Earthworm Virtual Dissection

Gianna Haskin

Objectives

The earthworm, Lumbricus terrestris, is a member of the phylum Annelida. The purpose of an earthworm dissection, is to to observe the structures of male and female Lumbricus terrestris. In this lab, you will see first hand the internal and extrenal structure of an earthworm and be able to determine its organs and their functions.

Background

Earthworms are invertebrates part of phylum Annelida. They are highly developed worms made up of ring-like segments called annuli, with bilateral symmetry and external bristles called setate. Earthworms live under the Earth, in the soil, and prefere to moist warm climates. Every garden needs earthworms. They aerate the soil, fertilize it with their waste and feed on leaves, dirt and other organic matter. They are a source of food for birds, snakes and beetles. The earthworm provides a necessary service in sustaining agriculture. Each segment on an earthworm’s body has a number of bristly hairs, called setae. These hairs provide some grip to help the earthworm move through the soil.

External Anatomy

Internal Anatomy

Step 1

Pin the earthworm on the mouth, anus, clitellum.

Step Two

Make a shallow cut from the mouth to the clitellum, making sure to avoid puncturing the earthworm.

Step Three

Pin the skin of the earthworm so that you may view its internal organs. Identify the organs and record what you see.

Digestive System

The digestive system consists of the pharynx, the esophagus, the crop, the intestine and the gizzard. Food such as soil enters the earthworm’s mouth where it is swallowed by the pharynx. Then the soil passes through the esophagus, which has calciferous glands that release calcium carbonate to rid the earthworm’s body of excess calcium. After it passes through the esophagus, the food moves into the crop where it is stored and then eventually moves into the gizzard. The gizzard uses stones that the earthworm eats to grind the food completely. The food moves into the intestines as gland cells in the intestine release fluids to aid in the digestive process. The intestinal wall contains blood vessels where the digested food is absorbed and transported to the rest of the body.

Extra Information

Earthworms are indigenous to Europe, but are now abundant in North America and western Asia. Earthworms are are usually 7-8 inches long, but have been known to get up to an outstanding length of 14 inches! An earthworm's lifespan is up to 6 years, and They are the main contributors to enriching and improving soil for plants, animals and even humans. Here is a fun website about earthworms: http://www.biokids.umich.edu/critters/Oligochaeta/

WORKS CITED

"Common Earthworm." National Geographic. N.p., n.d. Web. 08 Apr. 2014.

"Earthworms." Earthworms. N.p., n.d. Web. 03 Apr. 2014.