1. Quick Refresher Anterior: head-end Posterior: tail-end
Dorsal: top-side
Ventral: bottom-side

2. Phylum Annelida many marine, freshwater, and terrestrial worms
Ex) earthworms
“segmented worms”
Divided by rings or segments
septa/septum (walls) separate segments
setae: small, bristle-like appendages

3. Earthworm

5. Giant Gippsland Earthworm of Australia

7. External Anatomy

8. Mouth cavity
brain
pharynx
Ventral nerve cord
esophagus
Seminal receptacle
Lateral heart
Ventral blood vessel
Seminal vesicles
nephridium
crop
Dorsal Blood vessel
gizzard

9. Internal Anatomy

10. Musculature Cuticle- thin external layer
Epidermis- outer cellular layer
Circular muscle layer
Longitudinal muscle layer

12. Obtain food by eating through and taking nutrients from soil
Digestive System
Obtain food by eating through and taking nutrients from soil

13. Digestive System Mouth- oral cavity (where soil enters)
Pharynx- where food is swallowed
Esophagus- Moves food down into the crop
Crop: temporary food storage compartment  before moving to gizzard
Gizzard:  food is ground using the rocks the earthworm also ingests
Intestine: digestion and absorption (into surrounding blood vessels)
Anus: Undigested material is removed from body

15. Respiratory System All annelids live in moist environments
most are aquatic. 
earthworms can survive only in damp soil. 
Gas exchange occurs at body surface through diffusion
NO LUNGS!

16. Circulatory System closed system
3 main vessels that supply the blood to organs within the earthworm → aortic arches, dorsal blood vessels, and ventral blood vessels
five pairs of lateral hearts (aortic arches) surround esophagus and pump blood
dorsal vessel- carry blood to front half
Ventral vessel- carry blood to back half

18. Nervous System Cerebral ganglia acts as “brain”
Prostomium: tongue-like lobe above mouth, allows earthworms to “feel” through soil

19. Reproductive System Earthworms are hermaphrodites
male and female reproductive organs present in each individual
Mates are introverted and attach with clitella to exchange sperm, then seperate
sperm stored in two sperm receptacles
cocoon forms (mucus from clitellum) -- earthworm will slide out of cocoon and the cocoon will pick up eggs and sperm from receptacles/pores
embryos develop in cocoon

23. What happens when an earthworm is cut in half?
Can it form two separate worms?
most organs are in anterior
can regenerate a new posterior
posterior end cannot regenerate a new anterior
so, no you don't get two new worms.