1. Worms

2. Flatworms Flatworms are invertebrate. It has a head, or anterior end, and tail, or posterior end. Like most animals, flatworms are bilaterally symmetrical. Examples: Tape worms & blood flukes.

3. Bilateral Symmetry  Body plan in which an animal can be divided into two equal sides.

4. Structure  Gastrovascular cavity – gut with a single opening.  Cephalization – concentration of sensory organs towards the anterior end.

5. Digestion & Excretion  Pharynx – takes up food.  Enzymes excreted to break down material.  Nutrients diffuse to other parts of the body.

6.  Flame cells – collect excess water.  Water travels through network of tubules and is eliminated through pores on the body surface.

7. Roundworms (Nematodes)  Examples: hookworms, pinworms  Pseudocoelomates: hollow fluid filled cavity - lined by mesoderm on the outside and endoderm on the side.

8. The body of a roundworm It has a complete digestive tract:  Two openings: mouth and an anus at opposite ends.  Food only travels one way.

9. Segmented Worms: Annelids  Their bodies are divided in segments, or sections.  Example: Earth Worm, leeches

10. Characteristics  Symmetry – Bilateral  A segmented coelom – allows different parts of the body to move independently.  Setae – external bristles.

11. Coelom  The body cavity of annelids is called coelom.  A coelom is a fluid-filled cavity completely lined by tissue that originated from mesoderm tissue.

12. Structure and Movement  Anchor middle section using setae.  Contraction of the longitudinal muscles causes the worm to move forward.

13. Feeding and Digestion  Pharanx – muscular structure that sucks in soil.  Esophogus – food passes through here.  Crop – temporary storage  Gizzard – grinds soil, breaking up organic matter.  Intestine – absorbs organic compounds and nutrients.  Anus – expels waste.

14. Circulation  O 2, CO 2, nutrients & wastes transported through blood vessels.  Aortic arches connect the dorsal and ventral blood vessels.  Contraction of vessels and arches circulates the blood.

15. Respiration  Obtaining Oxygen: –Diffusion through skin  Nephridia: –Tubes that eliminate excess water and wastes.

16. Reproduction  Hermaphrodites  Setae and mucus secreted by the clitellum hold the worms together.  Secrete sperm into the mucus and it is stored in the seminal receptacle.

17. Reproduction  After they separate the clitellum secretes a tube made of mucus and chitin.  This tube picks up the worm’s eggs and sperm  fertilization.