Chapter 23: Invertebrate Diversity

Section Two: Animal Diversity Vertebrates and Invertebrates Vertebrates have a backbone, while invertebrates do not Animals can have radial or bilateral symmetry Radial symmetry: body parts are arranged in a circle Bilateral symmetry: body can be equally divided along one plane

Section Three: Sponges and Cnidarians No muscle or nerve cells Sessile: unable to move Considered most primitive animal on Earth Filter feeders: eat by straining particles from water Cnidarians Corals and jellyfish Have nematocyst for stinging

Section Four: Flatworms, Mollusks, and Annelids Flat with bilateral symmetry Tapeworm Mollusks Oysters, snails, squids, mussels, clams, scallops, octopus Have a radula: filelike feeding organ Annelids Segmented body Earthworm

Section Five & Six: Roundworms and Echinoderms Nematodes Many are parasites (pin worms or hookworms) Echinoderms Slow moving with radial symmetry Starfish, sea urchins, sand dollars, sea cucumbers