User:Cassidy B. Hart/Notebook/Biology 210 at AU

7/2/2015 Exercise II - Identifying Algae and Protists

Introduction

All living organisms can be classified in to three domains; Bacteria, Archaea, and Eukarya. Eukarya are eukaryotes, meaning their cells have organelles and a membrane-bound nuclei. Bacteria and Archaea are both prokaryotes which means they do not have membrane-bound nuclei and organelles. Both prokaryotes and eukaryotes can be unicellular. The two large groups of unicellular eukaryotes are algae and protists. It is important to be able to identify these different organisms because they provide different roles in the environment; algae performs photosynthesis and protists consume nutrients. To identify the organisms in the previously prepared Hay Infusion (See 6/30/2015 entry) a dichotomous key is used. A dichotomous key consists of a series of two morphological questions that leads to the identification of the organism (Bentley, 2015). Using this key allows the unicellular organisms that populate the transect to be identified.

Methods

The Hay Infusion culture that was created last class was carefully brought over to the work area. The culture was then observed before two samples were taken from the culture. A sample was taken from the top and a wet mount was created by placing two drops on the slide and covering it with a cover slip. Using the same method, a sample from the bottom was also used to make a wet mount. These samples were then studied under a microscope and when an organism was spotted, a dichotomous key was used to identify it by answering the series of questions surrounding the organism's motion, shape, size, color, etc. Then nutrient agar petri dishes were inoculated with different concentrations of the culture. Four tubes of 10mLs sterile broth was labeled staring with 10^-2 and decreasing by a power of 2 for each tube. Four nutrient agar plates were also labeled starting with 10^-3 and decreasing by a power of 2. Finally four nutrient agar plus tetracycline plates were labeled with "tet" and also with 10^-3 and decreasing by a power of 2 for each plate. The Hay Infusion Culture was then mixed up and 100uL of the culture was added to the first tube, labeled 10^-2. 100uL from this tube was pipetted to the next tube and so forth until all the tubes were appropriately diluted. The serial dilution was then plated by pipetting 100uL from the first tube onto the nutrient agar plate labeled 10^-3 and carefully spreading it on the plate. This was then done for each agar plate and the corresponding tube and then again for the +tet plates. The agar plates were then placed agar side up in a rack to incubate at room temperature for five days (Bentley, 2015).

Results

The Hay Infusion Culture observations showed that it had a thin layer of a mold like substance growing on top of the water. There was also some leaves floating on top. The water itself was a murky brown/green and at the bottom there was a layer of sediment and some leaves that had sunk. The culture smelled musky and damp. On the top layer Pandorina of 50um were observed. There were lots of these organisms in the samples from the top and they were motile with green cells inside of them. Pandorina is a photosynthesizing green algae. Also on the top Actinosphaerium of 25um were observed. These are slow moving protists who do not photosynthesize. In the bottom sample, only one type of organism was observed. This was the Colpidium of 30um. Many of these motile protists were observed. They do not photosynthesize.

Discussion

The observation of only one organism in the bottom sample shows the low variability of the culture. This could be because it only sat out for 48 hours. If the Hay Infusion Culture was allowed to "grow" for another two months, the variability would greatly increase. However selective pressures could cause the bacteria who are best adapted for the environment to survive and reproduce, and so these bacteria would be most prominent. These selective pressures could be the amount of sunlight the culture gets, the temperature of the culture, or the food available to the bacteria in the culture. Certain bacteria could survive better in the different niches of the culture as well. This is because even though the culture is an ecosystem as a whole, the different niches provide different types of environment for the bacteria to grow in. For example, organisms closer to plant matter might be slime or water mold since they feed on decomposing matter such as leaves. In order to be considered an organism, it must have five fundamental characteristics; energy, cells, information, replication, and evolution (Freeman, 2014). An example of how an organism can meet all these characteristics is seen in Pandorina. Pandorina gets energy from photosynthesis, is a colony and so consists of cells, stores information in its nucleus since it is eukaryotic, replicates either asexually through mitosis or sexually, and finally has evolved since it is part of the volvocine line where Chlamydomonas is considered the origin of evolution (Bentley, 2015).

6/30/2015 Exercise I- Examining Biological Life at AU

Introduction

Biological sciences wants to understand life, especially the diversity of it (Freeman, 2014) This biodiversity is due to evolution, which occurs through natural selection and other methods. Natural selection is the process where the fittest organisms survive because they are best adapted to the environment and so survive to reproduce more, passing their genes along to the next generation. In this lab, the biodiversity of life is studied by observing a transect, or an ecosystem. The biome of the transect studied in this lab is temperate forest. Transects are important because they provide the opportunity to study the different niches and the organisms that habitat them within an ecosystem and see how all the unique biotic and abiotic factors interact. Biotic factors are the living components of an environment while abiotic factors are the nonliving components. Both play a crucial role in ecosystems and are studied in this lab.

Methods

To observe the transect at AU, a 20 x 20 meter area on American University's campus was selected. The area selected is located on the northern side of campus, in between the amphitheater and McDowell Hall. When looking down on the amphitheater, the transect is to the right and to the right of the transect is McDowell Hall. This area was then visited and observations were made about the biotic and abiotic factors. Pictures were taken of the area. A sample was taken of the soil and plants and placed in a large plastic bag. Eleven grams of the sample was then placed in a plastic jar with 500 mLs of deerpark brand water. 0.1 gram dried milk was added to the mixture and the jar was capped. The mixture was then shaken for 10 seconds, labeled, and put on the window sill to sit for 48 hours (Bentley, 2015).

Results

The selected transect consisted of trees, both big and small, with a stream running down the center of the transect. The stream was full of rocks along with sand. There was soil covering all the ground of the transect that was not the stream and there were bushes, ferns, weeds, and other plants. The transect was hilly, with the stream at the bottom and the land rising up on both sides of the stream. The biotic factors were the plants, trees, ferns, weeds, ants, and a few small birds. The plants and trees were spread around the stream, the birds were seen bathing in the stream, and the ants were seen crawling throughout the transect. The abiotic factors were the rocks, found in the stream, the water, dirt, air, and sand. The below images show the transect.

Discussion

The transect selected has multiple abiotic and biotic factors. These factors work together to provide habitats and food to the organisms that live in the ecosystem. In the observed ecosystem not many large mammals were seen and there is not much human traffic. However it is possible that deer or other mammals do visit this transect. This would be a good base for future observations. Another interesting question would be whether AU maintains the ecosystem at all since there was evidence of a sprinkler in the transect. If so it could change the natural environment.

References

Bentley, M., Knight, S., Zeller, N., Walters-Conte, K. 2015. Exercise I- Examining Biological Life at AU. Biology 210 Laboratory Manual

Freeman, Scott. 2014. Biological Science. Prentice Hall: New Jersey. 1.

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