Final answer:
Sea stars do not have a jaw-like structure; they belong to the echinoderms and have a unique anatomy with a hydrostatic skeleton and tube feet used for various functions including feeding.
Step-by-step explanation:
Sea stars, also known as starfish, do not have a jaw-like structure. Instead, sea stars are part of a group called echinoderms, which includes sea urchins, sand dollars, brittles stars, sea cucumbers, sea lilies, and feather stars. These marine animals have unique body plans and feeding mechanisms that do not involve jaws. In sea stars, their anatomy is characterized by a pentaradial pattern and a water vascular system that is crucial for their locomotion and feeding. The sea star's skeleton is called a hydrostatic skeleton, which uses the pressure of the body's fluid to maintain its shape and help with movement.
Specifically, sea stars have tube feet that aid in locomotion, attaching to substrata, and capturing food. During feeding, some species of sea stars can evert their stomachs to engulf and digest food externally. This feeding process is quite different from the mechanism seen in gnathostomes, which are jawed vertebrates. While gnathostomes have evolved jaws that allow for grasping and tearing food, sea stars use their tube feet and other adaptations for feeding.