Earthworm Lab Report

March 23, 2013

General Biology II

Earthworm Lab

Earthworm

Abstract- In this lab we took an in dept look at the Annelid Earthworm. We dissected an earthworm and looked at the different internal structures that they possessed.

Materials- The materials used in this lab were a scalpel, forceps, gloves, dissecting pins compound microscope and a dissecting tray.

Methods- I began this experiment by applying my gloves and placing the earthworm on the dissecting tray with the light side of the worm down. Then I pined the two ends so that it wouldn't move. I drew a picture of the intact worm. I labeled the clitellum. Then I took the scalpel and made a shallow cut from the “head” of the worm to 2/3 down the body. I pined the worm as I made the cut, in order to get a better view of the organ system located above the clitellum. While cutting I noticed the epithelial, connective and muscular tissues that make up the covering of the worm. I drew all the structures of the worm such as the ganglia, dorsal blood vessel, hearts, crop, seminal versicle, pharynx, gizzard, and intestine. After drawing the different parts of the worm I removed the internal organs with the help of my forceps. I gently tugged and wiggled the organs carefully avoiding the dorsal nerve cord. The final thing I looked at was a cross section of an earthworm under the compound microscope. I drew the results I saw.

Results- The results of this lab were documented in my drawings. An intact worm has a prominent clitellum and is very segmented. I came across many “organs” that evolved into the ones found in larger animals today. The Earthworm had a “brain like” structure referred to as a ganglion which contained sensory nerves, located towards the mouth opening. The Ganglion is connected to the dorsal nerve cord which looks like a thin white line running straight down the organism. The pharynx is right below the ganglion, and it looks like a white blob. The worm also contains a series of hearts which...