Geological Time Scale Scientific Theory of Earth and Lifes History

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Geological Time Scale Scientific Theory of Earth
and Lifes History

• Chapter 14-1
• Chapter 14-2 Optional Reading

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Basis of Geological Time Scale

• Scientific Theory of sequential order of events
  in earths history
• Estimated age of earth - 4.6 BYA
• Broken into Major Eras, each Era broken into
  periods

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How do we know age of fossils, earth and
environmental changes?

• Geological studies rock patterns, tectonic
  plates, volcanic activity, banding patterns on
  rock chemistry of atm.
• Radiometric dating decay of radioactive
  elements begins at death and has measurable rate
  over time
• Relative dating fossil location older
  deeper index fossils
• Continental Drift EX Pangea
• Types of fossils lead to speculation of climate,
  ecosystem

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Basis of Geological Time Scale

• Earths environment has changed drastically over
  time
• ESTIMATED 99.9 OF ALL ONCE LIVING THINGS ARE
  EXTINCT!
• Organisms that are best fit (adapted) will
  survive those that arent ? extinct
• Mutations bring more variation in phenotypes
  which may or may not be better fit for
  environment
• Due to these environmental changes and struggle
  for existence, orgs may become extinct
• Fascinating fact we are currently in the
  LARGEST MASS EXTINCTION IN HISTORY!

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Banding Shows Oxygen Introduction into Earths
Atmosphere cyanobacteria (Precambrian)
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How do we know what ancestry?

• Comparative Morphology homologous structures
• Biochemistry DNA/RNA amino acids
• Comparative Embryology similar developmental
  phases
• ALL vertebrates tail, gill slits!

Fossil Snake Pelvis with Legs Snake ancestor?