Which term best describes animals with jointed limbs, segmented bodies, and an exoskeleton that molts?

• A. Invertebrates
• B. Nematodes
• C. Mollusks
• D. Arthropods

Answer: (D)

Arthropods are defined by three main features: bodies that are segmented, jointed appendages, and an exoskeleton made of chitin that must be shed as the animal grows. This combination explains why they’re the best term for animals with jointed limbs, segmented bodies, and an exoskeleton that molts. The molting process (ecdysis) allows these creatures to increase in size while keeping the protective exoskeleton, even though they must periodically shed it and form a larger one.

Other groups don’t fit all these criteria. A broad label like invertebrates is too general and doesn’t specify the jointed limbs or molting exoskeleton. Nematodes lack segmented bodies and jointed limbs, though they do shed a cuticle, that’s not the same jointed, segmented body plan with a moltable exoskeleton. Mollusks may have a shell but do not exhibit jointed limbs or a molts-type external skeleton in the way arthropods do.