Final answer:
A closed circulatory system involves blood flowing in closed vessels, separate from interstitial fluid, enabling efficient nutrient and waste transport, found in most vertebrates and some invertebrates like the earthworm.
Step-by-step explanation:
A closed circulatory system is characterized by blood flowing within a network of blood vessels that are completely separated from the body’s interstitial fluid. This system ensures that blood flows in a controlled and unidirectional manner from the heart, throughout the body along a systemic route, and then back to the heart. In such a system, nutrients and waste products are transported efficiently. Moreover, animals like earthworms, most vertebrates, and some invertebrates possess a closed circulatory system. Vertebrates such as fish have a two-chambered heart, amphibians and reptiles have a three-chambered heart with little mixing of blood, and mammals and birds boast a four-chambered heart with double circulation, which is highly efficient.