BCladistics - grouping Cladograms Polyphyletic grouping...

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Biological Classification Heyer 1 Cladistics Clade (“branch”) — replace traditional taxon – Groups of organisms presumed to be derived from a common ancestor are organized by bifurcating (two-way splitting) of a branch – Each bifurcation is based upon the acquisition of a new, unique character ( apomorphy ). Maximum parsimony : the branch pattern that can be created with the fewest required steps is most likely the most correct. Cladistics More vocabulary: • A true clade must be monophyletic – must include an ancestor and all of the known descendants of that ancestor. – A grouping that only includes an ancestor and some of its descendants is paraphyletic . – A grouping that includes organisms from different ancestries is polyphyletic . • Derived apomorphic characters shared by members of a clade are synapomorphic . • Ancestral characteristics inherited prior to the branching of a clade are plesiomorphic . Cladograms Monophyletic clades Cladograms Paraphyletic
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Unformatted text preview: grouping Cladograms Polyphyletic grouping Building Cladograms Assemble a table of character states Biological Classification Heyer 2 Building Cladograms Major assumptions : 1. The group of organisms is monophyletic 2. The outgroup (used for comparison) is closely related to, but separate from your group 3. You can tell which character states are homologous or analogous. Building Cladograms Each bifurcation of the branch is based upon the state (presence/absence) of an apomorphic character Cladograms Cladograms are made by determining the sequence of evolution of shared derived characters Rule of Parsimony: The simplest explanation is the most likely explanation. Cladograms Base change event Cladograms Rule of Parsimony: The simplest explanation is the most likely explanation. Cladograms But not always! Rule of Parsimony: The simplest explanation is the most likely explanation....
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BCladistics - grouping Cladograms Polyphyletic grouping...

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