ch.25 phylogeny and systematics
TRANSCRIPT
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Phylogeny and Systematics
Chapter 25
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• Phylogeny – evolutionary history of a species or group of
species
• Systematics – study of biological diversity in evolutionary
context– Naming and classifying organisms
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How do we know this stuff?
• Evidence of phylogeny– Fossil record– Morphology
• Homology – similarity due to shared ancestor• Analogy – similarity due to convergent evolution
– Molecular evidence (DNA)
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Fossil Record & Geologic Time
• Sedimentary rocks are the richest source of fossils
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Fossil Record: layers of fossils in sedimentary rocks – marks passing of geologic time
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Geologic Time Scale
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Methods to Date Fossils
• Relative Dating – location of fossils in layers of rock– Oldest layers are below newer layers
• Absolute Dating – age given in years– Radiometric dating
• Radioactive isotopes– Carbon, nitrogen, uranium
– L- and D- amino acids
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Radiometric Dating
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Plate Tectonics
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History of Continental Drift
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Mass Extinctions & Biodiversity
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K-T Extinction
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Systematics
Connecting Classification & Phylogeny
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Classification
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Classification & Phylogeny
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CladogramsGrouping species based on similarities
Shared primitive character – shared beyond taxon we are trying to define
Shared derived character – evolutionary novelty unique to a particular clade
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Clade: an ancestral species and all of its decendentcs (monophyletic group)
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Cladistics and Taxonomy
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Modern systematics is shaking up some phylogenetic trees
A phylogenetic tree is a hypothesis
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Timing
• Molecular clocks– Mutations happen
at a steady rate