Final answer:
Echinoderms, marine organisms in the phylum Echinodermata, are divided into five classes: Asteroidea (sea stars), Ophiuroidea (brittle stars), Echinoidea (sea urchins and sand dollars), Crinoidea (sea lilies or feather stars), and Holothuroidea (sea cucumbers), each with distinct body structures, modes of locomotion, and feeding mechanisms.
Step-by-step explanation:
Classes of Echinoderms
The phylum Echinodermata includes a variety of marine organisms that are categorized into five distinct classes, each with unique features and members:
These classes exhibit a pentamerous radial symmetry, a unique feature to echinoderms, and they typically undergo external fertilization. Echinoderms also have an endoskeleton made up of calcified plates, which can be highly variable between the different classes.