Answer:
Carbon dioxide from volcanic activity became a major part of the atmosphere.
Explanation:
It's a stage of the very important Nitrogen cycle. All living things need Nitrogen, without it there is no life.
Answer:
BECAUSE WE DONT KNOW!!!!!!!!!!!!!!!!
Explanation:
The correct answer is - cyanobacteria.
The atmospheric oxygen came from the cyanobacteria. These were one of the earliest living organisms on Earth. The cyanobacteria was using photosynthesis in order to create its own food. The photosynthesis process requires sunlight, carbon dioxide, water, and oxygen. The oxygen is mostly released as a waste product from the process of photosynthesis, thus the cyanobacteria were literally releasing oxygen that was ending up into the atmosphere. As more and more cyanobacteria there were across the planet, more and more oxygen they were releasing into the atmosphere, slowly changing the composition of the atmosphere, and setting the basis of it as we know it now.
