Which phylum includes animals with segmented bodies, jointed appendages, and an exoskeleton?

Which phylum includes animals with segmented bodies, jointed appendages, and an exoskeleton?

• A. Echinoderms
• B. Arthropods
• C. Annelids
• D. Mollusks

Answer: (B)

Arthropods are defined by three key features that commonly occur together: a segmented body, jointed appendages, and an external exoskeleton. The segmentation provides a flexible framework for specialization, allowing body regions to take on different functions. Jointed appendages give a wide range of movements and abilities, from walking and swimming to manipulating objects and sensing the environment. The exoskeleton, usually made of chitin, protects the organism and supports the body, though it requires molting as the animal grows. Because these three traits appear together, this phylum is the best match for the description. Examples include insects, spiders, crustaceans, and millipedes, which show how segmentation, joints, and an outer skeleton combine to create a highly diverse group. The other groups lack one or more of these features: they may have an internal skeleton or lack jointed limbs, or they do not have a true external exoskeleton with jointed, segmented bodies.