The mechanism of gaseous exchange in living organisms is essentially by

The mechanism of gaseous exchange in living organisms is essentially by diffusion. This is the process by which gases move from an area of high concentration to an area of low concentration. In the case of respiration, oxygen moves from the air outside the body into the lungs, where it diffuses into the bloodstream and is transported to cells throughout the body. At the same time, carbon dioxide, a waste product of metabolism, diffuses out of cells and into the bloodstream, which then carries it back to the lungs to be exhaled. Breathing, which involves inhalation and exhalation, is the process by which air is moved in and out of the lungs to facilitate gas exchange by diffusion.