Pollution and Malformations Lab Names: ______________________________________________________
The three distinct life stages of amphibians include the
1. egg, 2. larva, and 3. adult. The larval stage for toads
and frogs is called a tadpole. A tadpole changes into an
adult frog or toad through a process called
metamorphosis. This process is one of the most
spectacular and important events in the life cycle of
frogs and toads. Depending on the species and
environmental factors, metamorphosis can occur very
quickly or very slowly.
Northern Leopard Frog with two extra back legs
Human activities affect metamorphosis. For example, water pollutants disrupt the normal chemistry involved in
tadpole development. These disruptions can cause the frogs’ and toads’ legs to grow too long or too short.
Some frogs and toads may not grow all 4 legs and others may grow more than 4 legs. For example, in Ontario,
Canadian ecologists found leg problems in frogs because of the chemicals the farmers were using on their crops.
The farmers contaminated the water where the frogs live and that pollution caused the process of
metamorphosis to go all wrong.
In your lab you will see the effects of pollution just as frogs do when they go through metamorphosis.
Yesterday, I put four capsules in four different liquids: water, vegetable oil, rubbing alcohol, and vinegar. The
capsules represent your tadpoles. The capsules’ directions told me to put the capsules in water, which will
dissolve the plastic covering and allow a sponge-like animal to grow. This is much like how metamorphosis
occurs in frogs but what happens if the water is polluted with other chemicals?
You are going to look at four frogs that grew in one of the following liquids: clean water, vegetable oil, rubbing
alcohol, and vinegar. Answer the questions below before looking at them.
1. According to the article you read above, what is metamorphosis?
2. What is your hypothesis for the water?
3. What is your hypothesis for the vegetable oil?
4. What is your hypothesis for the rubbing alcohol?
5. What is your hypothesis for the vinegar?
Now look inside each cup and observe the results of the pollution.
6. Which hypotheses were valid? null?
7. Write a paragraph 4-6 sentences long that describes how pollution can affect organisms. Your
paragraph must have a topic sentence and a concluding sentence. Make sure to reference these lab
results. This is your conclusion for the lab.