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Evolution and Change

Evolution and Change. Chapter Fourteen: Earth and Life History. 14.1 Evidence from Rocks 14.2 How Earth Changes 14.3 Natural Selection. Investigation 14B. Interpreting the Fossil Record. How do scientists analyze the fossil record?. 14.3 Life History.

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Evolution and Change

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  1. Evolution and Change

  2. Chapter Fourteen: Earth and LifeHistory • 14.1 Evidence from Rocks • 14.2 How Earth Changes • 14.3 Natural Selection

  3. Investigation 14B Interpreting the Fossil Record • How do scientists analyze the fossil record?

  4. 14.3 Life History • Scientists have developed a model of the history of life on Earth called the geologic time scale. • Paleontologists divide the geologic time scale into blocks of time called erasand periods.

  5. 14.3 Life History • The Precambrian era lasted from Earth’s formation 4.6 billion years ago until 542 million years ago (mya). • The first cells appeared in the Precambrian era.

  6. 14.3 Life History • The Paleozoic era lasted from 542 to 251 mya. • Paleozoic is a Greek word meaning “ancient life.” • Rocks dated from the Paleozoic era contain fossils of trilobites, snails, clams, and corals.

  7. 14.3 Life History • The Mesozoic era lasted from 251 to 65 mya. (Mesozoic is a Greek word meaning “middle life.”) • This era is often called the Age of Reptiles.

  8. 14.3 Life History • The Cenozoic era began 65 mya and is still going on. • Cenozoic means “recent life.” • Fossils from the Cenozoic era are closest to Earth’s surface, making them easier to find.

  9. 14.3 Mass extinctions • Mass extinctionsare periods of large-scale extinction. • They seem to be part of the evolutionary process because after each, new life forms emerge. Asteroids may have played a part in previous mass extinctions.

  10. 14.3 Absolute dating • Absolute datingis a method of estimating the age of a fossil in years. • Absolute dating requires the use of a natural “clock.” • That clock is the radioactive decayof certain naturally-occurring elements like carbon.

  11. 14.3 Absolute dating • Half-lifeis the amount of time it takes for half of the unstable atoms in a sample to decay. • In a sample of uranium-238, it takes 4.5 billion years for half of the uranium atoms to transform into lead atoms.

  12. Paleontology Connection Mass Extinctions: Devastation and Opportunity • Something drastic happened about 65 million years ago—the fossil evidence is clear.

  13. Activity Radioactivity and Half-Life • Scientists use absolute dating to estimate the age of a fossil in years. • Absolute dating uses the decay of radioactive elements as a natural “clock.”

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