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Evolution- Change in life forms over time

Evolution- Change in life forms over time. Why do things change? How do they change?. Estimated age of earth-4.6 Billion years 4 geologic eras Precambrian Paleozoic Mesozoic Cenozoic episodes of mass extinction separates eras. At the beginning

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Evolution- Change in life forms over time

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  1. Evolution- Change in life forms over time Why do things change? How do they change?

  2. Estimated age of earth-4.6 Billion years 4 geologic eras • Precambrian • Paleozoic • Mesozoic • Cenozoic episodes of mass extinction separates eras

  3. At the beginning • Hot, lots of volcanic activity, no free oxygen, but lots of water vapor. • 3.9 Billion years ago, oceans formed • 3.5 BYA first fossil evidence of life- photosynthetic bacteria

  4. The history of earth is written in the rocks. • Fossil: evidence of existence preserved in rock • Structure indicates function Oldest fossils found are 3.5 billion years old and are microscopic photosynthetic bacteria

  5. Analyzing the fossil record • Life was incredible diverse • Size, structure, function • Episodes of mass extinction • Episodes of evolutionary explosions

  6. Fossil Formation • Organism dies • Covered with mud, sand- no decay Compression over time = sedimentary rock and fossil Where might fossils be forming today?

  7. Formation of fossils • Casts- minerals fill in • Mold- leaves an empty space • Amber-preserved or frozen • Trace or carbon imprint

  8. Determining the age of a fossil: 2 ways • Relative dating • Absolute dating

  9. 2. Absolute dating • More accurate than relative dating • Uses radioactive decay of isotopes • Isotopesare radioactive natural variations of elements

  10. Examples of Isotopes T1/2 in years • C-14 decays to N14 5730 years • Uranium 235 to Lead 207 700 million • Potassium 40 to Argon 40 1.3 billion • Half life is the time it takes for half (50%) of the isotope to change into new form.

  11. “Parent” compound is C14 • “Daughter “ compound is N14 • T1/2 is 5730 years • Start with 12.5g of C14 and 187.5 g of N14. How old is your fossil?

  12. Carbon 14 is used for fossils < 50,000 years old • Potassium-40 for older specimens

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