Protozoan Lab

QUESTION: Our question was “What effect does the size of container have on the population of protozoans?

BACKGROUND: We had three jars; one control which was the size of the ones we initially used, one that was half that size, and one that was three times that size. They both had 1.2 grams of grass to 50 milliliters of water. We covered the jars starting on the second day. The experiment went on for 26 days, and we fully observed on 3 days. To try to make the test fair, we tried to do what made the most sense considering that there can’t be a small jar’s worth of grass and water in a big jar. We kept the ratios of grass and water simple and mostly proportional to the size of the jars. Also, when observing, we took observations from multiple

The green represents control or Jar 1, the orange represents the smaller jar or Jar 2, and purple represents the larger jar or Jar 3.

EVIDENCE FOR COUNTERCLAIM: However, it could be the amount of air exposure that affected the population and not jar size. Jars 1 and 2 had the same amount of air exposure, and their populations remained more similar than Jar 3 throughout the experiment. On the other hand, Jar 3 had about 2 more days of air exposure than the first 2 jars, which may be why Jar 3’s population was so high. This is also supported by the fact that in the late stage of the experiment, the jars had been covered for so long, and that could be why the populations decreased so significantly. REASONING: I think that the reason that the protozoans’ population was larger in the larger jars is that a larger jar is a healthier habitat for the protozoans. I think this is because the protozoans are more spread out in a larger jar, so they can be separated from fungi and other

Since Jar 1 and Jar 2 had an equal amount of air exposure and their populations were similar throughout the experiment, and their populations were much more similar than Jar 3’s, it may be that the extra air exposure in Jar 3 is what pushed its population to the top. To check this, I looked at the air exposure group. What I found was that even though the jar with the most air exposure had almost double Jar 3’s, the jar with no air exposure did even better, so I don’t think that it was air exposure that made Jar 3’s population