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A2.3.6 (HL)—Rapid evolution in viruses

Large populations, short replication cycles, error-prone RNA copying, recombination, and strong selection allow many viruses to evolve rapidly and evade existing host defenses.

Syllabus
First assessment 2025
Objective
A2.3.6
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–2

Common command terms

  • Suggest
  • Outline

Scoring notes

Common mistake
Attributing rapid viral evolution only to mutation while omitting replication rate, recombination, or selection.

Recent exam appearances

November 2025Paper2 ["HL"] · TZ32(b)[ 2 ]A2.3.6 (HL)—Rapid evolution in viruses
May 2017Paper1 ["HL"] · TZ137[ 1 ]A2.3.6 (HL)—Rapid evolution in viruses
Practice this objective

Coverage 2017–2025 · Updated 15 Jul 2026

Concept essentials

  • Error-prone replication creates mutations especially rapidly in many RNA viruses.
  • Short generation times and large populations expose selection to abundant variation.
  • Recombination or genetic exchange can generate new viral combinations.
  • Natural selection increases variants with reproductive or immune-escape advantages.
  • Rapid antigen change can weaken secondary immune responses and complicate control.
ConceptIB Biology HL