Final answer:
Fishes have a single circuit in their circulatory system and a two-chambered heart. The single circuit includes gill circulation for oxygenation and systemic circulation to deliver oxygen to the body.
Step-by-step explanation:
The circulatory system of most fishes is composed of a single circuit for blood flow. Fish possess a two-chambered heart, which includes one atrium and one ventricle. Blood flows from the heart to the gills where it is oxygenated during gill circulation, then it circulates through the rest of the body delivering oxygen before returning to the heart, which is known as systemic circulation. Unlike amphibians, reptiles, mammals, and birds that have double circulatory systems with separate pulmonary and systemic circuits, the single circulatory system in fish limits the amount of oxygen that tissues can receive, affecting the metabolic capacity of these aquatic creatures.