Exploring an Earthworm

Abbey Boggs 4/7/14 Mitcham-PAP Bio-Period 6

Lab Objectives

In this lab, students will observe the external and internal structures of an earthworm.

Lumbricus terrestris

The earthworm is an invertebrate and is in the phylum Annelida. The earthworm resides in soil, which it helps fertilize. Earthworms are decomposers and thus are located towards the bottom of the food chain. Earthworms feed on dead and decaying matter, and are eaten by animals such as birds and rats.


Earthworms have adapted to living in the soil by having:

  • A mucus coating that aids in oxygen passing through the skin
  • A muscular pharynx that helps the earthworm clear soil out of the way
  • Sand grains in the gizzard that aid in grinding food

An Earthworm's Digestive System

Functions of an earthworm's digestive organs

1. Gizzard: The gizzard grind up food, which is aided by sand grains.

2. Crop: The crop provides temporary storage for food.

3. Mouth: The mouth obtains food for the worm.

4. Pharynx: The pharynx helps the mouth to suck in food and soil.

5. Esophagus: The esophagus is where food passes through to get to the intestine.

6. Intestine: The intestine chemically breaks down food using enzymes

7. Anus: The anus excretes wastes from the earthworm.

What does an earthworm's digestive system do?

The digestive system of an earthworm functions to absorb nutrients from soil that are essential to the earthworm's survival. When an earthworm sucks in soil, the material travels all the way to the gizzard, where the materials are then ground up by sand grains. After the food and nutrients have been digested, wastes leave the earthworm through the anus. The digestive system of an earthworm is closely related to an earthworm's muscular system, as the muscular pharynx and other muscles help the earthworm to obtain food and move that food along through the digestive system.

Human Impact and Influence

As pesticides and other chemicals are being commonly used by humans, soil in which earthworms thrive is becoming toxic. Eventually, that soil may become so toxic that earthworms can no longer live in it, which would lead to larger conflicts among the earthworm population.