Summary of Major Events in the Evolution of Life

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Summary of Major Events in the Evolution of Life
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18 Billion Years Ago

• BIG BANG
• The universe began with the so called Big Bang,
  an event about 13 - 18 billion years ago, during
  which all the matter in the universe was
  scattered in enormous explosion.

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4.6 Billion Years Ago

• Big Rock Earth Forms
• The first atmosphere began to form from CO2, CO,
  water vapor, N2, H2S, and small traces of CH4,
  and NH3.
• Lack of Oxygen.

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3.8 Billion Years Ago

• THE ORIGIN OF LIFE.
• First Prokaryotic Cells Appear.

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3.2 Billion Years Ago

• Autotrophs.
• Little change in atmosphere.

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2.8 Billion Years Ago

• Strong evidence of photosynthetic organisms.
• Oxygen is given off into atmosphere, but still is
  less than 1.

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2.0 Billion Years Ago

• Blue-Green Algae.
• Ozone screen begins to form.

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1.5 Billion Years Ago

• First eukaryotic cells appear.
• 2 oxygen in atmosphere.

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670 Million Years Ago

• Multicellular organisms.
• 7 oxygen in atmosphere.

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550 Million Years Ago

• Shelled Animals.
• Early Land Plants.
• 10 Oxygen in Atmosphere.

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500 Million Years ago

• Fishes.
• Land plants.
• Atmosphere same as today, 20 oxygen.
• Complete ozone screen.

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395 Million Years Ago

• First amphibians.

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321 Million Years Ago

• First reptiles.

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225 million years Ago

• First flowering plants.
• First birds and mammals.

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Mammals
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1 - 2 Million Years Ago

• Human Kind - Homo sapiens.