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IB Biology HL A3.2.7 Hl Analysing Cladograms Questions

In a cladogram, nodes represent common ancestors or speciation events, and branch points show the order of divergence. Interpret roots, terminal branches, ingroups, outgroups and sister groups rather than judging relationships by end-position similarity.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Interpret nodes as common ancestors or speciation events.
  • Use branch points to determine the order of divergence rather than judging relationships by the end positions of branches.
  • Use roots, terminal branches, ingroups, outgroups and sister groups to interpret a cladogram.

IB Biology HL A3.2.7 Hl Analysing Cladograms Questions question 1

[Maximum number: 2]

The gut of a healthy human contains more than 1000 species of bacteria. Some of these species are shown in the cladogram.

Cladogram with species X branching beside a group containing M. luminyensis and paired M. smithii/M. stadmanae. A separate main branch contains E. faecalis and paired B. fragilis/B. stercosis.

Identify, with a reason, whether the cladogram shows species X is more closely related to M. luminyensis or to E. faecalis.

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