Answer - Cyanobacteria aka Algae that contributed in creating O2 for the atmosphere as a byproduct thru Photosynthetic.
Reason - Of course Algae make up mainly the whole world in waters and they do photosynthesis to give off oxygen in the atmosphere.
The answer is it provides us with vitamins. Hope this helps.
The Characteristics of life are growth, reproduction, homeostasis, sense and respond to stimuli, obtain and use energy, made of cells, adapt and evolve.
A plant cell is rectangular, while an animal cell is circular.