Final answer:
The three-chambered heart system found in amphibians and some reptiles offers double circulation with reduced blood mixing, enabling high-pressure blood flow through the body and lungs. It is more efficient than the two-chambered system but less so than the four-chambered heart system, which is crucial for the high metabolism of mammals and birds.
Step-by-step explanation:
The three-chambered heart system, found in amphibians and some reptiles, offers an intermediate complexity between the two-chambered heart system of fish and the four-chambered heart system of mammals and birds. In a three-chambered heart, there are two atria and one ventricle.
This arrangement allows amphibians to sustain a double circulation, with oxygenated and deoxygenated blood being directed into separate circuits for the body and lungs. The presence of a ridge within the ventricle helps to reduce the mixing of the two blood types, thus improving the efficiency compared to a single circulation system.
One significant advantage is that the three-chambered system can generate high pressure to push blood through the systemic and pulmocutaneous circuits, which is important for gaseous exchange and nutrient delivery.
However, it is less efficient than the four-chambered heart, where oxygenated and deoxygenated blood are fully separated, resulting in a more efficient movement of oxygen and carbon dioxide around the body. The enhancement in circulatory efficiency is particularly necessary for the active lifestyles of warm-blooded mammals and birds.