Science (086) — AI-generated practice question

Labelled Diagram of the Human Heart:
(Draw a diagram showing: Right Atrium, Right Ventricle, Left Atrium, Left Ventricle, Pulmonary Artery, Pulmonary Vein, Aorta, Vena Cava, and Valves)

Mechanism of Double Circulation:

Deoxygenated blood from the body enters the right atrium → passes to the right ventricle → pumped to the lungs via pulmonary artery (pulmonary circulation). In the lungs, CO₂ is removed and blood is oxygenated. Oxygenated blood returns to the left atrium via pulmonary vein → passes to the left ventricle → pumped to the entire body via aorta (systemic circulation). Since blood passes through the heart twice in one complete cycle, it is called double circulation.

Why necessary for mammals and birds but not fish:

Mammals and birds are warm-blooded; they constantly use energy to maintain body temperature, requiring a highly efficient oxygen supply. Complete separation of oxygenated and deoxygenated blood prevents mixing, ensuring this efficiency. Fish have only two-chambered hearts; blood passes through the heart only once per cycle (single circulation), which is sufficient as they do not regulate body temperature internally.

Source: Chapter 5, Section 5.4.1 — Transportation in Human Beings

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• Diagram is compulsory — examiners deduct marks if it is absent or unlabelled. Label at least: four chambers, pulmonary artery/vein, aorta, vena cava.
• The two loops to name: pulmonary circulation (heart → lungs → heart) and systemic circulation (heart → body → heart).
• The key reason for double circulation in mammals/birds: warm-blooded = high energy need = efficient O₂ supply required. Fish are cold-blooded and single circulation suffices.
• Avoid mixing up pulmonary artery (deoxygenated) and pulmonary vein (oxygenated) — a common error examiners watch for.