Ch22_Lecture-Spr11

Ch22_Lecture-Spr11 - 22 Reconstructing and Using...

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22 Reconstructing and Using Phylogenies
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22 Reconstructing and Using Phylogenies • 22.1 What Is Phylogeny? • 22.2 How Are Phylogenetic Trees Constructed? • 22.3 How Do Biologists Use Phylogenetic Trees? • 22.4 How Does Phylogeny Relate to Classification?
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22.1 Phylogenetic Trees Systematics Scientific study of the diversity of organisms, Reveals evolutionary relationships between organisms. Taxonomy Subdivision of systematics Theory and practice of classifying organisms.
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22.1 What Is Phylogeny? A phylogeny is a hypothesis Proposed by systematist Describes evolutionary history of relationships among organisms from their common ancestor A phylogenetic tree (or cladogram ) represents that history A clade is a branch of phylogentic tree from single common ancestor
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Reconstructing and Using Phylogenies A lineage is represented as branching tree Each split or node represents point at which lineages diverged The common ancestor of all organisms in tree is the root To reconstruct phylogenetic tree, evolutionary changes in the traits of organisms are analyzed
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22.1 What Is Phylogeny? The timing of divergences is shown by the position of nodes on a time or divergence axis Lineages can be rotated around nodes; the vertical order of taxa is largely arbitrary These two cladograms are the same
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Phylogenetic Trees A taxon (plural taxa ) is any group of species that we designate (e.g., vertebrates, Homo , Animalia) A taxon that consists of all descendents of a single common ancestor is called a clade
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Figure 22.3 Clades Represent All the Descendants of a Common Ancestor
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22.1 What Is Phylogeny? Two species that are each other’s closest relatives are sister species Two clades that are each other’s closest relatives are sister clades Phylogenetic trees were originally used in systematics (study of biodiversity); but are now used in nearly all fields of biology
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22.1 What Is Phylogeny? One of the greatest unifying concepts in biology is that all life is connected through evolutionary history The ―Tree of Life‖ is complete, 4-billion- year history of life Knowledge of evolutionary relationships is essential for making comparisons in understanding all levels of biology http://www.ecplanet.com/pic/2006/04/1145173301/treeoflife_haeckel.jpg A modern tree of life from the European Molecular Biology Laboratory (left), and Haeckel’s tree, circa 1879 http://www.scienceinschool.org/repository/images/issue2tree2_large.jpg
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http://www.scienceinschool.org/repository/images/issue2tree2_large.jpg Phylogenetic Trees
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22.1 What Is Phylogeny? Phylogenists try to determine traits that differ within a group of interest (taxon) Then hypothesize when and why traits evolved Often, we wish to know how the trait was influenced by environmental conditions or selection pressures http://taggart.glg.msu.edu/isb200/BISTOND.JPG
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22.1 What Is Phylogeny? Traits inherited from an
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This note was uploaded on 06/06/2011 for the course BSC 2011 taught by Professor Presley during the Spring '11 term at FAU.

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Ch22_Lecture-Spr11 - 22 Reconstructing and Using...

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