What phylum is characterized by having a jointed exoskeleton?

The phylum characterized by having a jointed exoskeleton is Arthropoda. This group includes insects, arachnids (like spiders and scorpions), crustaceans (such as crabs and lobsters), and myriapods (like centipedes and millipedes). The jointed exoskeleton, made of chitin, provides protection and structural support while allowing for flexibility and movement, which is essential for the diverse range of habitats and lifestyles that arthropods occupy.

In contrast, Annelida, which includes segmented worms, use a coelomic body plan without an exoskeleton, and their bodies are rather soft. Nematoda, or roundworms, possess a tough, flexible cuticle but lack the segmented, jointed structure that characterizes arthropods. Molluska, which includes snails and clams, have a hard shell, but their body structure does not include the jointed features seen in arthropods. This unique characteristic of Arthropoda not only aids in movement but also allows for specialization in various ecological niches, highlighting their evolutionary success.