The Earthworm

Earthworm Virtual Dissection Lab : Hillary Huang

Lumbricus terrestris

Earthworms are in an order of Haplotaxida. They belong in the kingdom Animalia under the phylum Annelida. The earthworm's body is segmented and may look like many little rings fused together. The earthworm may have up to 100-150 segments and each segment includes muscles and bristles known as the setae. Segmentation of the earthworm's body provides movement and allows the earthworm to become flexible and strong. They are well adapted to living in soil and the mucus coating helps oxygen pass through the earthworm when it is out of the soil, or underwater.

Background information

Earthworms are mostly in soil but there may be times when earthworms are in a different habitat such as an underwater location. Earthworms decompose dead organisms in the soil and keep it healthy. They are the main contributors to nourishment and enrichment in soil. When earthworms move through the soil, they make tiny tunnels that allows water to properly enter the ground and into the roots of plants. They also eat organic matter such as decaying leaves ( which is pretty useless to the plants) and they release their wastes known as castings which provide nutrients in the soil.

Earthworms do not prey on anything since they eat decaying leaves but they do have predators such as moles, birds, and raccoon. There are many other predators since Earthworms contain a lot of nutrients but those are just a few examples. However, earthworms have ways to hide from their predators. They adapted to have brown skin to camouflage with the soil and they also have segmented bodies to become flexible.

Circulatory System

The circulatory system is a system that circulates blood throughout the body and it is a very important part of the earthworm since the circulatory system basically makes up the body. The earthworm has a closed circulatory system which means the circulatory system consists of blood being closed in by blood vessels of different sizes; the blood is pumped by the heart through the vessels. There are three main vessels in the earthworm's body and those three vessels are the aortic arches, ventral and dorsal blood vessels. The aortic arches are sort of like human hearts to the earthworms and there are usually five pairs of aortic arches (hearts) which pumps the dorsal and ventral blood vessels. The dorsal blood vessels carry blood from the front of the earthworm's body and the ventral blood vessels carry blood from the back of the earthworm's body. This is basically how the Circulatory system of the earthworm functions.

Today's Objective

Today, we will observe the external and internal structure of the earthworm. We will find out the many different parts and segments of the earthworm. Carefully observe earthworm and observe which segments contain the aortic arches, seminal receptacle, crop, gizzard, etc.
Earthworm Anatomy