Answer:
"Photosynethic bacteria (Cyanobacteria)" was first responsible for changing the formerly poisonous atmosphere to an oxygen-rich atmosphere, as we have today
Explanation:
The cyanobacteria are photosynthetic bacteria that are oxygenic. They extract energy from the sun, take up carbon dioxide and release oxygen. Unlike plants and algae, cyanobacteria comprise chlorophyll, and by carbon fixation transform carbon dioxide into sugar.
Cyanobacteria are prokaryotic species, unlike eukaryotic plants and algae. A phylum composed of free-living bacteria and endosymbiotic plastids (a Gloeomargarita sister group found in certain eukaryotes) is called as Cyanophyta or Cyanobacteria. These also contain multiple yellowish carotenoids, the blue phycobilin pigment and, in certain organisms, the red phycoerythrin pigment.
