The Smithsonian Assignment - The Smithsonian Assignment...

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The Smithsonian  Assignment Sabiha Sungur     11/13/2011 Early Atmosphere 1. Small amounts of free oxygen 2. Oxygen was a threat to organisms accustomed to living without it. They slowly died off, leaving the ones who could resist oxygen to survive and finally depend on it for life. Single-celled blue-green algae released enough oxygen into the air. Oxygen is highly demanded by organisms today, which wasn’t as necessary in early life forms. 3. Origin and spread of organisms capable of photosynthesis. 4. Stromalites: laminated, mound-like structures that generally form in shallow water through the growth of microscopic blue-green algae and bacteria. 5. Evidence of communities of ancient microorganisms. 6. Screens out harmful ultraviolet radiation from the sun. Formed only after oxygen from photosynthesis occurred. The ozone today forms by the ultraviolet rays reacting on oxygen. 7.
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The Smithsonian Assignment - The Smithsonian Assignment...

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