GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms are “spiny-skinned” invertebrate animals that live only in marine environments. Two major divisions are recognized by biologists: principally attached, usually stalked forms of the Pelmatozoa; and unattached free-moving forms of the Eleutherozoa.

Detailed explanation-2: -Spiny skinned animals are placed in Echinodermata. The spines on the skin in echinoderms are part of the endoskeleton. The endoskeleton is made up of calcium carbonate plates called ossicles that bear spines which project outside.

Detailed explanation-3: -Sea stars and their cousins belong to a group called Echinoderms. Echinoderm means spiny skin. If we break the word down echino = spiny and derm= skin, so these animals are spiny-skinned. Sea stars and their cousins are part of a group of spiny-skinned animals.

Detailed explanation-4: -In addition to radial symmetry, echinoderms have a water-vascular system. True. True or False? The hard, spiny skin of an echinoderm is called an exoskeleton.