The process of gas exchange occurs primarily in the lungs in humans and through diffusion in simpler organisms. In humans, oxygen from inhaled air diffuses into the blood through the alveoli, tiny air sacs in the lungs. Simultaneously, carbon dioxide, a waste product of cellular respiration, diffuses from the blood into the alveoli and is exhaled. This exchange happens due to differences in partial pressure of gases. Oxygen-rich blood is then transported to cells, while carbon dioxide is carried back to the lungs for removal. In plants, gas exchange occurs through stomata, where oxygen and carbon dioxide diffuse during respiration and photosynthesis.

Hello aspirant,

Gas exchange in humans occurs mostly in the alveoli and capillaries, where oxygen diffuses from the lungs into the bloodstream and carbon dioxide diffuses from the bloodstream into the lungs.  This exchange, in which carbon dioxide is absorbed and oxygen is released, also occurs between blood and tissues.

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