Final answer:
Cephalopods perform locomotion through jet propulsion by forcefully ejecting water from their mantle cavity. This movement allows them to swim swiftly through their marine habitats.
Step-by-step explanation:
Cephalopods, such as octopuses, squids, cuttlefish, and nautilus, are known for their unique mode of locomotion within the Phylum Mollusca. These animals primarily move through the water via a method known as jet propulsion. By contracting their mantle cavity, cephalopods are able to forcefully eject streams of water, propelling themselves swiftly through their marine environments. While nautilus species regulate their buoyancy with gas or water in a multi-chambered shell, other cephalopods, like the octopus, lack an external shell entirely. With advanced nervous systems and complex eyes, cephalopods exhibit remarkable behavior, such as rapid color change for camouflage or predation. Moreover, they are dioecious, with separate sexes, and the development from eggs to juveniles occurs without a larval stage, distinguishing them from many other aquatic mollusks.