PracticeExamWk4 - Bio180 Fourth Practice Exam Question 1 1....

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Bio180 Fourth Practice Exam Question 1 1. It is common to observe that parasitic species lose genes and other traits over time—probably because they get most of the resources they need from their hosts. Explain why trait loss can complicate efforts to estimate where parasitic species belong on evolutionary trees. Question 1, Sample answer: Evolutionary trees are estimated from synapomorphies—shared traits that are derived from a common ancestor. If certain species that belong in a monophyletic group have lost a large number of traits, it is likely that at least some of the lost traits were synapomorphies that identified them as part of that group. For full credit (2 points), answer must articulate the concepts that 1) synapomorphies (or shared, derived traits) may be missing, and 2) that lost synapomorphies“mask” or “hide” which monophyletic group the parasitic species is actually part of. If one of these two elements is missing or incorrect, award partial credit (1 point). If both of these elements are missing or incorrect, award no credit (0 points). Question 2 Great apes (chimps, gorillas, humans, orangs) and bobcats have reduced tails. Is this similarity due to homology or homoplasy? Explain your logic. Question 2, Sample answer It is due to homoplasy, because the common ancestor of bobcats and great apes had a tail, and it was lost independently in the two groups. The logic here is that other cats and primates (and
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This test prep was uploaded on 04/10/2008 for the course BIOL 180 taught by Professor Freeman during the Fall '07 term at University of Washington.

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PracticeExamWk4 - Bio180 Fourth Practice Exam Question 1 1....

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