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Unformatted text preview: Avian Biology Exam #2 Spring 2010 Name ______________________ Please answer all questions. Adjust your time according to the point value of each question. Place your name in the upper right corner of every page! This exam is worth 60 points. Good luck! _______________________________________________________________________________ 1a) ( 1 pt) American crows in New York (and probably in Florida) are cooperative breeders. Groups consist of 3-10 individuals, including a socially monogamous breeding pair and 1-8 helpers. The breeding female is the only individual in a group who produces eggs. Helpers are usually, but not always, related to the breeding pair. What do you think is the most likely explanation for why helpers help raise young produced by the breeding pair? Explain in one or two sentences. Photo: A. Townsend b) (1 pt) A study by Andrea Townsend that was published two months ago in American Naturalist revealed that broods of crows often had mixed parentage (i.e., had more than two parents). Re-read the background information provided in part a of this question. In one sentence, explain why the term socially monogamous is used above. c) (2 pts) Why would a female mate with males in addition to her mate? The author of the study provides several hypotheses. One of the hypotheses is called the good genes hypothesis. You learned about this hypothesis when we discussed Bluethroats in class. Please describe the good genes hypothesis. d) (2 pts) As it turns out, female crows in New York mate almost exclusively with males in their group, not with outside males. How do you think that observation either supports or weakens the good genes hypothesis? Explain. e) (3 pts) The genetic diversity hypothesis states that females mate with more than one male to increase the genetic diversity of their brood, which would produce offspring suited to a wider variety of environmental conditions than if all offspring had the same two parents. The author found that young fledged from broods with mixed parentage were not more likely to survive for six months than young fledged from broods without mixed parentage. What do you think she concluded about the genetic diversity hypothesis? Explain. f) (3 pts) The author discovered that broods with greater amounts of mixed parentage received more food from helpers and were more likely to fledge young than broods with lesser amounts of mixed parentage. She used this observation to propose another hypothesis about why female crows seek extra-pair copulations. Try to think of and explain her hypothesis (or another hypothesis that fits the observation). hypothesis (or another hypothesis that fits the observation)....
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- Spring '09