How Cardboard Effects Oxygen Consumption in Yeast

Purpose; To examine the effects of oxygen consumption that cardboard as a biodegradable pollutant has on yeast using a series of four systems with methylene blue, water, yeast and cardboard.

Method; Dilution Series


1. Go through the dilution series 4 times so that you end up with 4 test tubes with 1/27 of a drop of methylene blue (20 drops of yeast each)

2. Blend a piece of cardboard with water to place in the test tubes

3. Do the same dilution series with cardboard as we did for the methylene blue in to the 4 test tubes. So the 4 amounts in each test tube are the cardboard levels we will be testing.

4. Wait to see how well the yeast mixes with each amount of biodegradable pollutants (cardboard)



In conclusion, we made 4 systems all with 1/27mL methylene blue and 20 drops of yeast. The first system had 1mL of cardboard diluted with water; the second had 1/3mL; the third had 1/9mL and the fourth had 1/27mL of cardboard and water diluted.

We found that our experiment was successful because the water was clear at the end, therefore the cardboard fed the yeast and caused growth.

If we were to redo our experiment, we would put a little less yeast in it (15 instead of 20), because there was a lot of yeast left over at the bottom of the test tube. Even though it worked really well, this could make it better.

The big issue we had was that we had to redo the experiment because we couldn't figure out how to dilute the cardboard with water.

Something we could do for an extension is use saltwater instead of freshwater because most of earth's water is saltwater (96.5%). So by seeing the effects that the cardboard has on the saltwater, the information would be more useful to real life. We could also try it on a larger scale because then we would know if a larger amount cardboard would cause any different affects on the water.

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