GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms are the group of animals that consists of sea stars, sea urchins, sea cucumbers, brittle stars and crinoids. They are part of the larger group of animals called INVERTEBRATES. We have a backbone and fish have a backbone, but sea stars and their cousins DO NOT have bones.

Detailed explanation-2: -Echinoderms are deuterostome invertebrate animals, phylogenetically most closely related to hemichordates and to chordates.

Detailed explanation-3: -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.