The document describes the major changes in Earth's atmosphere over time from 4.6 billion years ago to the present. Initially, the atmosphere was dominated by volcanic emissions of gases like carbon dioxide and water vapor. As the planet cooled over billions of years, oceans formed and early life emerged that began processing carbon and sulfur compounds. Around 2.2 billion years ago, photosynthetic organisms produced enough oxygen that it accumulated in the atmosphere, in an event known as the Great Oxygenation Event. The coevolution of life and atmospheric composition led to increasingly complex organisms on Earth.

1. Notes:
Summarize: Five lines to write on
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Key Words and
Questions:
Atmospheric Changes Over Time

2. Primeval
Atmosphere
• 4.6-4.0 Billion Years Ago
• Earth was dominated by volcanoes so the atmosphere
was full of volcanic emissions (water vapor, CO2, sulfur
compounds)

3. Cooling
Period
• 4.0 Billion Years Ago
• Earth’s surface cooled allowing water vapor to condense
forming the oceans

4. Early Life
• 4.0-2.5 Billion Years Ago
• Primitive life arises which begin to process the carbon
and sulfur compounds

5. Great
Oxygenation
Event
• 2.2 Billion Years Ago
• Photosynthetic organisms began to produce enough
oxygen for it to be released into the atmosphere and
build up

6. Coevolution
• The slow evolution of organisms over time due to
abiotic (non-living) or biotic (living) factors
• Ex: the rise in oxygen levels allowed for larger and more
complex life on Earth

7. Historic
Oxygen
Levels

8. Historic
Carbon
Dioxide
Levels