Earthworm Dissection Lab

By Aryeh Gruber

Objectives

Examine internal and external anatomy of an earthworm

Background Info

Earthworm (or Lumbricina) are members of the ringed animals or Annelida. There are approximately 1,800 species of earthworms worldwide. Earthworms do not have an internal skeleton as we do, and they do not have a protective hard exoskeleton as does an insect. They are flexible, long bundles of muscle, especially designed for life underground. Earthworms have specialized structures that help them live very successfully in their environment. Instead of having lungs to pump oxygen, they have five sets of simple hearts. Their blood flows close to their outer surface, absorbing oxygen and releasing carbon dioxide through a thin skin. Earthworms feed on organic matter in soil, and are eaten by birds, frogs, and turtles. Humans are also a predator of earthworms because of our need of earthworms for science

The Digestive System

The digestive system of an earthworm is made up by the pharynx, the esophagus, the crop, the intestine and the gizzard. Food 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. Next, 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.
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