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ATMOSPHERE
Lesson 5 - Page 2

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The volcanoes produced a change on Earth. The Sunís 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 Earthís atmosphere as more and more photosynthetic organisms evolved.


  


Can life start here?

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