Which group comprises invertebrates with jointed legs and an exoskeleton, including insects, arachnids, and crustaceans?

Which group comprises invertebrates with jointed legs and an exoskeleton, including insects, arachnids, and crustaceans?

• A. Arthropods
• B. Nematodes
• C. Flatworms
• D. Annelids

Answer: (A)

Jointed legs and an outer skeleton point to arthropods, a major invertebrate group. Arthropods have segmented bodies, paired jointed appendages, and a hard exoskeleton made of chitin that protects and supports them. Insects, arachnids, and crustaceans all fit here, showcasing their incredible diversity. The combination of jointed limbs and a protective exoskeleton, plus growth by molting, distinguishes them from other invertebrate groups that lack both features, such as nematodes (roundworms with no true skeleton), flatworms (flattened and without a skeleton), and annelids (segmented worms without an external skeleton).