Science (086) — AI-generated practice question

In fish, blood is pumped from the heart to the gills for oxygenation, then directly to the body. By the time it reaches body tissues, the blood pressure has dropped significantly, reducing the efficiency of oxygen delivery.

In double circulation (humans), the heart pumps blood twice — once through the lungs (pulmonary circuit) and once through the body (systemic circuit). This ensures that oxygenated blood is returned to the heart before being pumped to the body with full pressure. As a result, oxygenated and deoxygenated blood do not mix, and tissues receive a highly efficient, high-pressure supply of oxygen. This is essential for warm-blooded animals like mammals, which need more energy to maintain constant body temperature.

Source: Chapter 5, Section 5.4.1 — "Our pump — the heart"

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• The examiner expects two key points: (1) separation of oxygenated and deoxygenated blood prevents mixing, and (2) re-pressurisation of blood before systemic circulation ensures efficient oxygen delivery.
• Mention that this is especially important for birds and mammals (warm-blooded) with high energy demands — the textbook explicitly states this.
• Don't just define double circulation — compare it to fish and explain the advantage (the question word is "advantage").
• Avoid over-explaining anatomy; focus on the physiological benefit.