2. Spineless Animals Invertebrates

3. Sponges Sponge is the simplest kind of an invertebrate. Shaped like a sack with an opening at the top It’s body is made of 2 cell layers Body is hollow inside Live in water Adults stay in one place, their kids float around

4. Mollusks Mollusks are an invertebrate that has a soft body and a shell Most live in water, snails and slugs live on land Some stay in one place, others float. Shells are sometimes inside their bodies.

5. Cnidarian A cnidarians (nye-DAYR-ee-uhn) is an animal with arm like parts called tentacles. Sting their prey with stinging tentacles Some stay in one place, others float around

6. arthropods Arthropods have jointed legs and a body that is divided into sections. Largest group of invertebrate Have exoskeleton, hard cover protects the body 4 major groups: insects, arachnids, crustaceans, centipedes/millipedes

7. insects 1 pair of antennae 3 pairs of legs 1-2 pairs of wings 3 body sections

8. arachnids 4-5 pairs of legs 2 body sections fangs

9. centipedes/millipedes Centipedes have 1 pair of legs on each body section Millipedes have 2 pair of legs on each body section

10. crustaceans 2 pair of antennae 2-3 body sections They can chew

11. flatworm Flat bodies, head and a tail Most are harmless Some live inside the bodies of other animals

12. roundworms Thin bodies with pointed ends One way digestion system Most roundworms live inside the bodies of other animals

13. Segmented worms Bodies have 3 layers and divided into segments Have a head and tail- both have an opening to the digestion system Only live on land- none live inside an animal’s body