Earthworm Dissection

•Phylum Annelida—segmented worms

•Over 1000 species! (earthworms, marine worms, leeches)•Segments allow for specialization of tissue and efficiency of movement

• “Tube within a tube” digestive system

• Breath through skin by diffusion

• Closed circulatory system

• 2 kinds of muscle for movement: – Circular (shrink and spread)– Longitudinal (shorten and lengthen)

Step 1-Locate the dorsal, ventral, anterior, and posterior sides

Step 2-Find the sperm ducts and clitellum

Step 3-Find the mouth and anus

Step 4-Place 2 pins in the worm

Step 5-Carefully cut the worm

Why do you think there is a thin, layer here?

•Cut all the way to the clitellum

Step 6-Pin the worm, exposing all internal organs

Step 7-Identify all internal organs

Pharynx—used to suck in food

Esophagus—food travels through this after pharynx

Seminal vesicles—produce sperm***Remove with tweezers

*Crop-stores food*Gizzard-grinds up food (very strong)

crop gizzard

Intestines!!!!!-digestion and absorption of food

What are these small organs???

aortic arches/hearts

This thin dark-red tube extends the entire length of the worm. It is the dorsal blood vessel !!!