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Unformatted text preview: Lecture Goals: Lecture 11 Describe the goals of the field of phylogenetics. What is a phylogenetic tree? 1. To show current species, areas of possible extinction, and areas where speciation occurred. 2. To show the related ness between different organisms. 3. A branching diagram or " tree " showing the inferred evolutionary relationships among various biological species based upon similarities and differences in their physical and/or genetic characteristics. Explain the difference between a rooted tree and an unrooted tree.- Unrooted tree- shows the relatedness of the leaf nodes without making assumptions about ancestry at all- Rooted tree- Shows the related ness between organisms linked to the most common ancestors (includes terminal taxa, node, internal branch, peripheral branches , and outgroups . Label the parts of a phylogenetic tree. Define monophyly, paraphyly, and polyphyly and provide examples when given. 1. Monophyly- a group that includes an ancestor and all of its descendents 2. Paraphyly- at least one of the descendents is excluded (humans) 3. Polyphyly- at least one excluded member is ancestral to some of the others Explain how to build a character matrix, and be able to define all of the terms involved. Build a phylogenetic tree from a character matrix. Which types of characters provide you with useful information? What is an outgroup, and why is one necessary? 1. Outgroup- group of organisms that serves as a reference group for determination of the evolutionary relationship among three or more monophyletic groups of organisms. a. Hypothesized to be rather closely related to the other groups, but less closely than any single one of the other groups is to each other. 2. Synapomorphy- Character states are only informative if they are shared and derived Map a character on a tree. Define parsimony and explain how this principle is used in phylogenetics. 1. Parsimony- the tree with the fewest evolutionary changes is most likely to be right Lecture Goals: Lecture 12 Define homoplasy and explain why it poses a problem for phylogenetic analysis. 1. Homoplasy (analogous)- similarity that is NOT inherited from a common ancestor 2. Because it causes more changes in an phylogenetic tree and it bring into question whether the tree was constructed correctly. List three evolutionary sources of homoplasy and provide examples when given. 1. Convergent evolution- the acquisition of the same biological trait in unrelated lineages a. octopus eyes b. saber tooth c. spots and stripes 2. Parallel evolution-- the acquisition of the same biological trait where the ancestors considered were also similar a. Butterfly wings 3. Evolutionary reversals- random back mutations a. frogs growing teeth Explain what is meant by the term comparative method....
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