Water Pollution Lab
Where present, amphibians such as frogs are often the first organisms impacted by changes to an
ecosystem. Pollution is one type of change that can negatively impact frog populations. In
ecosystems with pollution, frogs may display malformations such as missing or extra limbs or
digits, missing eyes, incomplete development, and other problems.
Metamorphosis is the process in which an animal’s body undergoes dramatic changes in form
during its life cycle. The three stages of frog metamorphosis include the egg, larva (tadpole),
and adult. Most malformations in frogs occur during the egg or tadpole stages of development.
This lab will demonstrate how chemicals in the environment may interact with chemicals within
tadpole bodies, changing the way frogs look after metamorphosis.
You will be given 4 encapsulated sponge animals and provided with 4 different liquids (bleach,
water, vinegar, oil). The encapsulated sponge animals represent tadpoles going through
metamorphosis. The different liquids in the beakers represent the natural ecosystem and the
various pollutants that can be found in the waters where tadpoles live.
Question: _______________________________________________________________
________________________________________________________________________
Hypothesis: _____________________________________________________________
________________________________________________________________________
Manipulated (Independent) Variable ________________________
Responding (Dependent) Variable
________________________
Procedure:
1. Obtain four capsules, four beakers, and plastic wrap from teacher.
2. Label beakers for each of the four test liquids.
3. Pour 250mL of each liquid its labeled beaker. Cover beakers with plastic wrap.
**Safety goggles must be worn at all times, you may not touch any of the liquids, do not
inhale any of the fumes.
3. Drop one capsule into each beaker.
4. Cover all beakers with plastic wrap again.
5. Record the start time on the data table.
6. Carefully swirl the beakers to make sure the capsules don’t stick to the sides.
**Do not put your fingers in the beakers!
7. Observe beakers for 30 minutes, recording observations at 5 minute intervals in the data table.
Watch for signs of metamorphosis (ex: capsule starts opening, when capsule is done opening,
color changes, bubbling, other changes etc.)
8. After 30 minutes, use the spoon to remove all capsules/frogs and place them in open Petri
dish for final observations. Cover the beakers with plastic wrap.
Data (see table)
Results: (summarize what happened in each beaker over the 30 minute period)
Water: ________________________________________________________________
_______________________________________________________________________
Bleach: ________________________________________________________________
________________________________________________________________________
Vinegar: _______________________________________________________________
________________________________________________________________________
Oil: ___________________________________________________________________
________________________________________________________________________
Conclusion: (was the hypothesis supported by the data? Why or why not?)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Questions
1. Your vinegar capsule should have completed metamorphosis very quickly once it started
opening. How do you think this would affect the adult frog in real life?
__________________________________________________________________
__________________________________________________________________
2. One capsule never opened at all. What would this represent in real life?
__________________________________________________________________
__________________________________________________________________
3. Which beaker represented an ecosystem that did not contain any pollution? Why is it
important to have a normal ecosystem represented in the experiment?
_________________________________________________________________
_________________________________________________________________
4. What problems might a frog with a malformation have trying to survive in the ecosystem?
_________________________________________________________________
_________________________________________________________________
5. If pollution levels increase and larger and larger numbers of frogs develop with
malformations, what impact could this have on the frog population?
__________________________________________________________________
__________________________________________________________________
Frog Malformation Data Table
0
5
Start
minute
Water
Bleach
Vinegar
Oil
30 Minutes
Water
Bleach
Vinegar
Oil
Final
Observations
10
minutes
15
minutes
20
minutes
25
minutes