[Campbell Biology P.974] Birds and mammals, as endotherms, require significantly more energy... | Practice Question

Birds and mammals, as endotherms, require significantly more energy than equal-sized ectotherms. How does their double circulatory system support this high energy demand?

  • A: Their four-chambered heart allows for complete separation of oxygen-rich and oxygen-poor blood, maximizing O2 delivery.
  • B: They can vary blood flow to the lungs and body independently, optimizing gas exchange.
  • C: Their circulatory system operates at a lower overall pressure, reducing energy expenditure.
  • D: They primarily rely on the pulmocutaneous circuit for gas exchange, which is more efficient for high metabolic rates.

Explanation

Endotherms like birds and mammals have high metabolic rates requiring substantial oxygen and nutrient delivery. Their four-chambered hearts provide complete separation of oxygen-rich and oxygen-poor blood, allowing each circuit pulmonary and systemic to operate independently and at optimal pressures. This efficient system ensures maximum O2 delivery to meet high energy demands, which is why a powerful four-chambered heart evolved independently in their ancestors.