A new study reveals that the aerobic nitrogen cycle in the ocean may have occurred about 100 million years before oxygen began to significantly accumulate in the atmosphere, based on nitrogen isotope ...

The process is called extracellular respiration, which mimics how batteries discharge electric current -- allowing bacteria to thrive without oxygen.

This process requires specialized organs such as the lungs or gills. This oxygen is used for cellular respiration and metabolism, a byproduct of which is carbon dioxide.