The oxygen component would have been smaller.
Explanation:
Photosynthetic plants / organisms evolve oxygen gas as a by-product of the process of photosynthesis. Therefore since their evolution beginning approximately 3.4 billion years ago, the atmosphere, which was once dominated by carbon dioxide, began to fill with oxygen. This period is referred to as the Great Oxygenation Event because it is also responsible for the decline of anaerobes.
Learn More:
For more on the Great Oxygenation Event check out;
https://brainly.com/question/11255683
https://brainly.com/question/13625159
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