Final answer:
The water-vascular system is unique to echinoderms and separate from circulatory systems, which can be open or closed. Closed circulatory systems, found in vertebrates, involve blood contained in vessels, with heart complexity ranging from two to four chambers depending on the organism.
Step-by-step explanation:
The concept of a water-vascular system is particularly relevant in the biology of echinoderms, like sea stars, and is separate from the respiratory and circulatory systems found in vertebrates and many invertebrates. On the other hand, animals with circulatory systems have either a closed circulatory system or an open circulatory system to transport blood or hemolymph throughout the body.
The closed circulatory system is one where the blood is separated from the interstitial fluid and contained within vessels, as seen in vertebrates like fish, amphibians, reptiles, mammals, and birds, with varying complexity of heart chambers to accommodate their physiological needs. For example, fish have a two-chambered heart, while mammals and birds boast a four-chambered heart, enabling efficient double circulation.
Most animals use their circulatory system for important functions like transporting gases, nutrients, and wastes and accommodating the demands of different body sizes and functions through evolution. Simple animals, like sponges, may lack circulatory systems altogether while more complex organisms have evolved closed systems with specialized structures such as hearts and vessels.