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Unformatted text preview: Work Assigned This Week Due Date 1. Phylogeny Calculations/Trees in lab today Work Due This Week 1. Phylogeny Calculations/Trees (in lab today) Table of Contents Section Topic Page 6.0 Introduction 1 6.1 Building a Phylogenetic Data Matrix 3 6.2 Parsimony Analysis and Character State Changes 3 6.3 Phylogenetic Hypotheses from Phenotypic and Molecular Data 4 6.4 Placement of Extinct Species into Phylogenetic Hypotheses 5 Objectives 1. Define evolution, speciation, phylogeny, shared derived character, monophyly, paraphyly, convergence, reversal, outgroup, ingroup, parsimony, character, and character states. 2. Demonstrate how to read a phylogenetic tree by determining which branches represent extant and ancestral species and the relationships among species. 3. Identify characters and character states in different species. 4. Develop new characters and character states and code them so they can be added to a character data matrix. 5. Explain how the parsimony criterion is used to construct a phylogenetic hypothesis and reconstruct evolutionary changes in particular characters based on the hypothesis. 6. Compare phenotypic and molecular characters to determine whether diverse types of data yield similar conclusions regarding phylogenetic relationships. 7. Formulate a hypothesis for placing an extinct species (fossil) into a phylogenetic hypothesis of living mammals. 6.0 Introduction In 1859, Charles Darwin hypothesized that the similarities and differences among species are the direct product of descent with modification ( evolution ). Assuming life had a single origin, speciation (the splitting of 1 species into 2) must have occurred many times to yield the present diversity of life. Phylogeny , the evolutionary history of a particular group of species, generally is depicted as a branching tree-like diagram (Fig.1). Each branch represents a different species, with terminal branches (A, B, C, D in Fig. 1) being living species, each branch point (Y) represents a speciation event; a species forming the base of the Y is a common ancestor of the 2 descendant sister species above (e.g., lineage E is the common ancestor of B and C). In this tree (Fig.1), species B and C are more closely related to each other than they are to species A or D. That is, species B and C share a more recent common ancestor with each other than they do with either species A or D. Likewise, according to the phylogenetic hypothesis shown, species A, B, and C are more closely related to each other than each is to species D, because species A, B, and C share a more recent common ancestor (ancestral species F). G represents the common ancestor of all species in this phylogenetic tree. Logically, one might expect very recently diverged species to share many more characters than lineages that diverged a very long time ago (e.g., two bird species look much more similar to each other than either does to a lizard species). Biologists reconstruct the phylogeny for a group of species by examining possible...
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- Spring '08
- Evolution, Phylogenetics, character states