In order to live, grow, and reproduce, all living things need energy obtained from oxygen. From the simplest of cells to the largest of animals, energy is generated from oxygen in a process called respiration, or breathing. Learn about the definition and characteristics of aerobic respiration, the respiratory organs, the process of photosynthesis in plants, different organisms and their respiratory processes, human respiration, lungs and other organs use in respiration, as well as how humankind has exploited nature’s resources.