[8] Phylogeny

[8] Phylogeny - Introduction to Phylogeny Required Reading:...

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Introduction to Phylogeny Required Reading: chapter 4 (Ignore Box 4.1)
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Objectives The basics of phylogenetic trees How phylogenetic trees are constructed. How phylogenies can address questions about evolution.
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Phylogeny Phylogenetics : the study of ancestor descendent relationships. The objective of phylogeneticists is to construct phylogenies Phylogeny : A hypothesis of ancestor descendent relationships. Phylogenetic tree : a graphical summary of a phylogeny
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Phylogeny All life forms are related by common ancestry and descent. The construction of phylogenies provides explanations of the diversity seen in the natural world. Phylogenies can be based on morphological data, physiological data, molecular data or all three. Today, phylogenies are usually constructed using DNA sequence data
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Review: Introduction to Phylogenetic Trees
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Phylogenetic Characters We use characters to construct phylogenies. A character is any attribute of an organism that can provide us with insights into history (shared ancestry). In molecular phylogenies, characters are typically nucleotide positions in a gene sequence, and each position can possess four CHARACTER STATES : A,C, G, or T
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Cladisitc Character State Definitions Plesiomorphy: refers to the ancestral character state Apomorphy : a different character state than the common ancestor, or DERIVED STATE Synapomorphy : a derived character state (apomorphy) that is SHARED by two or more taxa due to inheritance from a common ancestor: these character states are phylogenetically informative using the parsimony or cladistic criterion Autapomorphy : a uniquely derived character state
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Character States After Page and Holmes 1998 we will return to this
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Figure 4.2, pg.113 More Synapomorphies
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Examples of Synapomorphies Figure 4.3, pg. 114 synapomorphies identify monophyletic groups
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[8] Phylogeny - Introduction to Phylogeny Required Reading:...

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