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Bio1020, Diversity of Life: January 29.docx

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BIOL 1020
Robert Laird

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January 29, 2014 – Biology Exam 1 • Testing center • 90 minutes : 60 minutes worth of content • 50 points • Multiple choice, short answer, short paragraph Review Session: • Iclicker quiz and questions: not for grades! • Two sessions January 31 at 5 in PE264, February 1 at 2 pm PE264 • Sessions are identical Tree building: • Rotations around the nodes (common ancestors) don’t change the evolutionary relationships • The right tree? Many trees that are similar with a few different branches. Trees are always updated. • Parsimony o Tree construction is based on two main concepts  Principle of parsimony: assumption that evolution proceeds by a smaller rather than a larger number of events, note that other assumptions are possible for tree-building (maximum likelihood)  Shared, derived homologies: carry information for designing trees. Derived means non-ancestral (new trait). They are important because they are branching points. Represents a new branching point. How do we know if something is derived? Not present in the ancestral sequence. What is derived and what is ancestral is perspective (hair on mammals)  Such traits called analogous structures or homoplasies are not useful in creating evolutionary trees (they don’t help because they aren’t ancestral) • Distinguish homology or anology: fossil evidence (did the structures arise independently in different ancestors: analogy: Yes, Homology: NO) o Complexity: the more complex two similar structures are, the more likely it is that they are homologous • Construction of phylogenetic trees (majority done in lab) o Choose a study group o Designate the outgroup  Outgroup is a species or a group of species that is closely related to the ingroup (the various species being studied)  The outgroup is a group that has diverged before the ingroup
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