Final answer:
In amniotes, such as reptiles, birds, and mammals, blood flows in two circuits: pulmonary circulation and systemic circulation. Amphibians have a three-chambered heart with some mixing of oxygenated and deoxygenated blood, and an additional circulation route called pulmocutaneous circulation.
Step-by-step explanation:
In amniotes, such as reptiles, birds, and mammals, blood flow is directed in two circuits: pulmonary circulation and systemic circulation. Pulmonary circulation involves the flow of blood from the heart to the lungs and back, while systemic circulation delivers oxygenated blood to the rest of the body. Amniotes have a four-chambered heart that separates oxygenated and deoxygenated blood, resulting in more efficient oxygenation.
In contrast, amphibians have a three-chambered heart with two atria and one ventricle. The ventricle receives blood from both the lungs and the body, leading to some mixing of oxygenated and deoxygenated blood. This reduces the efficiency of oxygenation. Amphibians also have an additional circulation route called pulmocutaneous circulation, where gas exchange occurs through the skin. This allows for some oxygen uptake when amphibians are on land.