Mollusks Soft-bodied invertebrates that normally have shells. Mollusks are classified according to their foot, whether or not they have a shell, and the type of shell they have. Mollusks are useful as a food source (clams, oysters, scallops). We also make jewelry (pearls) from mollusks. Have a body cavity for organs

Gastropods Single-shell (some don’t have a shell) Use a RADULA to eat with (tongue that works like a rough file). Includes slugs and snails This Photo by Unknown Author is licensed under CC BY-SA

Bivalves Two part shell Includes clams, scallops, and oysters.

Cephalopod No shell (usually). Includes squid, octopus, and nautilus They have the most specialized members

Segmented Worms (annelids) Use a GIZZARD to grind soil for food. Store food temporarily in a CROP Have a body cavity for organs. Bilateral symmetry Bristle-like setae help them move. Closed circulatory system. (has blood in blood vessels, unlike an open circulatory system. Larva look like spinning tops with cilia, much like mollusks, so they probably have a common ancestor

Arthropods Invertebrates with jointed appendages. Exoskeleton (hard outer covering) Exoskeleton gets outgrown so they shed it through molting. Keeps body from drying out. Usually lightweight. Supports and protects the body. Appendages: Antennae, legs, arms, claws, and pincers. Body cavity, nervous system, mouth and anus. Insects, arachnids, millipedes, centipedes, and crustaceans

Metamorphosis Change animals go through to become adults. Complete egg, larva (grub, caterpillar, maggot, etc.), pupa, adult Incomplete Egg, nymph (mini-adult), adult

Insects Largest group of complex invertebrates. Includes things like grasshoppers.

Spiders and ticks 8 legs 2 body segments Arachnids

Echinoderms Spiny skinned invertebrates Move with tube feet (like suction cups) Radial symmetry Internal skeleton Water – vascular system Opens shells with tube feet, inverts stomach onto the prey, enzymes dissolve the prey, sucks stomach and food back in.