AP BIOLOGY

Detailed explanation-1: -Echinoderm skeletons are made up of interlocking calcium carbonate plates and spines. This skeleton is enclosed by the epidermis and is thus an endoskeleton.

Detailed explanation-2: -Echinoderms possess a unique internal skeleton (or endoskeleton) composed of thousands to millions of calcium carbonate components known as ossicles. Similar to a complicated 3-D puzzle, these pieces are infused with tissue and covered by an epidermis, or skin like covering.

Detailed explanation-3: -The Phylum Echinodermata doesn’t always have spiny skin, or a spiny surface, but these animals do all share a calcium carbonate internal skeleton, or endoskeleton.

Detailed explanation-4: -The bodies of echinoderms are made of hard calcium-based plates that are often spiny and always covered by a thin skin. The echinoderm skeleton is thus on the inside-called an endoskeleton.

Detailed explanation-5: -Echinoderms have an internal skeleton made of bony plates (ossicles) of calcium carbonate. They deposit this material after extracting dissolved calcium and carbonate (bicarbonate) ions from sea water. In some species, such as the sea urchin, plates of the skeleton are locked together to form a rigid structure.