respiration science definition

1. The process by which organisms exchange gases, especially oxygen and carbon dioxide, with the environment. In air-breathing vertebrates, respiration takes place in the lungs. In fish and many invertebrates, respiration takes place through the gills. Respiration in green plants occurs during photosynthesis.
2. See cellular respiration.

respiration

During inhalation (top), the diaphragm descends and air fills the lungs. During exhalation (bottom), the diaphragm rises and the lungs expel air.