Which statement best explains why invertebrates often have outer skeletons but vertebrates do not?

• A. Vertebrates have a more advanced nervous system, eliminating the need for an exoskeleton.
• B. Invertebrates are generally larger than vertebrates, requiring an exoskeleton for structural support.
• C. Vertebrates have a higher metabolic rate, which makes an exoskeleton unnecessary.
• D. Invertebrates lack an internal skeleton, so they rely on an exoskeleton for support and protection.

Answer: (D)

Verified step by step guidance

1. Understand the basic difference between vertebrates and invertebrates: Vertebrates have an internal skeleton (endoskeleton), while invertebrates do not.
2. Recognize the function of an exoskeleton: It provides structural support and protection for invertebrates, which lack an internal skeleton.
3. Consider the evolutionary advantage: An exoskeleton allows invertebrates to protect their bodies from environmental hazards and predators.
4. Analyze the statement options: Eliminate options that incorrectly attribute the need for an exoskeleton to factors like nervous system complexity or metabolic rate.
5. Select the correct explanation: Invertebrates rely on an exoskeleton for support and protection due to the absence of an internal skeleton.