Which of the following is NOT one of the five key characteristics of chordates?

• A. Exoskeleton
• B. Pharyngeal slits
• C. Dorsal hollow nerve cord
• D. Notochord

Answer: (A)

Verified step by step guidance

1. Understand the key characteristics of chordates. Chordates are a group of animals that have certain features at some point in their life cycle.
2. Identify the five key characteristics of chordates: 1) Notochord, 2) Dorsal hollow nerve cord, 3) Pharyngeal slits, 4) Post-anal tail, and 5) Endostyle or thyroid gland.
3. Review the options given in the problem: Exoskeleton, Pharyngeal slits, Dorsal hollow nerve cord, and Notochord.
4. Compare each option with the five key characteristics of chordates. Note that 'Exoskeleton' is not listed as one of the key characteristics.
5. Conclude that 'Exoskeleton' is the correct answer as it is not one of the five key characteristics of chordates.