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Summary of Major Events in the Evolution of Life. 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. 4.6 Billion Years Ago.
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18 Billion Years Ago • BIG BANG • The universe began with the so called Big Bang, an event about13 - 18 billionyears ago, during which all the matter in the universe was scattered in enormous explosion.
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.
3.8 Billion Years Ago • THE ORIGIN OF LIFE. • First Prokaryotic Cells Appear.
3.2 Billion Years Ago • Autotrophs. • Little change in atmosphere.
2.8 Billion Years Ago • Strong evidence of photosynthetic organisms. • Oxygen is given off into atmosphere, but still is less than 1%.
2.0 Billion Years Ago • Blue-Green Algae. • Ozone screen begins to form.
1.5 Billion Years Ago • First eukaryotic cells appear. • 2% oxygen in atmosphere.
670 Million Years Ago • Multicellular organisms. • 7% oxygen in atmosphere.
550 Million Years Ago • Shelled Animals. • Early Land Plants. • 10 % Oxygen in Atmosphere.
500 Million Years ago • Fishes. • Land plants. • Atmosphere same as today, 20% oxygen. • Complete ozone screen.
395 Million Years Ago • First amphibians.
321 Million Years Ago • First reptiles.
225 million years Ago • First flowering plants. • First birds and mammals.
1 - 2 Million Years Ago • Human Kind - Homo sapiens.