Abstract
Have you ever heard the expression "a canary in a coal mine"? In the 1900's and earlier, coal miners brought canaries with them into the mines to act as early warning signals. The canaries were very sensitive to low levels of dangerous gases, so if the birds stopped singing, or got sick, then the miners knew to leave immediately, even if they felt fine. As it turns out, our froggy friends are also very helpful at signaling problems, not in mines, but in and around bodies of water. Try this environmental science fair project to find out how.Objective
To determine the percentage of malformed frogs in a local pond and determine if it is greater than what is expected for a healthy pond.
Introduction
So what kind of animal leaps up and surprises you like a jack-in-the-box, has a voice far larger than its size, and wears that Mona Lisa smile? The frog! These amazing amphibians, found from the tropics to the sub-arctic regions, transform themselves over their life cycle, from water-breathing tadpoles to mostly air-breathing frogs. In the folklore of many cultures, frogs are seen as clumsy and unattractive, but also as having transformative powers and hidden talents. (Remember the story of the frog that turns into a prince?) It turns out that the fairy tales have one thing right—frogs do have a special ability; one that is very important to humans. Frogs are an indicator species, which means they can alert humans to changes in the environment before humans are affected enough to notice the problems.
The frog's habitat of water and land, its metamorphosis from fish to frog, and its extraordinary skin are all responsible for its ability to act as an indicator species. For this science fair project, you'll focus on the skin, which is very thin and stretchy, kind of like a swimming suit. The most important feature of their skin, though, is that it's permeable to water and oxygen. This means that the skin allows water and oxygen to pass through, so frogs drink and breathe, in part, through their skin! When they are underwater, they can take in extra oxygen through their skin, and they don't ever need to drink through their mouths, because they can get all the moisture they need right through their skin, too. Frogs feel slimy because they secrete mucous that keeps their thin skin from drying out and helps prevent dehydration when the frogs are out of the water. Frogs must keep their skins moist at all times; otherwise, they won't get enough oxygen to survive. Frogs also shed their skin each week, in a process that looks a bit like dancing to "Twist and Shout." When they are done wriggling out of their skin, they eat it—frogs don't waste any bit of nutrition!
Frogs are very sensitive to changes in their water and land environments. Changes such as increased ultraviolet light (sunlight), pesticides or other chemicals, or parasites, can all contribute to errors in the frog's early development. When it is still a fertilized egg, cells and cell layers are "talking" to each other. These chemical conversations between the cells are what will form the parts of the tadpole, and then the parts of the frog, and they are controlled by genes.
![]() Click here to watch a video of this investigation, "Malformed Frogs by Susie and Katie." This video was produced by DragonflyTV and presented by pbskidsgo.org. |
In 1995, middle school students on a field trip discovered that one-half of all the frogs they caught in a pond in southern Minnesota had malformations. Historically, in Minnesota, the baseline percentage of malformations had been only about 0.2 percent (based on frogs collected between 1958 and 1963 and stored in the state's Museum of Natural History). The baseline is the normal percentage of malformations that you would expect to find in a healthy pond, due primarily to genetic defects. The children and their teachers alerted state officials that 50 percent of the frogs in their pond had malformations, and the story became national news and started a national evaluation of frog malformations. A report that was published 5 years after the children's discovery, showed that 44 states had found excessive malformations among 38 different species of frogs.
In this environmental science fair project, you will evaluate the percentage of malformations and types of malformations in your local pond, and help national researchers track and study the global problems affecting frogs and other amphibians. If you would like a preview of how to estimate frog malformations in your local pond, click the DragonflyTV video on the right and join Susie and Katie as they go frog hunting with their neighborhood friends.
Terms, Concepts and Questions to Start Background Research
Bibliography
This source describes the frog's amazing skin:
This source provides a field guide to all types of frog malformations, with anatomical checklists that may be helpful to more-advanced students:
This source describes the discoveries of the Minnesota middle school students in 1995, and describes how you can get involved in frog monitoring in your area:
With this source, you can use your science fair project to update national frog malformation databases:
This science fair project was inspired by this resource:
For help creating graphs, try this website:
Materials and Equipment
Experimental Procedure
| Type of Malformation | Limb | Spine | Head | Eye | Skin | Multiple Parts | Extra Parts | Total Count |
| Asymmetric | ||||||||
| Symmetric | ||||||||
| Percentage of malformations in the total number of frogs collected | Percent Asymmetric ______% | Percent Symmetric ______% | ||||||
| Percentage of Total Malformations ________% | ||||||||
Equation 1:
| % of malformations = | (number of asymmetric malformations) + (number of symmetric malformations) total number of frogs caught |
× 100 |
Variations
Credits
Kristin Strong, Science Buddies
Last edit date: 2008-12-30 10:38:00
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