Zoo 4940)). If you are interested, please circle all semesters during which you might be interested. Also include your email address (so that we can contact you if future Ecology instructors are looking for undergraduate TAs): Spring 2005, Fall 2005, Spring 2006; Email:
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Name: KEY Page 2 of 8 2-1. (12 points) Define each of the following and explain why they are a critical element of a good experiment. CONTROL(S) A treatment that lacks the factor of interest, but is otherwise identical to another treatment. A control allows the experimenter to isolate the effect of the factor of interest (from cofounding influences). REPLICATION Replication refers to the number of independent subjects that receive a treatment. Because subjects will not respond identically to a given treatment, replication allows the experimenter to estimate the within-treatment variation in the response and thus helps her/him guage whether the observed differences between treatments are real (i.e., exceed the expected difference within a treatment due to sampling error). Increased replication leads to increased power. RANDOM ASSIGNMENT Subjects are assigned to treatments without regard to any trait of the subject (i.e., at random) to ensure that, on average, subjects in two treatments differ only because of the treatments. 2-2 a. (4 points) Define the term “higher order interaction” (also known as a trait-mediated indirect interaction). HOI arises when the strength of an interaction between a pair of species depends upon the density (or presence) of a third species. [In the context of the Lotka-Volterra equations, a HOI arises when a ij is a function of the density of another species (not species i or j).] b. ( 4 points ) Provide a plausible biological example of a higher order interaction. Do not use the Norrisia -Octopus-Barnacle-Lobster example. Your example does not have to exist, but it has to be plausible biologically and illustrate a HOI.
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