GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms are deuterostome invertebrate animals, phylogenetically most closely related to hemichordates and to chordates. They are exclusively marine-living, with a wide range of habitats from the deep sea to the intertidal region.

Detailed explanation-2: -Echinoderms lack respiratory and excretory systems. Instead, the thin walls of their tube feet allow oxygen to diffuse in and wastes to diffuse out. Echinoderms also lack a centralized nervous system. They have an open circulatory system and lack a heart.

Detailed explanation-3: -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-4: -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.