BIO 2150 Chapter 23 Notes I Phylogeny relatedness relatedness A Phylogeny attempts to classify organisms based on their genetic B Phylogenetic Trees a way of diagrammatically expressing this 1 Branches on these trees represent species or populations 2 Nodes on these trees represent speciation events 3 Clade a group that includes a common ancestor and all its decedents 4 Monophyletic Group a group of branches on the tree that includes a common ancestor and all the decedents 5 Paraphyletic group a group of branches on the tree that includes a common ancestor and some but not all of its decedents 6 Polyphyletic Group A group of branches on the tree that doesn t include a common ancestor II Assembling a Phylogenetic Tree A These trees show a comparison of morphological traits 1 Homology indicates a decent from a common ancestor 2 Analogy evolves independently and has no common ancestor 3 Ancestral came from a common ancestor 4 Derived evolves independently B Synapomorphy a trait derived homologous trait III Other Way to Assemble Trees A DNA sequences or amino acids change in proteins 1 Fewer changes between species reflect a close relationship 2 This is useful for analyzing relationships IV Extinct Species and Time Scales A Fossils Preserved remnants of extinct animals or their activities 1 Trace fossil evidence of prehistoric life B Absolute age of fossils is found using radiometric dating C The fossil record can identify 1 The first appearance of a particular species or clade 2 The last appearance of extinct species or clade 3 The existence of intermediate forms or missing links
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