EVERYDAY SCIENCE

Detailed explanation-1: -The body of all arthropods is covered by a chitinous exoskeleton. Chitin is a polymer of N-acetylglucosamine which provides protection as they are tough covering. Molluscs have a calcareous shell as exoskeleton and echinoderms have an endoskeleton made of calcareous spicules.

Detailed explanation-2: -It is made up of chitin. Thus, the exoskeleton of echinoderms is made up of a calcareous substance.

Detailed explanation-3: -Echinoderms do not have an exoskeleton. Explanation: Echinoderms belong to the phylum Echinodermata and are marine invertebrates. This phylum includes starfish, sea cucumbers, sea urchins, and sand dollars. Echinoderms do not have an exoskeleton.

Detailed explanation-4: -Echinoderm skeletons are made up of interlocking calcium carbonate plates and spines. This skeleton is enclosed by the epidermis and is thus an endoskeleton. In some, such as sea urchins, the plates fit together tightly.

Detailed explanation-5: -The exoskeleton of insects is composed of hard chitin, which is a polymer of acetylglucosamine and quite resistant to many chemicals.