Which of the following is a defining feature of arthropoda?

The defining feature of arthropoda is that they have a hard external skeleton, also known as an exoskeleton. This characteristic is crucial because it provides structural support, protection, and a barrier against desiccation for these organisms. The exoskeleton is made primarily of chitin, a substance that is remarkably strong yet lightweight, allowing for mobility and growth while offering necessary protection from environmental threats and predators.

In terms of classification, arthropods include a vast array of species, such as insects, arachnids, and crustaceans, all of which share this essential feature. The presence of an exoskeleton is integral to their physiology and plays a significant role in their adaptability to various environments, contributing to their success as a diverse and widespread group of organisms.

The other options do not accurately describe arthropods. Possessing a backbone pertains to vertebrates, rather than arthropods, which are invertebrates. Being exclusively aquatic is incorrect since many arthropods, such as insects, thrive in terrestrial habitats. Warm-blooded refers to endothermy, a characteristic of certain mammals and birds, which does not apply to arthropods, as they are ectothermic and rely on external environmental conditions to regulate their