The Effect of Zinc on Worm Burrowing
By: Da’Jhane Gambrell-Sanders
Divine Savior Holy Angels High School
Abstract:
The purpose of this lab is to determine if earthworms are capable of detecting high levels of zinc in their
environment. In order to test this, worms were placed in the middle of four quadrants, each containing a
different concentration of zinc. The worms were then observed for twenty minutes to see which quadrants
they decided to burrow in. Our results show that the worms would burrow into a quadrant at random and
would remain inside that quadrant for the full time period. These results support the theory that worms
cannot initially detect harmful substances within the soil, which furthermore can have harmful
ramifications on our environment as well as the food chain.
Data Tables and Graphs:
Minutes Worm Spent in Each Quadrant:
Days
Introduction:
Environmentalists have made the argument that insects and other animals that reside in the soil are not
able to avoid chemicals used by farmers and manufacturers. An experimental lab was conducted at
Divine Savior Holy Angels High School to test this argument; a preference avoidance behavior lab. With
this lab, a environmental pollutant must be utilized. Zinc is a natural substance found in the environment
and is necessary for life and our environment. However, zinc in the environment has been rising
unnaturally due to human activities such as mining and steel processing. (Lenntech, 2016) Zinc is
beneficial for the human body to function in reasonable doses; however, high levels of zinc in the human
body are incredibly toxic and can lead to many health risks. Symptoms of zinc poisoning include: chills,
convulsions, fever, low blood pressure, vomiting, shock, and yellowing of skin or eyes (National Library
of Medicine, 2016). Therefore, because of this build up in the environment and its health risk factors,
zinc was used in this experiment. The lab that was conducted was that a worm is placed between two
lines of liquids; a line of water and one line of highly concentrated zinc. The experiment was conducted
to see if red worms were able to sense the liquids and make the safest decision and choose to cross the
water line. On all attempts with a different worm used in each attempt, the worms each chose the zinc.
Therefore, it was concluded from both experiments that worms are affected by chemicals in the
environment and they are not able to sense and avoid them. But will the results from the previous
experiments hold true when red worms are placed in a natural soil environment with multiple
concentrations of zinc? To test this, a lab was conducted using three different concentrations of zinc; 10
ppm, 100 ppm, 1000 ppm, and one control group of distilled water in four different quadrants of soil. The
locations of the worms will then be timed to see how much time they spend in each quadrant. If the
Earthworm is placed in the middle of these four quadrants over twenty minutes, then the Earthworm will
initially enter the medium and high concentrations of Zinc but will retreat and spend most of its time in
the lower concentrations because our second lab proved that the Earthworm was unable to recognize the
difference between the line of water and the line of zinc.
Materials and Methods:
Materials:
One pipet, Latex gloves, Safety goggles, Dissecting tray, Red worms, Potting soil, 10 ml. each of zinc
solutions of 10 ppm, 100 ppm, 1000 ppm, Distilled Water ,Stopwatch
Methods:
1. Gather all materials; divide lab tray into four quadrants using your finger and label each quadrant by
number as well as mark which quadrant will have which concentration of zinc or water as shown here
in Figure 1 (bottom Left) and Figure 2 (bottom right):
1. Place on goggles and gloves; distribute potting soil evenly amongst the quadrants
2. Take pipet and measure 10 ml. 10 ppm of Zinc into quadrant one (Reference Fg. 2)
3. Take pipet and measure 10 ml. of the 100 ppm of Zinc into quadrant two (Reference Fg. 2)
4. Take pipet and measure 10 ml. of the 1000ppm of Zinc into Quadrant three (Reference Fg. 2)
5. Take pipet and measure 10 ml. of distilled water into quadrant four (Reference Fg. 2)
6. Place the worm in the center of tray so that it is positioned in the middle of the quadrants
7. Record which quadrant the worm enters first and begin timer for twenty minutes
In those twenty minutes, record how much time the worm spends in each quadrant using your notebook
and pen
Quadrant 1 Quadrant 2 Quadrant 3
(10 ppm) (100 ppm)
(1000
ppm)
Quadrant 4
(10 ml. Water)
1
0 minutes 0 minutes 0 minutes
20 minutes
2
0 minutes 20 minutes 0 minutes
0 minutes
3
0 minutes 0 minutes 20 minutes
0 minutes
4
0 minutes 20 minutes 0 minutes
0 minutes
Results:
In this experiment, there are three types of variables. The first one is the independent
variable which include the different concentrations of Zinc in each quadrant. The
dependent variable was the amount of time the earthworm spent in each quadrant. The
control variables were the amount of soil in each quadrant as well as the amount of
solution in each quadrant. While on each day of experimentation the worms had the
choice of which quadrant to enter in, on days 2 and 4, the worms decided to enter into
Quadrant 2, which contained a medium zinc concentration of 100 ppm; to add to that, the
worm spent 50% of the experiment in this quadrant over the four days. Also, all of the
earthworms spent their 20 minutes in the quadrant they initially decided to burrow into.
Figure 1 below shows where the worm was placed at the beginning of each experiment
trial. One trend that was seen is that out of the four days of experimentation, the worm
spent time in three out of the four quadrants; these quadrants included the distilled
water, medium, and high zinc concentration quadrants.
Discussion:
To conclude, our data failed to support our hypothesis. We had originally thought that the worm would
enter the medium to high concentrations and then retreat to low concentrations. While we were correct
that the worm spent most of its time in Quadrants two and three, specifically 75% of experiment time,
however on each of those days the worm would spend the full twenty minutes in those quadrants
instead of moving to a lower concentration upon exposure. However, while our hypothesis was not
supported by our data, this lab was able to further prove that worms cannot initially sense pollutants in
the soil as they made no effort to avoid the high concentrations of Zinc. It would enter a quadrant and
stay consistently in that quadrant. In regards to possible errors in our experiment, we added less
solution, about 5 ml. of solution, in each quadrant which may have affected our results from day
one because 5 ml of zinc may not have been as potent on the worms as with a higher dosage. “Soil
pollution can negatively affect the metabolism of microorganisms and arthropods, which can destroy
some layers of the primary food chain and have a harmful effect on predator animal species. Also,
small life forms may consume harmful chemicals in the soil which may then be passed up the food
chain to larger animals, which may lead to increased mortality rates and even animal
extinction.” (Everything Connects, 2016). The pollutants can be passed on from consumer to
consumer throughout the food chain and can increase the concentration as move up into the higher
Trophic levels which could potentially affect our health, as well.
Further Questions:
Our experiment observed and tested whether earthworms can detect different concentrations of zinc in
soil and if they can, does that affect where they choose to live and burrow. After completing this lab,
one major question emerges; How does Zinc affect the worm’s bodily functions, specifically its
nervous system over a prolonged amount of time?
Works Cited
"Office of Dietary Supplements - Zinc." Zinc — Health Professional Fact Sheet. N.p., n.d. Web. 25
Feb. 2016.
"Soil Pollution." Everything Connects. N.p., n.d. Web. 25 Feb. 2016.
"US Environmental Protection Agency." US Environmental Protection Agency. N.p., n.d. Web. 25
Feb. 2016.
"Water Treatment Solutions." Zinc (Zn). N.p., n.d. Web. 25 Feb. 2016.