Lecture IX - Phylogenetics

Lecture IX - Phylogenetics - Lecture IX - Phylogenetics...

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Lecture IX - Phylogenetics
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Phylogeny From Wikipedia: In biology , phylogenetics ( Greek : phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e.g., species , populations). Also known as phylogenetic systematics , phylogenetics treats a species as a group of lineage-connected individuals over time.
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Tree of Life “The notion that all of life is genetically connected via a vast phylogenetic tree is one of the most romantic notions to come out of science. How wonderful to think of the common ancestor of humans and beetles”. (From the website “The Tree of Life We Project”: http://www.tolweb.org/tree/ phylogeny.html)
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Reconstructing Trees: Cladistics Cladistics is a method of reconstructing evolutionary trees. The basis of a cladistic analysis is data on the characters, or traits, of the organisms in which we are interested
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Cladistics These characters could be anatomical, physiological, behavioral, or genetic The result of a cladistic analysis is a tree, which represents a hypothesis about the relationships among the taxa
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Reconstructing Trees Step by Step Choose the taxa Determine the characters Determine the polarity of characters Group taxa by synapomorphies Work out conflicts Build your tree
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Choose the Taxa Select the taxa, or taxonomic level of classification whose evolutionary relationships interest you. These taxa will be the tips of your tree For example: 20 species of beetle within the same genus the major clades of insects (beetles, flies, moths and butterflies, true bugs, dragonflies, etc.), each taxon includes many species.
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Determine the Characters Determine the characters of interest and determine the character states. For example, using anatomical traits as your characters (number of digits on an appendix) Character states = different anatomical characteristics (one, two, three, etc. digits) Alternately, 10 loci on a genome, Character states would then be different alleles
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Lecture IX - Phylogenetics - Lecture IX - Phylogenetics...

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