Name _________________________
Date Due ______________________
Title: Extracting Earthworms
Introduction:
After a heavy rain, it's not uncommon to see swarms of earthworms wriggling on the street and
sidewalks. Even when tilling the soil or just digging a hole, you're almost guaranteed to see an
earthworm or two.
Would it surprise you, then, to know that Wisconsin has no native terrestrial earthworms? If there ever
were native earthworms in the Great Lakes region, they were killed thousands of years ago when
glaciers covered the area. All of the earthworms commonly seen today are non-native species, most of
which were introduced to the region by European settlers.
Not only are these earthworms exotic, they are also classified as invasive -- meaning they are likely to
harm the environment and displace native species. For instance, the ecology of northern forests often
depends on a thick layer of leaf litter remaining on the ground throughout the year. Earthworms
remove that leaf litter by converting it to topsoil—and that seemingly benign action can so completely
change the chemistry and biology of the forest that native plants and trees are no longer able to grow
there.
Learning Target:
 Explain why earthworms are considered an invasive species to Wisconsin. (knowledge)
 Hypothesize ways in which invasive species such as earthworms change the movement of
nutrients in an ecosystem (reasoning)
 Compare data gathered from two different environments- a forest and construction site. (skill)
Materials:
For each team of researchers (usually a group of 3)
 1/3 cup (40g) of ground yellow mustard mixed with enough tap water to almost fill a gallon jug
 1 length of string 1.2m (4 feet) long
 Water container for rinsing worms
 Paper plate with moistened paper towel for observing and counting worms
 Forceps
 Pencil, lab sheet, and clipboard
Safety:




Wear clothes appropriate for the outdoors and inclement weather- long pants, closed shoes.
Stay with the group and avoid going off of the trails. (There is poison ivy in the Nature Pod)
Treat all living organisms humanely.
Don't get mustard in your eyes, as it can be very painful. If you do, flush the eye with plenty of
water. Do not pour the mustard solution directly on worms, as it is an irritant to them.
Problem: Does human activity influence populations of earthworms?
Hypothesis: __________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
Procedure: Bringing Up the Worms
Work as a team of 3 students:
 Worm extractor (marks out area, pours mustard solution)
 Worm gatherer (removes worms from study area as they emerge, rinses worms, places worms
on damp paper towel)
 Worm counter and recorder (reads directions, counts worms and records data)
Before leaving the room.
1. Prepare the extraction solution by place 1/3 cup (40g) of ground yellow mustard in a milk jug.
2. Add water to the jug until it is about 3 cm from the top.
3. Close the jug tightly and shake it until the contents are thoroughly mixed.
4. Determine jobs and gather supplies. (See materials list)
At the test site:
1. Using the string, measure off a square of soil about one foot (30
cm) on each side for your study area.
2. Slowly pour the mustard solution over the soil inside the
boundaries of your study area. Pour it so it soaks into the soil
instead of running off the soil. Stop when the solution will no
longer soak in. The worms will start coming up. Don't worry;
the mustard irritates their skin and makes them escape to the
surface, but it does not harm the worms.
3. The first worms to emerge will be very tiny- maybe only a cm
long so pay close attention. Let the worms completely emerge
before you pick them up or they may go back into the soil.
4. Gently pick up the worms with a forceps or your hands and dip them into a container of fresh
tap water to rinse off the mustard solution. Now lay them on a wet paper towel. Do not count
centipedes, millipedes, pill bugs or any other organisms that emerge. Only count worms that
emerge in your boundary.
5. Continue to slowly add mustard solution making sure it stays in your boundaries until it is all
gone.
6. Record your final count of worms in the data table.
7. Complete the observation table for the site.
Caution: The worms are "breathing" oxygen through their wet skin, so they must be kept moist
at all times. Worms are fragile animals and can be hurt easily, so handle them very gently.
8.
When you are finished extracting and counting worms return them to an area outside of your
test plot.
Data:
Site 1- Nature Pod- Forest
Group Total
Class Total
Class Average
Observations
Outside temperature
Description of
extraction area
Site 2- Construction Site
Group Total
Class Total
Class Average
Observations
Outside temperature
Description of
extraction area
Data Analysis:
Skill
1. According to the class totals, at which site was the greatest number of earthworms extracted?
__________
2. Hypothesize a reason for the results. ________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3-6.
7-12.
Calculate the surface area of the test plot. (SHOW YOUR WORK!- formula used, correct values
substituted, correct answer, correct units)
Calculate the amount of surface area per worm for each site. SHOW YOUR WORK!- problem set
up, correct answer, correct units.)
Forest
Construction Site
Conclusion:
Knowledge
1. Why are earthworms considered an invasive species? _________________________________
______________________________________________________________________________
______________________________________________________________________________
2.
What other invasive species actions were analyzed in the lab? ___________________________
Reasoning
3. How are the actions of earthworms affecting the movement of nutrients through the school
forest?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4.
How are the actions of humans at the construction site affecting the movement of nutrients
through the athletic fields?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
5-6. Does human activity affect populations of earthworms? Explain. ____________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________