BIS 2C Lecture Notes - Lecture 1: Tree Model, Speciation
27 Apr 2018
School
Department
Course
Week1
Lect1 Tree…
Tree of Life
Tree of life: refers to concept that all organisms are related through
shared ancestry or Phylogeny
Can be represented by branching tree - model of genealogy
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Phylogeny is evolutionary history of an organism
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4 billion year history
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Phylogenetic trees allow us to understand and trace historical changes in
morphology, geographical distributions, and other features
Also reveals surprising relationships
Dinos aren’t extinct b/c birds are descendants of dinosaurs
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Reveals convergent evolutions
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Shows/predicts similarities and differences
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Speciation is the process by which one species gives rise to two
descendant species
Phylogenies are results of multiple speciation events
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Forms of Phylogenetic Trees
Can branch with root on the left
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Can branch with root at the bottom
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Terms of Phylogenetic Tree Diagrams
Internal node: node with closest ancestor for taxa coming after it
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Root node: ultimate common ancestor on the tree
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Terminal taxa: last defined taxa (tips)
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Type of Phylogenetic Trees
Cladograms: shows the relation among a group of species or organisms,
but doesn’t really show evolution because doesn’t show how ancestors are
related to descendants
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Phylograms: branches give reading of the amount of evolutionary
changes that have occurred
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Chronograms: branch length give reading to the time between the
changes
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Intro to the Tree of Life (1)
Monday, January 8, 2018
9:22 AM
