Gas exchange is the process by which oxygen and carbon dioxide are exchanged between the body and the environment. In humans and many animals, this occurs primarily in the lungs, where oxygen from inhaled air enters the bloodstream, and carbon dioxide, a waste product of metabolism, is expelled from the blood into the air to be exhaled. In plants, gas exchange takes place through small openings called stomata on leaves. During photosynthesis, plants take in carbon dioxide and release oxygen, contributing to the balance of gases in the atmosphere. This process is essential for both plant and animal life on Earth.