1. Chapter 23: Invertebrate Diversity

2. 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

3. 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

4. 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

5. 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