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IB Biology HL A3.2 Classification & Cladistics Question Bank

Practise using taxonomy, cladograms, molecular evidence and molecular clocks to infer evolutionary relationships and classification.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • explain why classification should reflect shared ancestry and can change when new evidence appears
  • interpret roots, nodes and branches to identify common ancestors and relative relatedness
  • use DNA or amino-acid differences and substitution data to construct or evaluate cladograms
  • compare Archaea, Eubacteria and Eukarya using rRNA, histones, cell walls and membrane lipids

Covered syllabus points

A3.2.1 (HL)—Need for classificationA3.2.2 (HL)—Difficulties with traditional hierarchyA3.2.3 (HL)—Advantages of evolutionary classificationA3.2.4 (HL)—CladesA3.2.5 (HL)—Molecular clockA3.2.6 (HL)—Constructing cladogramsA3.2.7 (HL)—Analysing cladogramsA3.2.8 (HL)—Testing classification correspondenceA3.2.9 (HL)—Three domains classification

A3.2 Classification and cladistics [HL only] question 1

[Maximum number: 4]

Outline the principles used by scientists to classify organisms.

A3.2 Classification and cladistics [HL only] question 2

[Maximum number: 1]

Which is the hierarchy of taxa in order of increasing numbers of species?

A

genus, family, order, class

B

class, order, genus, family

C

genus, family, class, order

D

class, order, family, genus

A3.2 Classification and cladistics [HL only] question 3

[Maximum number: 8]

Evolution is the change in the heritable characteristics of a population.

Explain how evolutionary relationships and cladograms can be used for classification.

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