Organisms accordig to their respiration type, and the steps they use to obtain energy:
Aerobic - human. They get their energy from oxidation of food molecules in the presence of oxygen. The oxidation is complete, that is, food molecules are transformed to carbon dioxide (CO2). Oxygen is a critical component that provides electrons to key molecules in metabolic energy generation.
Anaerobic - sulfur bacteria. Anaerobic organisms oxide different compounds (like CO2) without oxygen. Yet, they use other molecules to provide electrons, like hydrogen.
Fermentation - yeasts. Fermentation is a type of anaerobic organism, that is, it happens without oxygen. In fermentation, food molecules oxydation does not happen completely, that is, instead of producing CO2, they produce other waste molecules, like alcohol.