Earthworm (Lumbricus terrestris)

Introduction - Earthworms prefer moist soil where it is not too dry or sandy. They are found all over the earth. They are chiefly nocturnal and come out of their burrows at night to forage. A good way to find them is to search with a flashlight around the rich soil of lawn shrubbery. The large night crawler is easily found this way, especially during warm moist nights of spring and early summer.

Materials - earthworms, paper towels, hand lens, glass, light source

Procedure - Write all responses on a separate paper that you will attach to this lab. A cover page must include your name, class, date and name of lab.

1. Place a sheet of paper toweling on your work and wet the center of the paper, leaving the rest dry. Place a live earthworm on the moist area. Observe its behavior. What happens when the worm contacts the dry toweling?

Does the earthworm have a positive or negative taxis to moisture? Why? (taxis - movement in response to a stimulus).

2. Place the earthworm on a paper towel which is completely wet. Observe the way the earthworm moves. Describe.

3. Place the earthworm on a piece of wet glass. Observe its movements. Does the smooth surface make a difference in the worm's movement? If so, why?

4. Place the earthworm on a moist towel and observe its motion. The earthworm's body wall contains well-developed layers of circular and longitudinal muscles, As it moves notice the progressing waves of muscular contraction. Do these waves move toward the head of toward the anus of the earthworm?

5. Hold the animals in one hand and lightly rub your fingers along its dorsal (back), lateral (side), and ventral (bottom) surfaces. On which parts do you detect the presence of small bristles (setae)?

Examine these setae with a hand lens. How many setae are on each segment of the earthworm?

How do you think these bristles function in earthworm locomotion, burrowing and resisting a robin's pull?

This process releases energy by oxidation of food molecules. The process of breathing involves taking in oxygen and releasing carbon dioxide. Organisms, like the earthworm, that require oxygen to release this energy are said to be aerobic.

1. Feel the surface of the earthworm. Is it dry or moist?

2. Observe the earthworm with the hand lens. Do you see any obvious respiratory organs?

3. Using your text or notes, describe how gases needed for cellular respiration reach the individual cells.

4. What is the relationship between the earthworm's taxis behavior regarding water and its respiratory mechanism?

This process involves the transport of materials within cells or between parts of a many-celled organism.

1. Using a hand lens, observe the dorsal (top) blood vessel extending along the back of the animal. What is the direction of blood flow in the vessel. (toward s the anus or the mouth)? The best way to see this is to place your worm in the top of a petri dish and invert the bottom over it, pressing gently. Using a hand lens and/or flashlight you should be able to see the pulsation.

2. Does the blood vessel seem to pulse? What do you suppose causes this?

3. What are the components of a circulatory system?

This process involves the control and coordination of the various activities of an organism.

1. Gently poke the posterior end of the worm. Then the anterior end. What type of response do you notice. What does this indicate about the structure of the earthworm's nervous system?

2. Shine a directed light on the earthworm. Describe the reaction of the earthworm to the light? Is this positive or negative phototaxis? How does this behavior relate to survival?

1. What activities and traits did you see in the earthworm that are characteristic of living things in general?

2. What characteristics of living things did you not see in this exercise?

3. Explain how the earthworm is adapted to its environment.

4. What is the scientific name of the earthworm? What does its name mean?

5. Beyond its use as bait to catch fish, how does the earthworm inadvertently serve human needs?

What unique anatomical features help it in its work? (Hint: Read the article that follows.)

6. Read In the Defense of the Lowly Earthworm and answer the following questions:

· Explain Aristotle's description of the earthworm as being "the intestines of the soil".

· Why did Charles Darwin equate them with a plow?

· Describe some of the factors that threaten the survival of an earthworm..

· Define: hermaphrodite, paleontologist, burrowing.

return home