[Campbell Biology P.523] According to Figure 22.7 and its accompanying text, what do the unl... | Practice Question

According to Figure 22.7 and its accompanying text, what do the unlabeled branches in Darwin's 1837 sketch primarily represent?

  • A: Groups of living organisms in the present day.
  • B: Extinct groups of organisms.
  • C: Common ancestors from which new lineages branched.
  • D: Unidentified or unknown species.

Explanation

Figure 22.7's description explicitly states: 'Branches that end in twigs labeled A-D represent particular groups of living organisms; all other branches represent extinct groups.' Thus, the unlabeled branches are those that terminated, indicating extinction.