Final answer:
A closed circulatory system features blood confined within vessels separated from body fluids, with varying numbers of heart chambers across animal classes and efficient nutrient and waste transport.
Step-by-step explanation:
A closed circulatory system is characterized by the blood being entirely contained within blood vessels, which separates it from the interstitial fluid of the body. In such systems, the heart pumps blood through the vessels, offering a more structured and efficient means of circulating nutrients and waste. Different classes of animals exhibit variations in heart chamber numbers, with fish typically having a two-chambered heart, amphibians, and reptiles usually having a three-chambered heart, and mammals and birds having a four-chambered heart, which supports double circulation.