Download - Phylogeny & Systematics
AP Biology 05/03/23
Chapter 25.Phylogeny & Systematics
An unexpected family tree. What are the evolutionary relationships among a human, a mushroom, and a tulip? Molecular systematics has revealed that—despite appearances—animals, including humans, and fungi, such as mushrooms, are more closely related to each other than either are to plants.
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Building phylogenies Morphological & molecular homologies
similarities based on shared ancestries bone structure DNA sequences
beware of analogous structures convergent evolution
“Homoplasies” marsupial mole
placental mole
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Evaluating molecular homologies Aligning DNA
sequences more bases in
common = more closely related
analyzed by software
beware of molecular homologies
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Orthologous genes
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Common genes:
differences due to
speciation; diverged after a speciation
event
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Paralogous Genes
Common genes; differences due to a duplication event
Examples: next page
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Ortho/Para Genes example:
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Connection between classification & phylogeny
Tracing possible evolutionary relationships between some of the taxa of the order Carnivora, a branch of the class Mammalia.
Building trees
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Illustrating phylogeny Cladograms
patterns of shared characteristics
Classify organisms according to the order in time at which branches arise along a phylogenetic tree
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Illustrating phylogeny Cladograms
patterns of shared characteristics
Shared Primitive Character
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Illustrating phylogeny Cladograms
patterns of shared characteristics
Shared Derived Character
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Parsimony & analogy vs. homology
Phylogenetic trees are hypothesesWhich is the most parsimonious tree?
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Parsimony & analogy vs. homology
Maximum Parsimony
Maximum Liklihood
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Modern Systematics Shaking up some trees!
Crocodiles are now thought to be closer to birds than other reptiles
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Molecular clocksTrace variations in genomes to date evolutionary changes
Rate of change is calculated and then extrapolate back
What does this assume?
HIV-1M samples were collected from patients between early 1980s & late 1990s. The gene evolved at a relatively constant rate. Concluded that HIV-1M strain first infected humans in 1930s.
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Trees: Phylogram (Primates)
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Tree: Phylogram (Giraffe species)
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Tree: Ultrametric
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Universal Tree of Life 3 Domains
Bacteria Eukarya Archaea