when you inhale ( breathe in ), air enters your lungs and oxygen from the air move from your lungs to your blood. at the same time carbon dioxide moves from your blood to the lungs and is exhaled ( breathe out ). this process is called gas exchange and is essential to life
Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.