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oxygen
Hydrogen and helium
It came from primitive organisms early in earth's history. They were the first organisms to use photosynthesis to make food, by using light to convert Carbon dioxide and water into glucose (food) and oxygen. Since oxygen is a waste product of photosynthesis, it was released into the air. As more and more of these organisms multiplied, large amounts of oxygen were released into the air, forming today's atmosphere.
photosynthesis by cyanobacteria
well sir, you see balls are very harry. that is all.
yes
oxygen
oxygen
no
photosynthsis
Photosynthesis by plants
oxygen
Yes
Earth's early atmosphere was primarily composed of carbon dioxide. Early bacteria used carbon dioxide as a source of fuel and as a result produced oxygen.
mostly carbon dioxide with little or no oxygen.
They look at the mineral composition of the rocks. There are some minerals that can only form in the presence of oxygen.
Oxygen Please study this, & don't forget it so you don't have to keep looking up answers .