Hunny You Should Know This Answer Stop Cheating Its In Your Book
oxygen
Oxygen was added to Earth's atmosphere through the process of photosynthesis by early photosynthetic organisms like cyanobacteria. These organisms released oxygen as a byproduct, which accumulated over millions of years and eventually led to the oxygen-rich atmosphere we have today.
The earths atmosphere is made up of 78% nitrogen and 21% oxygen
Scientist theorize that bacteria with chlorophyll in them slowly but surely began to multiply. And as they did, they photosynthesized enough to create an entire atmosphere. (as you know oxygen is a byproduct of photosynthesis)
97%
no
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.
Oxygen gas
Free oxygen
Plants
oxygen
Nitrogen and oxygen,