Chapter 2, Lesson 1 What are invertebrates?

1. Chapter 2, Lesson 1 What are invertebrates? Animals have many things in common. They also have many things that are different. These features can be used to classify animals.

2. Symmetry • Animals have different body shapes. Most animals have symmetry. Symmetry means that parts of an animal’s body match up. The body parts match up around a midpoint or line. Some animals have no symmetry. We can use symmetry to classify animals. • Sea urchins have symmetry. • Sponge does NOT have symmetry.

3. Backbone or No Backbone • Some animals have a backbone and others do not. A vertebrate is an animal that has a backbone. An animal without a backbone is an invertebrate. • Most animals are invertebrates. Some invertebrates have a hard outer covering. Others have a skeleton inside their bodies.

4. Invertebrate Groups • Mollusks • Cnidarians • Sponges • Echinoderms • Flatworms • Roundworms • Segmented worms • Arthropods

5. Sponge facts • Simplest kind of invertebrate • Most are shaped like a sack with an opening at the top • Live under water • Example: sponge

6. Cnidarians • Have arm-like parts called tentacles • Stinging cells at the end of each tentacle • Stun prey • Some stay in one place • Others float or swim • Examples: corals, jellyfish

7. Mollusks • Have a shell • Some have shells inside the body • Most live in water • Some swim • Others stay in one place • Snails and slugs are the only mollusks that live on land • Examples: clams, oysters, octopuses, squid, and snails

8. Echinoderms • Spiny skin • Have a support structure inside the body called an endoskeleton (means inside the body) • Example: sea urchin

9. Quick Check • What are two ways we can classify animals? • All mollusks live in water. _________ • A sponge is the simplest kind of invertebrate. __________ • An echinoderm has soft skin. _________ • Cnidarians have tentacles. ___________

10. What are arthropods? • The largest group of invertebrates is the arthropod group. • Arthropods have legs that bend. Their bodies have sections. • Some breathe with gills and others through tubes. • Every arthropod has an exoskeleton. This is a hard covering on the outside of the body.

11. Exoskeleton • Keeps the animal safe • Keeps the animal from drying out. • Quick Check • An arthropod has a(n) ________ covering. • The covering is on the ________ of the body. • Examples: lady beetle, praying mantis, moth

12. More examples of arthropods • Insects- have one pair of antennae, three pairs of legs, one or two pairs of wings, and three body sections. • Arachnids- include spiders, ticks, and scorpions. They have four pairs of legs, two body sections, and fangs.

13. Examples Continued • Crustaceans- such as crabs and shrimps, have two pairs of antennae and two to three body sections. They can chew • Centipedes and millipedes- Centipedes have one pair of legs on each body section. Millipedes have two pairs of legs on each body section.

14. How are worms classified? • There are 3 kinds of worms: flatworms, roundworms, and segmented worms.

15. Flatworms • Simplest worms • Flat bodies • They have a head and a tail • Most do not hurt other living things • Some live inside other animals.

16. Roundworms • They have thin bodies with pointed ends. • Not as thin as flatworms • Food comes into opening • Waste leaves through another opening. • Most live inside other animals.

17. Segmented Worms • Bodies are divided into parts, or segments. • The parts are the same, except for the head and tail ends. • Each has an opening for the digestive system. • Most live on land • They do NOT live inside other animals. • Earthworms, sandworms, and leeches are segmented worms.

18. Quick Check • Write the letter for the fact about each worm. • ______flatworms • ______ segmented worms • ______ roundworms • A. thin bodies with pointed ends • B. do not live in other animals • C. simplest kind of worms