Ogden Nature Center

Adapted from Shelburne Farms Project Seasons, Deborah Parella

Post-Visit Activity, All Grades 

Objective

Students will learn about earthworms through self-designed experiments and observation. 

Materials

• The materials for this activity vary depending on the kind of experiments the students choose to perform.  You might want to have on hand:  shoe boxes, containers of various sizes, plant misters, water, paper towels, flashlights, colored cellophane paper or cling wrap, hand lenses, different kinds of soil, thermometer, pieces of plexiglass, alarm clock, musical instruments, assortment of food scraps, different kinds of paper, and pencils. 
•    Worm Observation Worksheets 

Background

Students will discover some of this background information with their experiments.  This information is provided for the teacher's enrichment, and can be divulged to the students in conjunction with the activity if consideration is given to the experiments the students have chosen.  Don't spoil the thrill of discovery! 

There may be as many as 50,000 earthworms in an acre of ground, which means the worms in a pasture might weight more than the livestock grazing on it.  Earthworms are prized in the garden because they aerate the soil and recycle nutrients from organic materials to make fertile soil.  Under-appreciated, worms work day and night harrowing and fertilizing the ground.  Worms burrow 12-18" into the soil and bring subsoil to the surface by grinding it in their gizzard to a fine texture and excreting it.  This worm waste is called "castings". 

Worms move through the soil using stiff bristles along their bodies called setae, and muscles aligned both horizontally and vertically along their bodies.  To move, worms work their muscles alternately, first elongating the anterior (front) part, then flattening and constricting the posterior (back) part while the appropriate setae extend into the sides like anchors. 

If you cut an earthworm in half, the tail end will grow a new head, and the head end will grow a new tail.  You can determine which end is the front by giving it lettuce or other foot and watching which end pulls the food in.  Worms like moist, dark environs and though they have no eyes, they are very sensitive to light.  Worms can be paralyzed by too much light. 

Procedure

1. Have students collect and observe earthworms.  Ask them to bring them to school in a container filled with moist soil.  Discuss where they found their worms and share ideas about where worms live.  Ask the students to share one thing they learned about worms while observing them.  Brainstorm a list of things they would like to discover.
2. Divide the class into pairs.  Young classes might want to work as a class, or in groups with an adult helper per group.  Have them design an experiment to discover something new about worms.   Worm Observation Worksheets can be used to design and record experiments.  Younger students may need help brainstorming and designing experiments.
3. Remind students to practice good science etiquette.  They should take care to treat the worms gently and replace them in their soil containers as soon as they're done with the experiment.  Worms should ultimately be returned outside.
4. Before they begin, ask each pair to review their experiment design with you.  Help your students gather the necessary supplies.
5. Have the students perform their experiments and record the results.  Bring the class together to share and discuss experiments, methods, and results. 

Possible Worm Experiments 

• Do worms like it wet or dry?  Set up wet versus dry conditions on opposite ends of an otherwise similar container.  Place worms in the middle and record which way they go.  Do they stay in one place?  After 5-10 minutes, where are most of the worms?  Repeat this experiment several times with different worms. 
• Do worms prefer darkness or light?  Set up dark and light conditions in an otherwise similar container.  Place worms in the middle and record where they go.  After 5-10 minutes where are most of the worms?  Repeat this experiment several times with different worms. 
• Can worms see or sense different colors?  Examine the worm carefully with a hand lens to locate yes.  Can you find any?  Shine a bright light on a worm.  What is the reaction?  Cover the light with red cellophane and try again.  Any reaction?  Use different colored pieces of cellophane and record reactions.  Can worms sense colored light? 
• Is there a top and bottom to a worm?  Examine a worm carefully with a hand lens.  Note any differences in color, anatomy, and shape between present upper and lower sides.  Turn the worm over.  What happens?  Record reaction.  Repeat several times with this worm and others.
• Do worms have favorite foods?  What does worm poop look like?  Bury the food just below the surface of the soil and check periodically to see whether it is being consumed.  Keep track of those foods that disappear quickly and create a list of your worms' favorite foods.  Experiment with your own menu ideas, but NO MEAT.  Watch to see how the worm pulls food into his mouth.  Can you tell the difference between the worms' waste and the soil?  This experiment will take longer to complete.