Final answer:
Gills and air sacs differ in terms of their location in the body and their function in respiration.
Step-by-step explanation:
Gills and air sacs differ in terms of their location in the body and their function in respiration. Gills are specialized organs found in aquatic animals, such as fish, that extract oxygen from water. They are typically located on either side of the fish's head and are used for oxygen exchange. On the other hand, air sacs are found in birds and play a role in their unique breathing system. Air sacs are located throughout the bird's body, and they allow for unidirectional flow of air through the respiratory system, which is important for efficient gas exchange during flight.