The Earthworm
Earthworms or night crawlers (because they come out at night to eat.), are the main contributors to enriching and improving soil for plants, animals and even humans. The worms make tunnels in the ground that allows air and water deep into the soil to make it enriched with nutrients. The worms eat the soil which contains organic matter such as decaying vegetation or leaves, which plants cannot use directly. After the organic matter is digested, the earthworm releases waste from their bodies called castings. Castings contain many nutrients that the plants can use.
Digestive System
The digestive system is separated into many segments, each with a certain function. Food such as soil or decayed plants and leaves, enters the worm's mouth where it is swallowed by the pharynx (a passage way from the nose or mouth into the esophagus). Then the soil passes through the esophagus, which has glands that release calcium carbonate to rid the worm's body of excess calcium. After it passes through the esophagus, the food moves into the crop (a temporary storage), where it is stored and then eventually moves into the gizzard (a part of the stomach that contains small stones to grind food). The gizzard uses stones that the worm 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.