AP BIOLOGY

Detailed explanation-1: -Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum Echinodermata, characterized by a hard, spiny covering or skin.

Detailed explanation-2: -Echinoderms are “spiny-skinned” invertebrate animals that live only in marine environments.

Detailed explanation-3: -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. Adult echinoderms have radial symmetry.

Detailed explanation-4: -Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars (Fig. 3.83).

Detailed explanation-5: -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.