Observing Protists in Transect 5
The purpose of the experiment detailed in this notebook was to observe protists in a hay culture. The hay culture was made from a soil and vegetation sample taken from Transect 5, a certified wildlife habitat on the campus of American University in Washington, DC. Because of the site’s unique status, the expectation here will be to see a large amount of protest life in the sample. A large amount of biotic life should be observed if the site is planted specifically to encourage wildlife. The hypothesis for this experiment will be: If samples of a hay culture from Transect 5 are observed, then a large number of protists will be observed.
Materials and Methods
For this experiment, a 50 ml conical tube was used to take a soil and vegetation sample. Sample was collected from various areas around the transect, and comprised of ground mosses, grass, and topsoil. The sample was then mixed to combine components thoroughly.
In the lab, a Hay Infusion Culture was created using the soil sample. Eleven grams of the soil and vegetation sample were weighed and put into a large glass jar along with 500 ml of Deer Park water. To this, 0.1 grams of milk powder were added to the soil solution. The jar was then sealed, shaken to mix, then left uncovered for two days. After two days, a pipette dropper was used to pull samples from the culture. Samples were taken from the very top layer and from the bottom of the infusion, just about the solid layer. Specimens were observed at both 10x and 40x magnification using compound microscopes.
Data and Observations
After two days, the hay culture was showing clear signs of decomposition. The jar had a pungent rotting smell and pieces of vegetation were blackened and floating on the surface. A light scummy film had begun to coat the water surface as well (Figure 1).
Figure 1: Hay Infusion after 2 days
Under microscopic observation, however, there was a noted absence of life. The sample drawn from the top layer of the infusion did not contain any protists, although some plant cells were observed, though none were algae-based. The sample taken from the bottom layer returned slightly better results, with a few motile paramecium in evidence (Figure 2). These measured approximately 75 µm in length. Paramecium were identified with the aid of a dichotomous key.
Conclusions and Future Directions
The hypothesis was not supported by the evidence collected in this experiment. There was a noted dearth of living organisms within the hay culture, in spite of decompositional signs. It can be concluded that the infusion would have had more protist life present had it incubated for a longer period of time. If the infusion were left for two months, for example, rather than two days, protist life would likely flourish as decomposition would be more advanced and the protists would have more of a food source and more time to reproduce.
Paramecium are well suited for this environment, having all the components of life (energy consumption and use, a distinct cell wall, storage of information) and their mode of replication is unique in that it can be both sexual and asexual. In an environment like a two-month-old hay culture, organisms like paramecium would likely be numerous, while the soil and vegetation would be greatly degraded.
To improve the experiment were I to replicate it, I would leave the hay infusion to incubate for longer. I would also take a sample from the solid layer itself since the majority of life appears to be closer to the biological material there (close to the food source) rather than on the top layer.
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