Which two systems in animals are important for respiration?

The two systems in animals that are important for respiration are the respiratory system and the circulatory system. The respiratory system, which includes organs such as the lungs or gills, facilitates the exchange of oxygen and carbon dioxide between the organism and its environment. The circulatory system transports oxygen-rich blood from the respiratory system to the body's tissues while carrying carbon dioxide back to the respiratory system for exhalation. Together, these systems ensure efficient gas exchange and oxygen delivery throughout the body.