Coelenterates are also very primitive. Their mouths, which take in food and get rid of waste, are surrounded by stinging tentacles. Some coelenterates are jellyfish, corals, and sea anemones. Echinoderms include starfish, sea urchins, and sea cucumbers. They live in seawater and have external skeletons.
Mollusks are soft-bodied animals, which often live in hard shells.
They include snails, slugs, octopus, squid, mussels, oysters, clams, scallops, chitons, and cuttlefish. Mollusks are the second-largest group of invertebrates, with 50,000 living species. Arthropods are the largest and most diverse of all animal groups. This Page Printer-Friendly Version BoxerMath Classroom Connect EdGate PH School Scott Foresman SkyLight Professional Development Find a wealth of learning resources for your classroom. Professional and Classroom Learning resources.