AP BIOLOGY

Detailed explanation-1: -Echinoderms are radically symmetrical, and the body is usually divided into five parts or multiples of five. This five-sided radial structure of echinoderms makes the body strong (Fig.

Detailed explanation-2: -One characteristic of an echinoderm is that they all have pentamerous radial symmetry. This simply means they all have 5 equal body parts. You can divide these animals into five equal parts, and every part is the same. For example, most sea stars have five arms or a multiple of five arms.

Detailed explanation-3: -Echinoderms have a spiny endoskeleton. They have radial symmetry as adults but bilateral symmetry as larvae. Echinoderms have a unique water vascular system with tube feet.

Detailed explanation-4: -Echinodermata means “spiny-skinned, ” and this phylum includes such spiny animals as sea stars and sea urchins. The skin covers an internal skeleton. Like cnidarians (e.g., jellyfish and corals), the bodies of echinoderms are organized around a central point; they exhibit radial symmetry.

Detailed explanation-5: -Echinodermata: Systematics. In traditional taxonomy, there are five classes of living echinoderms: Crinoidea (sea lilies), Asteroidea (starfish), Ophiuroidea (brittle stars or snake stars), Echinoidea (sea urchins and sand dollars), and Holothuroidea (sea cucumbers).