Everything About Earthworms

Earthworm Dissection Vu Pap Bio April 8, 2014

Today's Objectives

To learn about the internal and external anatomy of the earthworm. Focus on the structures and organs of the earthworm and study the digestive and circulatory system. No earthworms will be eaten.

What is an earthworm?

The common earthworm or the Lumbricus terrestris, are invertebrates that belong to the phylum Annelida (segmented worms) because of their segments separated by internal partitions, digestive system with two openings and closed circulatory system. The word Annelida is derived from the Latin word annellus, meaning "little ring," refering to the appearance of the body segments. They belong to the class Oligochaeta due to their lack of appendages, few bristles and life on the land.

Life as a Night Crawler

earthworms have picked up the name night crawler because they are usually only out and about at night, and burrow in the earth during the day. They consume soil as they burrow, extracting nutrients from decomposing organic matter like leaves and roots. They transport nutrients and minerals from below to the surface when they defecate. Earthworms also leave tunnels for air to circulate through, so next time your gardening make sure there are a few earthworms in you soil.


Making the Cut

Digestive System

The digestive system is responsible for the intake, break down, and absorption of food. Earthworms have a digestive system that consists of the pharynx, which pumps food and soil into the tube called the esophagus. then the food moves into the place of storage, the crop, and then through the gizzard, where it is broken down into smaller pieces. eventually the food is absorbed farther in the intestine.

Fun Facts and Other Information

  • Earthworms are typically 7 or 8 inches long but some can get as big as 14 inches.
  • The average size of an earthworm is relative to that of a teacup.
  • Earthworms are indigenous to Europe, but are now found abundantly in North America and Western Asia.
  • The ring-like segments that make up the earthworm are called annuli.
  • The bristles that cover the annuli are called setae and help the worm to burrow.
  • Earthworms can burrow 6.5 feet deep.
  • They are hermaphrodites yet do not self fertilize.