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IB Biology HL A3.2.5 Hl Molecular Clock Questions

Relate accumulated DNA or amino-acid substitutions to divergence time and use molecular differences to compare molecular-clock estimates.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Relate the number of DNA or amino-acid substitutions to the time since lineages diverged.
  • Use molecular differences in sequence or cytochrome data to estimate or compare divergence times with a molecular clock.

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Study A3.2.5 (HL)—Molecular clock conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Biology HL A3.2.5 Hl Molecular Clock Questions question 1

[Maximum number: 1]

The evolutionary clock estimates the time elapsed since species separated from a common ancestor based on fossil evidence. The graph shows the number of differences in the DNA sequences (nucleotide substitutions) coding for certain polypeptides in 11 closely related mammals.

Figure for Question IB Biology HL A3.2.5 Hl Molecular Clock Questions question 1 — IB Biology HL

State the relationship between divergence time and number of substitutions.

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