Lecture 16 PDF
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University of Maryland, College Park
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This document discusses homology and analogy in evolutionary biology. It explains how similarities can arise through independent evolution (analogy) or shared ancestry (homology). The document also covers methods to reconstruct evolutionary relationships.
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Homology vs. analogy Analogous traits ○ Similarities that are independently derived ○ Convergent evolution ○ Don’t use in cladograms ○ Common function but not evolutionary origin Homologous traits ○ Similar since they have a shared common ancestry ○ use in cladograms and phylogenies Darwins “Great t...
Homology vs. analogy Analogous traits ○ Similarities that are independently derived ○ Convergent evolution ○ Don’t use in cladograms ○ Common function but not evolutionary origin Homologous traits ○ Similar since they have a shared common ancestry ○ use in cladograms and phylogenies Darwins “Great tree of Life” Organisms united by shared ancestry Can reconstruct tree Reconstruct Tree 1. Analysis of fossils ○ Pros: Direct ○ Cons: Fragmentary, hard to interpret 2. Phylogenetic Analysis ○ Compare similarities of organisms ○ Construct cladograms and phylogenies ◆ Phylogenies ◇ Branch and connection on tree of life ◇ Produced by two evolutionary events Speciation Original of new characteristic Cladograms Branch diagram depicting estimate of phylogeny Determine evolutionary relationships between living organisms based on shared derived similarity Clade ○ Grouping that includes a common ancestor and all the descendants of that ancestor Monophyletic Shared derived Trait = synapomorphy Single origin/ancestor and all descendant species grouped together Close relationship Monophyletic group = clade Polyphyletic Convergent similarity = analogous Independent origins Not close relationship No common ancestor Paraphyletic Single origin/ancestor species ○ Includes some, not all descendants No close relationship Not used in cladistics Trait Bar Not mutation Indicates when mutation spread through population and xes All descendants have it Phylogenetic analysis Goal = Monophyletic groups ○ Accurate relationships Willi Hennig ○ 2 principal techniques for reconstructing phylogeny ◆ Outgroup analysis ◆ Parisomy = Methods to distinguish derived from primitive similarity ◇ Cladogram = fewest evolutionary changes is preferred Cladogram vs. Phylogenetic trees Cladogram = hypothesis of evolutionary history, Is not evolutionary tree Phylogenetic = True evolutionary history, Is evolutionary tree
