What was the first organisms to breath out oxygen into the sea in the world’s history?

Question: What was the first organisms to breath out oxygen into the sea in the world's history?

Asked by conn207 to Antonia, Douglas, Hugh, Matt, Tom on 14 Jun 2010 in Categories: General.
- Matthew Hurley answered on 13 Jun 2010:
  
  This would have to be cyanobacteria – they were around the first. They’re great – they also glow in the dark!
- Antonia Hamilton answered on 14 Jun 2010:
  
  Not many things breath out oxygen. Plants produce oxygen by photosynthesis, and animals breath in oxygen and breath out carbon-dioxide. do you mean the first plant in the ocean? I don’t think anyone knows. And their might have been some algae or something similar producing oxygen even earlier.

Question: What was the first organisms to breath out oxygen into the sea in the world's history?