[Campbell Biology P.771] Figure 34.6 illustrates that the same Hox genes BF1, Otx, and Hox3 ... | Practice Question

Figure 34.6 illustrates that the same Hox genes BF1, Otx, and Hox3 control the development of major regions of the vertebrate brain and are expressed in a corresponding pattern in the lancelet's nerve cord. What does this similarity suggest about the evolution of the vertebrate brain?

  • A: The vertebrate brain evolved independently of simpler chordate nervous systems.
  • B: The vertebrate brain is an elaboration of an ancestral structure similar to the lancelet's nerve cord tip.
  • C: Lancelets possess a fully-fledged brain homologous to the vertebrate brain.
  • D: Hox genes are unique to vertebrates and did not play a role in the nervous system development of early chordates.

Explanation

The text explicitly states, 'This suggests that the vertebrate brain is an elaboration of an ancestral structure similar to the lancelet's simple nerve cord tip.' The shared Hox gene expression patterns support this idea of a common evolutionary origin and subsequent elaboration.