What is the primary function of the respiratory system in animals?

The primary function of the respiratory system in animals is to supply oxygen and remove carbon dioxide. This process is essential for aerobic respiration, which is the metabolic pathway that produces energy in the form of ATP by utilizing oxygen to break down glucose. As animals consume oxygen during this process, carbon dioxide, a byproduct, accumulates in the body and must be expelled to maintain pH balance and prevent respiratory acidosis.

The respiratory system’s structures, including the lungs and airways, facilitate this gas exchange. In mammals, for example, oxygen is absorbed into the bloodstream in the alveoli, microscopic air sacs in the lungs, while carbon dioxide is expelled when the animal exhales. This vital exchange supports cellular respiration, enabling organisms to sustain life and carry out physiological processes.

The other options do not encompass the main role of the respiratory system. While aspects like temperature regulation and nutrient processing are important for overall bodily functions, they are primarily handled by other systems such as the circulatory and digestive systems. Therefore, the focus on gas exchange underscores the respiratory system's crucial role in maintaining homeostasis in the body.