Earthworm

Earthworm Dissection Pre-AP Biology April 9, 2014 - Vu 3rd

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Lumbricus terrestris

The earthworm, Lumbricus terrestris, is part of the phylum Annelida. An earthworm is well-adapted to living in its life digging through soil. Its skinny shape allows the earthworm to easily maneuver through the soil. It also has a mucus coating which helps oxygen pass through its skin. The Earthworm passes through the soil while eating dirt in its way with the help of its muscular pharynx. As the food passes, sand grains in the gizzard help grind the food down which is then digested and absorbed in the intestine which runs down the rest or the earthworms body.

Objectives

In this presentation, you will learn the structures and functions of the digestive system in Earthworms. You will also learn the external and internal anatomy of Earthworms and their ecological roles.

Evolutionary Relationships of an Earthworm

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Earthworm Dissection - tutorial

Earthworm Dissection

Digestive System

An Earthworm’s digestive system is one of the most important features of the worm. It consists of mouth, pharynx, esophagus, crop, gizzard and intestine. When the Earthworm finds food the lips break the food down into smaller pieces since an earthworm does not have teeth.The food particles pass from the mouth to the pharynx where the food is lubricated by mucus secretions. This makes it easier to pass along to the esophagus. Next, the food is temporarily stored in the crop where they will get mixed together. From the crop, the mixture enters the gizzard where the actual digestive process begins.The powerful muscles of the gizzard churn and mix the mass of food and dirt. The mixture is reduced to a thick paste once the churning and mixture is complete.Next, the mixture is sent to the intestine. The intestine has friendly bacteria that eat the food mixture. Most of the worm’s body length is intestine.Finally at the end of the intestine, the soil particles and undigested organic matter pass out of the worm’s body through the anus.