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A3.2.6 (HL)—Constructing cladograms

Cladograms are constructed by comparing traits or aligned sequences, then choosing trees that best explain shared similarities and differences parsimoniously.

Syllabus
First assessment 2025
Objective
A3.2.6
Level
HL

Exam analysis

Chance of appearing7%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper2
Typical marks1–3

Common command terms

  • Explain
  • State
  • Describe
  • Discuss
  • Outline

Scoring notes

Common mistake
Choosing a cladogram from visual layout rather than shared trait or sequence evidence.

Recent exam appearances

May 2025Paper2 ["HL"] · TZ37(d)[ 1 ]A3.2.6 (HL)—Constructing cladograms
May 2025Paper2 ["HL"] · TZ37(b)[ 3 ]A3.2.6 (HL)—Constructing cladograms
May 2023Paper2 ["HL"] · TZ28(c)[ 7 ]A3.2.6 (HL)—Constructing cladograms
May 2022Paper1 ["HL"] · TZ119[ 1 ]A3.2.6 (HL)—Constructing cladograms
May 2019Paper2 ["HL"] · TZ24(b)[ 3 ]A3.2.6 (HL)—Constructing cladograms
Practice this objective

Coverage 2015–2025 · Updated 15 Jul 2026

Concept essentials

  • Cladograms can be built from traits, DNA sequences, RNA sequences, or protein sequences.
  • Sequence alignment allows comparable bases or amino acids to be compared.
  • More similar sequences usually indicate closer evolutionary relationship.
  • Parsimony favours the tree requiring the fewest evolutionary changes.
  • Molecular cladistics can reclassify groups that morphology placed incorrectly.
ConceptIB Biology HL