IB Biology HL A3.2.5 Hl Molecular Clock Questions

Sequence differences accumulate after clades diverge. Molecular clocks estimate divergence time from DNA or amino acid differences, but rates must be calibrated and can vary between genes or lineages.

Exam points

Explain that sequence differences accumulate after clades diverge.
Estimate divergence time from differences in DNA or amino acid sequences using a molecular clock.
Explain why molecular-clock rates must be calibrated and may vary between genes or lineages.

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