User:Sasha A. Weitzman/Notebook/Biology 210 at AU

Identifying Algae and Protists

Introduction

---

Last week each group collected a small sample from their respective transect to create a hay infusion. This week, the sample was explored under a microscope to look for biotic life. A dichotomous key was used simultaneously, which follows a series of morphological questions to identify organisms. We used this method to attempt to identify unicellular prokaryotes and eukaryotes from two niches of the hay infusion. Prokaryotes differ from eukaryotes in that eukaryotes contain a membrane bound nucleus and more advanced organelles. In addition, there are two kinds of eukaryotes, algae, which photosynthesize, and protists, which consume nutrients to get energy. By observing the life forms in the hay infusion, each group can gain a better understanding of its hay infusion's ecosystem.

Methods

---

Initially, the hay infusion jar was retrieved and two wet mounts were made from two niches of the jar, in this case the top and the bottom. The wet mounts were made by pipetting a small drop onto the glass mount and covering it with a cover slip. The samples were then examined under a microscope and the dichotomous key was used when an organism was spotted. We were instructed to find 4 organisms, and record their characteristics such as shape, motility, size, etc. After 4 organisms were identified, in our case 3 due to time constraints, serial dilutions were prepared for next weeks lab, in order to allow bacteria to grow and to look at the hay infusions microbiology. To make a serial dilution, 4 tubes containing 5 mL of sterile broth were collected and labeled 10^-2, 10^-4, 10^-6, and 10^-8. 50 mL of the mixed hay infusion was then added to the first dilution (10^-2). The tube was then swirled, and 50 mL was added to the next dilution, and so on until each test tube contained 50 mL of the previous dilution, becoming more diluted each time. For this lab, two kinds of agar plates will be used to grow the bacteria. The first contains a regular nutrient agar, while the second contains tetracycline, an antibiotic. Four plates of each were obtained, labeled based on the dilutions (10^-3, 10^-5, 10^-7, 10^-9), and treated with it's respective dilution (10^-8 dilution was plated on 10^-9, and so on). It's important to start with the most diluted solution on the nutrient agar only plate to prevent contamination of both more concentrated bacteria as well as the tetracycline. The agar plates were then left to incubate until the next class.

Results

---

Notes on the Hay Infusion: Foul smell or mold and dirt. A thick layer of dirt was present at the bottom and a thin layer of potential mold (small dots) was seen just below the surface. The water was mirky with a light brown/green tint and residue could be seen on the wall of the jar. The green tint and residue on the top surface indicate potential life.

From the top layer, Euglena was observed, and had a green color indicating photosynthesis. The euglena was motile with a size of approximately 35-55 um. Chlamydomas was also observed with a rounder shape and 2 flagellum. These are considerably smaller than the euglena, measuring only about 7 um and lacked the green color of euglena. Finally, we observed Didinium, which were relatively large at 20 um. These were seen across the samples, but were not motile and did not appear to be photosynthesizing, indicating it could be a protist.

Discussion

---

This was the first step in looking at the organisms from the Hay Infusion. This gives more insight into what kinds of unicellular species live in our transect. Interestingly, more organisms were found on the top layer of the jar than the bottom. Furthermore, the euglena was found on the top surface, indicating that algae and other photosynthesizing organisms might be more successful attaining energy from the sun closer to the surface where there is more oxygen. After two months, one could predict that the top of the jar would be teeming with mold and algae. In addition, after two months, the variability of the infusion would greatly change. For this lab, we were only able to attain 3 species of organisms, potentially because the infusion only sat for a short time. After two months, a mini ecosystem would exist, potentially including predatory organisms such as amoebas or more species in the deeper parts of the jar. It could even contain entirely new organisms as the open jar interacts with bacteria in the surrounding environment. However, as resources within the jar become more scarce, I predict that photosynthesizing organisms would become more scarce as other organisms need their energy to survive. Eventually, this ecosystem would fail as a result of lack of sustainable resources. That being said, it is already clear that an ecosystem is forming. From looking at the euglena, one can see that it already meets the needs of life. The Euglena obtains energy through photosynthesis, is a unicellular organisms and therefore comprised of cells, is a eukaryote and therefore contains its DNA inside a membrane bound nucleus, reproduces asexually, and will eventually evolve.

References

---

Bentley, M., Knight, S., Zeller, N., Walters-Conte, K. 2015. Exercise II - Identifying Algae and Protists "Biology 210 Laboratory Manual" Freeman, S., Quillin, K., Allison, L. 2014. Biological Science (Fifth edition).

Examining Biological Life at AU (06/30/2015)

Introduction

---

Life can be seen all around us, from large organisms such as humans to the smallest organisms such as protists and other unicellular eukaryotes. As these different species interact with each other as well as the surrounding environment, ecosystems form which allow for evolution and natural selection to occur . Over time, natural selection creates biodiversity through the extinction of some species and the formation of others. In this lab, we will be looking at biodiversity through studying a small transect of land and it's containing ecosystem (Bentley, Knight, Walters-Conte, Zeller, 2015). Through this process, we will hopefully gain a better understanding of ecology as well as biodiversity.

Methods

---

This lab contained two projects, Initially, the class was divided into groups of 4 and told to find and describe a 20x20 meter transect of land on the Au campus. Transects were to be chosen based on the likelihood of biodiversity and high biotic and abiotic life. For this reason, we chose to conduct this research within a transect of land located between Hurst Hall and the East Quad Building, and next to Nebraska Ave. Next, we noted the nature of the transect and took a small sample containing soil and some biotic life (grass) for the second part of today's lab, the hay infusion. To make the hay infusion, we combined approximately 10 grams of our sample with 500 mL water and .1 g of dried milk. The jar containing the aforementioned ingredients was then shaken and labeled, then placed in the back of the room with the lid off.

Results

---

The area is relatively flat and is mostly comprised of different species of grass. In terms of biotic life, the transect also contains several trees, flowers, as well as life such as birds, squirrels, fungi growing adjacent to the trees, worms, and flies. In addition, our transect also contains a lot of abiotic life, through rocks, soil, buildings, the sprinklers for the grass, etc.

Discussion

---

This is the first part of an ongoing exploration of our transect. Most of this lab was devoted to finding and describing the transect as well as creating the hay infusion. In the coming weeks, the transect will be more closely studied, looking at the ecosystem from small organisms (protists) to larger invertebrates and vertebrates. In the next lab, we will be studying the organisms present in the hay infusion.