Birds and mammals possess a separated right and left side of the heart to ensure efficient oxygen supply and prevent the mixing of oxygenated and deoxygenated blood. This anatomical arrangement supports their high-energy lifestyles, vital for maintaining constant body temperature. The right side pumps deoxygenated blood to the lungs for oxygenation, while the left side pumps oxygenated blood to the rest of the body. This separation enables a more effective circulation system, essential for meeting the elevated metabolic demands associated with warm-blooded animals like birds and mammals, ensuring optimal oxygen delivery for sustaining their high-energy activities.