Early Earth's Atmosphere and Evolution of Life

• Formation of first prokaryotic life forms

  Occurred 3.5 billion years ago
• First prokaryotic life forms

  Released oxygen into the atmosphere through photosynthesis
• Formation of oxygen on earth


  Global release of oxygen known as the Great Oxygenation
• Complex life forms


  Formed around 540 million years ago
• Organism changes with geosphere and atmosphere

  Organisms change as the earth's geosphere and atmosphere change
• Difficulty in finding records of early earth


  Incomplete fossil records make it hard to find early records
• Additional evidence of early earth's atmosphere


  Tiny bubbles of gas trapped in rocks from early earth
• Evidence of early earth's conditions

  Old volcanoes in Iceland made of materials from early earth
• Gasses in early earth's atmosphere

  Carbon dioxide, helium, hydrogen gas, methane, ammonia, and water vapor
• Appearance of most life forms

  Around 540 million years ago
• Earth's formation

  Occurred about 4.6 billion years ago
• Changes in geosphere and atmosphere


  Cause changes in the biosphere
• Atmosphere


  Layer of gases surrounding the earth
• Biosphere


  Zone of life on earth
• Geosphere


  Earth's solid, rocky outer layer
• Nitrogen


  Abundant gas in early earth's atmosphere that has remained relatively unchanged
• Environmental conditions

  Early earth's atmosphere did not allow life forms due to toxic gases
• Cyanobacteria


  Type of bacteria involved in the Great Oxygenation
• Great Oxygenation


  Event 2.3 billion years ago that allowed for more complex life forms
• Photosynthesis


  Key process that changed early earth's atmosphere for complex life forms