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Phylogeny and Systematics

Phylogeny and Systematics. … or ‘Who’s Tribe Are You From?’. Fossils are the source for identifying and classifying extinct species. Relative Dating and Absolute Dating are the two methods of dating fossils on a geologic time scale. Fossils. Relative Dating vs. Absolute Dating.

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Phylogeny and Systematics

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  1. Phylogeny and Systematics … or ‘Who’s Tribe Are You From?’

  2. Fossils are the source for identifying and classifying extinct species. Relative Dating and Absolute Dating are the two methods of dating fossils on a geologic time scale. Fossils

  3. Relative Dating vs. Absolute Dating • Layers of sediments trap fossils in rock. Each stratum of rock can be identified by index fossils, thus around the world fossils can be given an aprox era based upon geological studies. • Absolute dating is not exact however it can give a range of time rather then an era. Radioactive isotopes are used to date fossils or rocks.

  4. Radiometric Dating = Absolute Dating • Fossils contain isotopes of elements accumulated during the fossils life. • Ex. Carbon-14 decays to Nitrogen-14 • Each isotope has a half-life or the number of years for 50% of the original example to decay. • Half-life is typically unaffected by temp, pressure, or other environmental factors.

  5. Examples of RD • Carbon-14 half-life = 5730 years • Organic matter • Uranium-238 half-life = 4.5 billion years • Decays to Lead-206 (rocks) • Potasium-40 half-life = 1.251 billion years • Decays to Argon-40 (rocks) • Uranium-235 half-life = .704 billion years • Decays to Lead-207 (rocks)

  6. More additions to Geologic Time • Continental Drift • Lots of impact on speciation, little or no geographic isolation. • Lower sea levels • Decreased coast line = more competition • Increased interior lands = harsher climates • Deeper seas = decreased marine habitat • Huge environmental impact.

  7. Mass extinctions show long periods of life punctuated by large turnovers of species. Mass Extinction opens the door for many new species to fill in free niches. Mass Extinction                                              <>

  8. Classifying Organisms • Linnaeus developed the classification system we use today (Binomial) • Genus and species. • A hierarchial classification organizes organisms in groups. • Useful to organize groups of organisms. • Ex. chordates are in the phylum Cordata.

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