Which phylum includes insects, spiders, and crustaceans?

Which phylum includes insects, spiders, and crustaceans?

• A. Annelid
• B. Echinoderm
• C. Arthropod
• D. Mollusk

Answer: (C)

Jointed appendages, segmented bodies, and an exoskeleton made of chitin are hallmark features of arthropods. Insects, spiders, and crustaceans all share this body plan, which places them in the same phylum, Arthropoda (arthropods). These organisms grow by molting their exoskeletons and rely on a ventral nerve cord and an open circulatory system, all characteristic of arthropods. Annelids are segmented worms that lack jointed limbs and a chitinous exoskeleton, so they don’t fit this group. Echinoderms, such as sea stars, have radial symmetry as adults and a water vascular system with an internal skeleton rather than an external jointed shell. Mollusks, like snails and clams, typically have soft bodies with a muscular foot and, if present, a calcium carbonate shell, but no jointed exoskeleton. Therefore, the group that includes insects, spiders, and crustaceans is the arthropods.

Jointed appendages, segmented bodies, and an exoskeleton made of chitin are hallmark features of arthropods. Insects, spiders, and crustaceans all share this body plan, which places them in the same phylum, Arthropoda (arthropods). These organisms grow by molting their exoskeletons and rely on a ventral nerve cord and an open circulatory system, all characteristic of arthropods.

Annelids are segmented worms that lack jointed limbs and a chitinous exoskeleton, so they don’t fit this group. Echinoderms, such as sea stars, have radial symmetry as adults and a water vascular system with an internal skeleton rather than an external jointed shell. Mollusks, like snails and clams, typically have soft bodies with a muscular foot and, if present, a calcium carbonate shell, but no jointed exoskeleton. Therefore, the group that includes insects, spiders, and crustaceans is the arthropods.