Respuesta :
The appearance of oxygen-producing organisms.
- The appearance of free oxygen in Earth's atmosphere led to the Great Oxidation Event.
- This was triggered by cyanobacteria producing oxygen that was used by multicellular forms as early as 2.3 billion years ago.
What are cyanobacteria?
- Cyanobacteria are aquatic and photosynthetic, that is, they live in the water, and can manufacture their own food.
- Because they are bacteria, they are quite small and usually unicellular, though they often grow in colonies large enough to see.
- Cyanobacteria are responsible for the Earth's transition from a carbon dioxide-rich atmosphere to the present relatively oxygen rich atmosphere as a consequence of oxygenic photosynthesis.
To know more about multicellular here
https://brainly.com/question/11495349
#SPJ3
