Respuesta :
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.
Oxygen first began to enter Earth's atmosphere after the appearance of cyanobacteria.
- The ability to generate oxygen via photosynthesis likely first appeared in the ancestors of cyanobacteria.
- These organisms evolved at least 2.45–2.32 billion years ago, and probably as early as 2.7 billion years ago or earlier.
Why cyanobacteria was important for evolution?
- Cyanobacteria carry out oxygen-evolving, plant-like photosynthesis.
- Earth's oxygen-rich atmosphere and the cyanobacteria origin of plastids in plants are the two major evolutionary contributions made by cyanobacteria.
- Certain cyanobacteria are able to carry out nitrogen fixation.
To know more about evolution here
https://brainly.com/question/13492988
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