The American Black Bear exchanges air with oxygen and carbon dioxide. O2 goes through the nasal cavity, larynx, trachea, bronchi, bronchioles, and the alveoli. C02 Is produced once when the oxygen is obtained in the bloodstream. It obtains oxygen though the air. The nasal cavity cleans bacteria in the air. Larynx closes during the breathing. The trachea allows gases to enter and exit. The bronchioles are located in it's lungs, and the exchange of gases occur. Next, in the alveoli oxygen diffuses in the blood.