Evolution Change in life forms over time

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Evolution- Change in life forms over time

• Why do things change?
• How do they change?

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

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• 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

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• 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
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Analyzing the fossil record

• Life was incredible diverse
• Size, structure, function
• Episodes of mass extinction
• Episodes of evolutionary explosions

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• Fossil Formation
• Organism dies
• Covered with mud, sand- no decay
• Compression over time sedimentary rock and
  fossil

Where might fossils be forming today?
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• Formation of fossils
• Casts- minerals fill in
• Mold- leaves an empty space
• Amber-preserved or frozen
• Trace or carbon imprint

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Determining the age of a fossil 2 ways

• Relative dating
• Absolute dating

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• Relative dating
• Fossils in deepest layer are oldest

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

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• 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.

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• 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?

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