Final answer:
The claim that arthropods lack external sensory structures due to their exoskeleton is false; arthropods possess various such structures, including antennae and sensory hairs.
Step-by-step explanation:
The statement that arthropods do not have external sensory structures because the hard exoskeleton prevents it is false. Arthropods, such as insects, spiders, and crustaceans, indeed have a hard exoskeleton, but this exoskeleton does not inhibit the presence of sensory structures. The arthropod exoskeleton, which is primarily composed of chitin and sometimes reinforced by calcium carbonate, offers numerous advantages including protection against predators, prevention of water loss—particularly for terrestrial species—, and providing a framework for muscle attachment. However, arthropods are also equipped with a variety of external sensory structures such as antennae, compound eyes, and sensory hairs, which are sophisticated and allow them to interact with their environment effectively.