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BIO 1M03 - chap 27.docx

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School
McMaster University
Department
Biology
Course
BIOLOGY 1M03
Professor
Ben J Evans
Semester
Summer

Description
BIO 1M03CHAPTER 27 271 The evolutionary history for a group of organisms is called their phylogeny which are summarized thru a phylogenetic tree that shows ancestordescendant relationships each branch represents a population thru time two branches can separate at a node which shows an ancestral group split into 2 descendant groups the ends of the tree have tips at which a living group today or extinct group is shown Closer together on a tree means more shared characteristics there are two strategies used to estimate trees 1 The Phenetic Approachinvolves computing an overall genetic distance between populations This will summarize the similar gene sequences A computer will examine several of these and place trees2 The Cladistic Approachbased on the realization that relationships can be reconstructed by analysing derived characteristics synapomorphies which represent traits that specific groups of species have that no other species do Issues arise when considering if two species have fur not bc they evolved from a common ancestor but bc they evolved separately Homology occurs when traits are similar due to shared ancestryHomoplasy is when traits are similar for other reasonsichthyosaur VS
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