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Is this a valid project

Postby HopePressler1 » Sun Oct 07, 2018 12:36 pm

We recently discovered frog eggs in the pond in our back yard. We brought some eggs in to watch them develop. Now my daughter who is in first grade wants to complete a science fair project about the tadpoles. Her question is "Will tadpoles develop into frogs at a different rate in a tank inside our house or in the pond outside?" The variable she wants to change is the food. She wants to feed the tadpoles in the house "tadpole food" and the tadpoles outside will find their own food in the pond. The tadpoles in the house will have the same water as the tadpoles in the pond. My concern is that it will be impossible to control for all possible other variables outside - possibly water temperature, exposure to predators, etc.

Would this be an acceptable project even though there might possibly be variables she would not be able to control? Would a different question be better? If it isn't a valid project could you suggest a way she could complete this or a similar project?

Thank you,
ope Pressler

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Re: Is this a valid project

Postby 17eugenekim » Mon Oct 08, 2018 10:35 am

Hello and welcome to Science Buddies!

It's excellent that she is raising good questions and thinking about her experimental process, as well as the fact that you are concerned about the right aspects. I think this could be a valid project, but it may require some fine-tuning.

The first thing I want to point out is her "variable" (specifically, the "independent variable"). If her question is "will tadpoles develop into frogs at a different rate in a tank or outside," then her variable must actually be the environment - i.e. "tank or outside."

Here's the thing about that variable: as you were aware, it actually includes a lot of other variables. Food is one of them, as well as predator exposure, temperature, oxygen content, and a myriad of other things. Some of these could be better equalized if the tank was just put outside as well, near the pond, which would simulate weather/atmospheric conditions, as well as temperature. But a pond is a microcosm of its own, so there are still numerous other variables that we don't even know about that can be different.

Personally, at the K-5 level, I think this may be an acceptable project as long as there is an understanding of some of the other variables that could affect the results and could not be controlled. However, I am inclined to try and push it from "acceptable" territory into "good, clear" territory.

To do that, the easiest thing to do is set up two identical tanks and put them right next to each other. That way, you/she can dictate pretty much every condition down to the specifics. Admittedly, this does raise the resource cost of the project substantially. But from here, she can just pick any particular variable as her independent variable, change that, and measure how that affects growth rate. Temperature, water type/quality, air, type of food, light, population density, and acidity are some that I could just think of off the top of my head. There are surely plenty more, which you/she can research online for written articles!

Hope that helps. I'd be more than happy to answer further questions!

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