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slatkin11Answers - Bio 1B Spring 2007 Evolution section 1...

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Bio 1B, Spring, 2007, Evolution section 1 of 3 Updated 3/20/07 11:39 AM Lecture 11 11 Molecular phylogenetics. Reading:7th edition 506-507; 6 th edition 503-505. Using cladograms to understand evolution Mapping changes on a cladogram If the cladogram is known, then the minimum number of transitions of a particular character can be inferred by using the principle of parsimony. The true number of transitions may be greater, but for many purposes the minimum number is sufficient. Wings in mammals evolved only once. Characteristics associated with eating ants and termites evolved three times in mammals. The number of times a character changes indicates how difficult it is for natural selection to cause that change. Wings in insects evolved only once. The loss of wings occurred independently in many groups, including fleas, stick insects, parasitic lice and many groups of cave-living insects. Molecular phylogenetics can be used to understand recent evolutionary history. HIV By assuming a molecular clock, the origin of HIV in humans is dated to the 1930s. mtDNA Because mtDNA is maternally inherited, the phylogeny of a sample of mtDNA is a tree that represents the ancestry of females.
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