The primary gas produced by respiration is carbon dioxide. During cellular respiration, organisms convert glucose and oxygen into energy (in the form of adenosine triphosphate or ATP), producing carbon dioxide and water as byproducts. This process occurs in the cells of all aerobic organisms, including plants and animals. The carbon dioxide released is then used by plants during photosynthesis, creating a vital cycle that maintains atmospheric balance. Understanding the gas exchange processes is crucial for ecology and environmental science.