1. PHYLUM ANNELIDA – segmented worms
Biology 112

2. Annelids
Representative species: common earthworm

3. Class Oligochaeta: Earthworms
``It may be doubted whether there are any other animals which have played so important a part in the history of the world as the earthworm.``
-Charles Darwin, 1881

4. Body complexity
Coelom – fluid filled body cavity surrounded by a mesoderm (room for organs)
Peritoneum - membrane in the coelom in which all organs are attached
2 sets of muscle tissue
1. body wall muscles to move the worm
2. digestive system muscles to move food

6. Class Oligochaeta: Earthworms
~ 2500 species
Many more cell layers than flat and round worms
Circulation: have blood to carry gases to and from body tissues
Blood in earthworms contains a red protein hemoglobin (just like in us!)
Have 5 hearts near the anterior end

8. Class Oligochaeta More complex digestive system than other worm phyla
They consume dirt (food and sand particles) via mouth, esophagus, pharynx, and then stores it in the crop.
After storage, food moves to the gizzard to be ground down, then to the intestine for digestion and absorption into the blood stream.
Undigested food moves out the anus

9. Earthworm digestion

10. Class Oligochaeta Setae are bristles that aid in movement
Each segment has 4 setae (except first and last ones)
Complex nervous system
Reproduce sexually
Hermaphrodites

12. Worm Charming??

13. Other members of Phylum Annelida
Class Hirudinea – leeches (blood sucking parasites)

14. Other members of Phylum Annelida
Class Polychaeta – marine worms