User:Nadia Khan/Notebook/Biology 210 at AU

Serial Dilution of Hay Infusion of Amphitheater Stream, July 2nd, 2015

Introduction: The goal of this lab was to familiarize oneself with identifying unknown unicellular eukaryotes using a dichotomous key as there are several different lineages. Understanding and identifying the algae and protists as well as their structural and functional differences was important in distinguishing them. Algae have the ability to photosynthesize while protists consume nutrients. Surveying the area for these organisms could relay to us information about the way that such environmental factors interact and the causes and effects that such bacteria have on the abiotic and biotic factors that exist in the transect.

Methods: Before beginning the serial dilution, two samples of the hay infusion from the stream was extracted from the top of the jar and two from the bottom and prepared on wet mount slides. They were analyzed under the microscope through 10x and 40x lenses and the eukaryotes on the slides were identified using a dichotomous key. Their sizes were recorded. Then, the hay infusion was shaken in the jar to begin the serial dilution. To begin this, 50μL of the Hay Infusion was added to 5mL of sterile broth. Then, 50μL from this dilution was then added to another tube of 5mL of sterile broth, making the substance more diluted. These steps were done twice more to achieve four tubes of diluted solutions, each at a different level of dilution- 10^-2, 10^-4, 10^-6, and 10^-8. Then, we prepared eight nutrient agar dishes in which four had tetracycline. A dish with and a dish without tetracycline were labeled 10^-3, 10^-5, 10^-7, and 10^-9. 50μL of 10^-2 solution were applied to the both of the 10^-3 plates and 50μL of 10^-4 solution were applied to both of the 10^-5 plates. 50μL of 10^-6 solution were applied to the 10^-7 plates and 50μL of 10^-8 solution to the 10^-9 plates. Lastly, the dishes were set aside to grow.

Results: The hay infusion was cloudy and had a white and green tint to the water. There was sediment at the bottom- it appeared as though there was a layer of sandy material. There were green, leafy particles at the top with a grimy film over part of it. There was a strong earthy odor to the substance. We were only able to identify three eukaryotes in the hay infusion. One of them was pandorina, one was colpidium, and the third was acetinosphaerium. There was numerous pandorina (50μm), a green algae, that was found at the top of the substance. They were very motile. There were several colpidium(30μm), a protozoa, found at both the top and bottom of the substance. Like pandorina, they were also motile. The last organism discovered was acitinosphaerium (25μm), another protozoa, found at the top of the hay infusion. The organism was very slow moving. Because the pandorina was an algae, it was able to photosynthesize, while the two other eukaryotes, being protozoa, were not able to.

Discussion: Unfortunately, only three different organisms were distinguished in the hay infusion. This lack of diversity in the sample could suggest that the sample taken was an inaccurate reflection of the transect or that the transect does not suit algae and protists well which is why there was a minimal number of different eukaryotes present. The organisms may have differed due to their distance from the plant matter because of the nutrients that the plants could provide to them. If they hay infusion grew for another two months, I would predict that the numbers of algae and protists in the sample would become less and less. Selective pressures such as lack of energy resources from food and the sun would play a role in their inability to survive.

Examining Biological Life at AU: Hay Infusion of Amphitheater Stream, June 30th, 2015

Introduction: The goal of this experiment was to understand how different organisms in an ecosystem are categorized and to familiarize oneself with observing niches in great detail, seeing natural selection play out as evidenced by the evolution of said organisms. The study of a transect, which is a land sample used to assess the vegetation patterns and animal population of a specific area, is effective in analyzing biodiversity and phylogeny. This in turn helped reach the goal of the experiment. The transect chosen was the stream next to the amphitheater on American University’s campus because of its important role on AU’s campus as a certified wildlife habitat. If there are several different biotic elements present in the transect, then all of these organisms bear traits that were selected for and prove the organisms’ fitness for this particular environment.

Methods: Upon arrival to the stream, we used a meter stick to chalk out a 20 m by 20 m space as the transect for our observations and sample collection. We observed the stream and its surrounding wooded area, taking note of the evident biotic and abiotic elements and photographing the ecosystem. Then we collected a sample of soil next to the stream that was reflective of the majority of soil in our transect and sealed it in a plastic bag. After returning to the classroom, 500 mL of Deerpark water was obtained and kept in a jar. Using a balance, 10 to 12 grams of the soil sample was measured and added to the jar. Again, using the balance, 0.1 gram of dried milk was measured and added to the water and soil mixture that was then shaken up in a now closed jar for 10 seconds. The jar was opened and after having been labeled, kept aside in the lab.

Results: Abiotic factors included water, sand, gravel, pebbles, stones and dirt in the stream. Surrounding the stream there was a sidewalk. Biotic factors included plants, grass, trees, and roots that bordered the stream. There was also a robin, house sparrows, and a gray catbird that flew over the transect. There was low traffic in the area with rarely anyone in the transect itself as it was a fairly isolated space among due to the heavy vegetation.

Discussion: The lack of human invasiveness likely proves beneficial to the ecosystem. After observing the site, there was evidence of a variety of organisms. This transect was an environment that could provide nutrients for several different organisms as they could flourish. They proved to coexist well. This could change due to availability of resources and thus competition due to overpopulation.