Science — AI-generated practice question

Double Circulation in Human Beings:

In human beings, blood passes through the heart twice in one complete cycle — this is called double circulation.

1. Pulmonary circulation: De-oxygenated blood from the body enters the right atrium → right ventricle → pumped to the lungs for oxygenation.
2. Systemic circulation: Oxygenated blood from the lungs returns to the left atrium → left ventricle → pumped to the rest of the body.

The right side of the heart handles de-oxygenated blood; the left side handles oxygenated blood. The separation of the two sides prevents mixing of oxygenated and de-oxygenated blood.

Why it is necessary:

Double circulation ensures a highly efficient supply of oxygen to body tissues. Mammals and birds are warm-blooded — they constantly use energy to maintain body temperature. Keeping oxygenated and de-oxygenated blood completely separate allows oxygen-rich blood to reach tissues at high pressure, meeting their high energy demands.

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

---

• Examiners expect two named circuits (pulmonary + systemic) with direction of blood flow.
• Mention the four chambers and their roles briefly.
• The "why necessary" part must link warm-blooded nature → high energy needs → efficient O₂ supply. This is directly from the textbook and is a common scoring point.
• Contrast with fish (single circulation) or amphibians (3-chambered, mixing allowed) can earn extra credit if word count allows.