the respiratory system performs respiration
respiratory_system is not system. lower_respiratory_tract is not respiratory_tract. respiratory_system is system. respiratory_system is organ_system. respiratory_system is not organ_system. air_respiration is physiological_function. cetacean_respiratory_tract is not respiratory_tract. air_respiration is respiration. air_respiration is not respiration. air_respiration is not physiological_function.