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B3.2.14 (HL)—Single vs. double circulation

Double circulation separates pulmonary and systemic blood flow, allowing mammals to oxygenate blood at low lung pressure and deliver it systemically at high pressure.

Syllabus
First assessment 2025
Objective
B3.2.14
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1A
Typical marks1–8

Common command terms

  • Identify
  • Label
  • Explain

Scoring notes

Common mistake
Describing double circulation without explaining why blood must be pumped twice.

Recent exam appearances

November 2025Paper1A ["HL"] · TZ325[ 1 ]B3.2.14 (HL)—Single vs. double circulation
May 2025Paper1A ["HL"] · TZ326[ 1 ]B3.2.14 (HL)—Single vs. double circulation
November 2016Paper2 ["HL"] · TZ06(a)[ 8 ]B3.2.14 (HL)—Single vs. double circulation
Practice this objective

Coverage 2016–2025 · Updated 15 Jul 2026

Concept essentials

  • Fish have single circulation, while mammals have pulmonary and systemic circuits.
  • The right side of the mammalian heart pumps blood to the lungs.
  • The left side pumps oxygenated blood to body tissues at high pressure.
  • Double circulation separates oxygenated and deoxygenated blood.
ConceptIB Biology HL