[Campbell Biology P.612] In the "Applying Parsimony to a Problem in Molecular Systematics" t... | Practice Question

In the "Applying Parsimony to a Problem in Molecular Systematics" technique described in Figure 26.15, what do the "purple hatch marks" found on the branches of the phylogenetic trees specifically represent?

  • A: The length of the evolutionary branch.
  • B: A single base-change event.
  • C: A common ancestor shared by the species.
  • D: A point of speciation.

Explanation

Step 3 of the 'Technique' section explicitly states: 'In the tree on the left, a single base-change event, represented by the purple hatch mark on the branch leading to species I and II and labeled 1/C, indicating a change at site 1 to nucleotide C , is sufficient to account for the site 1 data.' This confirms that the purple hatch marks signify base-change events.