What defines arthropods in the animal kingdom?

Arthropods are defined by their distinct body plan that features jointed appendages. This characteristic allows them a wide range of movement and adaptability, which is crucial for their survival in various environments. Additionally, arthropods are invertebrates, meaning they lack a backbone, distinguishing them from vertebrates like mammals or reptiles. The presence of an exoskeleton made of chitin further defines this group, providing support and protection.

The mention of jointed appendages is particularly significant as this trait is not shared by all invertebrates, making it a defining feature of arthropods. Examples of arthropods include insects, arachnids, crustaceans, and myriapods, all of which exhibit these jointed limbs. This allows them to interact with their environment in complex ways, such as walking, grasping, and swimming, depending on their ecological niche.