[Campbell Biology P.770] Based on the provided text, which statement best describes the evol... | Practice Question

Based on the provided text, which statement best describes the evolutionary relationship and key characteristics of cephalochordates like lancelets and urochordates like tunicates ?

  • A: Cephalochordates are more closely related to vertebrates than urochordates, and both retain all four chordate characters throughout their lives.
  • B: Urochordates are more closely related to other chordates, and their larval stage, but not adult, exhibits all four main chordate characters.
  • C: Both cephalochordates and urochordates are equally distant from vertebrates, and their main chordate characters are only visible during their larval stages.
  • D: Cephalochordates are primitive chordates that lack a notochord, while urochordates possess one only in their adult stage.

Explanation

The text states: 'Recent molecular studies indicate that the tunicates Urochordata are more closely related to other chordates than are lancelets. The chordate characters of tunicates are most apparent during their larval stage, which may be as brief as a few minutes' and 'In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious.' This directly supports option B.