GENERAL HISTOLOGY

Detailed explanation-1: -The phylum echinoderms is divided into five extant classes: Asteroidea (sea stars), Ophiuroidea (brittle stars), Echinoidea (sea urchins and sand dollars), Crinoidea (sea lilies or feather stars), and Holothuroidea (sea cucumbers).

Detailed explanation-2: -Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars (Fig. 3.83). Although they may appear very different, echinoderms all have two major defining characteristics that set them apart from all other animals: a water vascular system and five-sided radial symmetry.

Detailed explanation-3: -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-4: -They have a star-like appearance and are spherical or elongated. They are exclusively marine animals. The organisms are spiny-skinned. They exhibit organ system level of organization. They are triploblastic and have a coelomic cavity. The skeleton is made up of calcium carbonate. More items