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The volcanoes produced a change on Earth. The Sun’s radiation probably
was able to begin chemically altering the products of the volcanoes.
Ultraviolet rays are noted for breaking up water molecules to produce
oxygen and ozone. Enough ozone could have created a protective shield in
the forming atmosphere. The atmosphere, hydrosphere, and lithosphere
were all becoming suitable for life.
Life had a profound effect on the atmosphere. The new little critters
evolved to make use of the gases available and give off other gases. It
seems that organisms changed the atmosphere as they evolved through
time.
Life evolved on Earth by at least 3.8 billion years ago. By about 3.5
billion years ago, primitive organisms evolved that could perform
photosynthesis. Photosynthesis is a chemical reaction in which
plants take carbon dioxide (CO2) and water and convert them
into energy using sunlight. The main byproduct of this reaction is
oxygen (O2). Oxygen thus accumulated in the Earth’s
atmosphere as more and more photosynthetic organisms evolved.
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