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Multiple Choice
Which of the following characteristics is found in vertebrates, but not in tunicates or lancelets?
A
A dorsal hollow nerve cord
B
Pharyngeal slits
C
A vertebral column (backbone)
D
A notochord
Verified step by step guidance
1
Understand the question: The problem asks us to identify a characteristic that is unique to vertebrates and not found in tunicates or lancelets. The options provided include anatomical features common in chordates, so we need to carefully analyze each one.
Review the characteristics of chordates: All chordates, including tunicates, lancelets, and vertebrates, share four key features at some stage in their life cycle: a dorsal hollow nerve cord, pharyngeal slits, a notochord, and a post-anal tail.
Analyze the options: (1) A dorsal hollow nerve cord is present in all chordates, including tunicates and lancelets. (2) Pharyngeal slits are also a shared feature of all chordates. (3) A notochord is present in all chordates, although in vertebrates it is replaced by the vertebral column during development. (4) A vertebral column (backbone) is unique to vertebrates and distinguishes them from tunicates and lancelets.
Conclude the reasoning: The vertebral column is the defining feature of vertebrates. It replaces the notochord during development and provides structural support and protection for the spinal cord, which is not present in tunicates or lancelets.
Final step: Based on the analysis, the correct answer is 'A vertebral column (backbone)' because it is unique to vertebrates and not found in tunicates or lancelets.