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Hi Jim, hope this helps...

Most earthworms are scavengers that feed on dead organic matter. They feed by passing soil through the gut, from which nourishment is extracted, or by eating organic debris, including leaves accumulated on the surface of the soil.

The digestive system is divided into a number of regions, each with a special function. Food that enters the mouth is swallowed by the action of the muscular pharynx, then passes through a narrow esophagus that has three swellings on each side. These are the calciferous glands that excrete calcium carbonate to dispose of excess calcium obtained in the food. The food then moves to the crop, which seems to serve only as a storage organ, and then to the muscular gizzard. With the aid of very tiny stones swallowed by the worm, the gizzard grinds the food thoroughly. Food is then digested by juices secreted by gland cells in the intestine. It is absorbed by blood vessels in the intestinal wall and from there distributed to the rest of the body.

Clams however, filter feed using cilia. They catch food in sticky mucus and move it into the mouth via cilia. However, they only retain some ability to filter-feed and rely on their bacterial symbionts that live within their gills for the major source of their nutrition. The symbionts receive nutrients and oxygen, which flow into the clam through the uppermost end of the shell.
3 years ago
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Asker's Rating:Asker's Comment:simple yet very informative. thanks[/CENTER]