Oxygen entered the Earth's atmosphere after the appearance of the Great Oxidation Event (Great Oxygenation Event). The Great Oxidation is the first mass extinction on Earth.
The Great Oxidation lasted 2.4 to 2.0 billion years ago.
Oxygen appeared on Earth thanks to cyanobacteria using photosynthesis.
1.) [Bacteria] are single-celled organisms with no nucleus.
2.) The kingdom [Archaebacteria] is relatively small.
3.) Eubacteria are classified by [shape].
4.) [coccus] are round bacterial cells.
5.) [bacilli] are rod-shaped bacterial cells.
6.) [spirilli] are spiral-shaped bacterial cells.
Answer:approximately 35 phyla;
Explanation:
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