Final answer:
Animal respiratory surfaces need to be large, moist, thin, and have a good blood supply for efficient gas exchange, such as the alveoli in mammalian lungs.
Step-by-step explanation:
The four main characteristics of an animal's respiratory surface are that it needs to be large, moist, and thin with a good blood supply to efficiently facilitate the diffusion of gases. These attributes ensure that oxygen can be absorbed and carbon dioxide can be released effectively. A large surface area, such as that provided by the many alveoli in mammalian lungs, increases the amount of gas that can be exchanged at one time.
Moisture is necessary because gases must dissolve in liquid to diffuse through cell membranes. A thin respiratory surface shortens the distance gases must travel between the air and blood, making diffusion happen more quickly. Lastly, a good blood supply enables the transport of respiratory gases to and from the tissues of the body.