A4.1.9 (HL)—Adaptive radiation
Adaptive radiation diversifies one ancestral lineage into multiple related forms adapted to different niches, often leaving homologous structures as evidence.
- Syllabus
- First assessment 2025
- Objective
- A4.1.9
- Level
- HL
Exam analysis
Chance of appearing2%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper2
Typical marks3
Common command terms
- Outline
Scoring notes
- Common mistake
- Describing adaptive radiation as unrelated species becoming similar rather than related lineages diverging.
Recent exam appearances
May 2024Paper2 ["HL"] · TZ24(b)(i)[ 3 ]A4.1.9 (HL)—Adaptive radiation
November 2022Paper2 ["HL"] · TZ08(a)[ 3 ]A4.1.9 (HL)—Adaptive radiation
Practice this objective
Coverage 2022–2024 · Updated 15 Jul 2026
Concept essentials
- Adaptive radiation produces multiple related species from one ancestral species.
- Different niches impose different selection pressures on diverging groups.
- Homologous structures can reveal adaptive radiation from common ancestry.
- Niche specialization can reduce competition while promoting divergence.