Question

list two major ways the earth's atmosphere was different 3 billion years agi before the advent of photosynthesis

Answer 1

• It was a weakly reducing atmosphere
• It was hotter

Explanation:

The primordial earth’s atmosphere was mainly composed of carbon dioxide and methane. These are greenhouse gases that kept the temperatures of the atmosphere high because they trap infrared radiation that reflects off the earth's surface. These gases also made the atmosphere a reducing atmosphere due to the absence of oxygen. The most likely source of carbon dioxide was frequent volcanoes at the time and the methane from early anaerobic microbes.

The atmosphere changed when photosynthetic organisms evolved and caused the Great Oxygenation Event because they evolved oxygen.

Learn More:

For more on Great Oxygenation Event;

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