GENERAL HISTOLOGY

Detailed explanation-1: -The correct answer is (b). Echinoderms do not have gills.

Detailed explanation-2: -Structure and Function of Echinoderms. Echinoderms are named for their “spiny skin.” However, the spines aren’t on their skin. They are part of the endoskeleton. The endoskeleton consists of calcium carbonate plates and spines, covered by a thin layer of skin.

Detailed explanation-3: -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. Sea Stars: Most sea stars have five arms.

Detailed explanation-4: -Echinoderms are a phylum of marine invertebrates that include starfish, brittle stars, sea cucumbers, sea urchins, sand dollars, and crinoids. They are one of the most diverse groups of marine invertebrates and play important ecological roles from the near-shore environment to the deep seas.