Phylogeny

AP Biology· difficulty 2/5

A B C Branch lengths proportional to substitutions

On a phylogram with branch lengths proportional to molecular changes, which of the following is true?

  • A

    Long branches imply common ancestry; short branches do not

  • B

    Longer branches indicate more substitutions accumulated along that lineage

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  • C

    Branch length is irrelevant to evolutionary inference

  • D

    Branch length always equals time elapsed

Explanation

In a phylogram, branch length scales with evolutionary change (e.g., substitutions per site). Different lineages may evolve at different rates, so branch length and time are not equivalent.

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