Question

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

The outer skeleton provides protection, since invertebrates do not have backbones.
The outer skeleton surrounds the spinal cord, since invertebrates do not have backbones.
The outer skeleton helps invertebrates maintain homeostasis, since they lack spinal cords.
The outer skeleton helps invertebrates maintain homeostasis, since they lack membrane-bound organelles.

Answer 1

"The outer skeleton provides protection, since invertebrates do not have backbones."

Explanation: many invertebrates (insects, crustaceans, arachnids) have an exoskeleton that protects soft tissues and provides structural support and muscle attachment. Vertebrates instead have an internal (endo)skeleton — a backbone and bones — so they do not need an external shell.