User:Nicole Bonan/Notebook/Biology 210 at AU
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Sources of error
Sources of error
Revision as of 20:39, 6 July 2014
Lab 2: Identifying Algae and Protists
TA: Alyssa Pedersen
Lab Section: D01
July 2, 2014
The purpose of this experiment was to use a dichotomous key and a microscope in order to identify four organisms in the Hay infusion culture created in the previous lab. A serial dilution was then carried out in order to create samples of the culture that would be incubated in separate petri dishes of agar and tetracycline. It was hypothesized that if organisms existed near the top of the Hay infusion culture, then they would be able to photosynthesize, and that if organisms existed near the bottom of the culture, then they would be protists. In the following report, the methods used, results, data, and interpretation of the results of the experiment will be discussed.
Materials and Methods
First, a sample of the Hay infusion culture was taken from near the top of the culture using a disposable pipette. A wet mount was created using a drop of the culture sample, a drop of Protoslo, a cover slip, and a slide. The slide was placed under a microscope, and two organisms in the sample were observed and identified using a dichotomous key. The same procedure was then carried out using a drop of the Hay infusion culture taken from near the bottom of the culture.
Next, serial dilutions of the culture were made after swirling the Hay infusion culture to mix up all of the organisms in the culture. The first serial dilution was 10^(-2), which was created by adding 100µL of the Hay infusion culture to a test tube containing 100mL sterile broth. The next serial dilution was 10^(-4), which was created by pipetting 100µL of the 10^(-2) dilution into a separate test tube of 100mL of sterile broth. The third serial dilution was 10^(-6), which was created by pipetting 100µL of the 10^(-4) dilution to a separate test tube containing 100mL of sterile broth. The final dilution was created by pipetting 100µL of the 10^(-6) dilution into a separate test tube containing 100mL of sterile broth. A 100µL micropipette was used for all of the pipetting in the serial dilutions. A diagram of the serial dilutions is shown in Figure 1 below.
Figure 1: Diagram of Serial Dilutions of Hay Infusion Culture
The serial dilutions were then plated onto agar plates. 100µL of each serial dilution were pipetted, using a 100µL micropipette, onto separate agar plates and spread across the agar using a sterile glass rod. Then, separate 100µL samples of each dilution were pipetted onto separate agar plates that contained tetracycline and were spread across the agar using a sterile glass rod. All of the plates were covered, labeled with the initials of the lab members, and set on a windowsill to incubate at room temperature until the next lab. The tetracycline plates were also labeled with a "T".
After having incubated since the previous lab, the Hay infusion culture appeared to be about the same opaqueness as lemonade. There was sediment and plant matter at the bottom of the liquid, while the top of the liquid seemed relatively free of this type of matter. The liquid was a light brown color, and the matter at the bottom was very dark brown. The culture had an odor of algae and mildew.
Two organisms were identified from the top of the culture and from the bottom of the culture for a total of four identified organisms. The two organisms identified from the top of the culture were paramecium and amoeba. The paramecium was colorless and was the shape of an elongated oval. It had two vacuoles, a micro and macronucleus, and also had cilia surrounding its outer covering. The paramecium was 50µm long and was a protist. The amoeba had an irregular shape and was mostly colorless, except for the brown-green coloring that surrounded most of its numerous organelles. The amoeba also had a contractile vacuole that was constantly expelling water from the organism. The amoeba was 25µm in length and was a protist. The two organisms that were identified near the bottom of the culture in the sediment and plant matter were chlamydomonas and colpidium. Two chlamydomonas were observed in the same area; both were unicellular, colorless, and roughly cube-shaped. Both also had one pair of flagella, which were used to propel the organism in circular motions. The chlamydomonas were about 50µm in diameter each and were prokaryotes in the Domain Bacteria. Two colpidium were also observed near each other. Both were unicellular, colorless, and oval-shaped. Each organism was motile and had about six organelles. One colpidium was more motile than the other colpidium; this more motile organism tended to bounce around the other organism. At one point, the more motile colpidium seemed to engulf and then regurgitate the other. Both organisms were about 20µm in length and were protists.
Tables and Graphs
Figure 2: Image of Hay Infusion Culture
Table 1: Characteristics of Identified Organisms in Hay Infusion Culture
Figure 3: Illustration of Paramecium
Figure 4: Illustration of Amoeba
Figure 5: Illustration of Two Chlamydomonas
Figure 6: Illustration of Two Colpidium
Summary of BG info
The purpose of this experiment was to identify four organisms that existed in the Hay infusion culture prepared from the soil in Transect 5 at American University. The two organisms identified from the top of the culture were paramecium and amoeba; the two organisms identified from the bottom of the culture were chlamydomonas and colpidium. The hypothesis of the experiment was that if organisms existed near the top of the culture, then they would be able to photosynthesize, and if organisms existed near the bottom of the culture, then they would be protists. This hypothesis was made because it was believed that organisms near the top of the culture would have more access to light, while those at the bottom of the culture would have limited access to light and would thus have to create nutrients. However, the data from the experiment did not support this hypothesis. Both organisms that were taken from the top of the culture and also the colpidium did not photosynthesize; in fact, they were protists. The chlamydomonas, taken from the bottom of the culture, could photosynthesize. One possible explanation for why the data did not support the hypothesis is that the Hay infusion culture did not incubate long enough for a clear division between photosynthesizing organisms and protists to develop. Another possible explanation is that because there was so much plant matter in the culture, most organisms could just get nutrients from the plant matter instead of photosynthesizing.
Of course, there were sources of error in this experiment. One source of error was that the Hay infusion culture was moved across the lab in order for samples of it to be taken; during its transportation, some of the plant matter and organisms may have gotten mixed up in the culture, causing some organisms that would normally only exist at the bottom of the culture to be near the top of the culture and vice-versa. A way that this error could have been prevented would have been to take samples from the culture without moving the culture from the place where it had been incubating. Another source of error was lack of experience among lab members in identifying microorganisms. While lab members were diligent in determining the identity of organisms, the lab members may have misidentified certain organisms. This error could have been minimized by consulting with other, more experienced lab members in order to confirm the identity of the observed organisms. A final source of error was that
Lab 1: Biological Life at AU
TA: Alyssa Pedersen
Lab Section: D01
June 30, 2014
Natural selection is a major factor that causes evolution. The evolution of a species can create biodiversity, as a species can evolve different characteristics, splitting one species into two. Eventually, as natural selection continues, an entire ecosystem can be formed. An ecosystem consists of all of the abiotic and biotic factors in a certain area. Each organism has a niche, or a certain set of environmental requirements, within the ecosystem. An ecosystem can be divided into transects, which are just smaller areas of a larger ecosystem.
The objective of this lab was to observe the characteristics of a niche in a transect of the American University ecosystem and to create a Hay infusion culture from the soil in the transect. In the following report, the methods, results, data, and interpretation of the results of the experiment will be discussed.
Materials and Methods
First, a transect of about 20m x 20m at American University was observed. The area was noted as "Transect 5". Pictures of the transect were taken and notes about the abiotic and biotic components of the transect were written. Next, a sample of the soil was taken in a conical tube. 10g of this soil sample were then added to 0.1g dried milk and 500mL Deer Park water in a plastic jar in order to make a Hay infusion culture. The jar was labeled as "Transect 5 TJ NB".
The area that was observed, Transect 5, was a garden near the entrance to AU's campus. The transect was surrounded by paved sidewalks and was situated in a gully between two roads and a dorm building. The transect was hilly and had many biotic and abiotic components, most of which were landscaped and not naturally-occurring. Most of the biotic components were plants, and most of the abiotic components were stones.
Tables and Graphs
Table 1: Biotic and Abiotic Components of Transect 5
|Biotic Components||Abiotic Components|
|Birds||Rocks and Stones|
|Gnats||Clay, mud, and mulch|
|Spots of Mosses||Drainage ditch|
The above table includes all of the biotic and abiotic components of Transect 5 that were recorded. The biotic factors are listed on the left and the abiotic factors are listed on the right.
Figure 1: Aerial View of Transect 5
Figure 2: Transect 5, Image 1
Figure 3: Transect 5, Image 2
Figure 4: Transect 5, Image 3
Figure 5: Transect 5, Image 4
Summary of BG info.
The purpose of this experiment was to observe a transect (Transect 5) American University in order to learn about the types of biotic and abiotic factors in the transect, how they interact with each other, and how these interactions affect their niches. The result of this experiment was that many different abiotic and biotic components were observed in Transect 5 at American University. Most of the biotic components were plants, while most of the abiotic components were stones. The transect was landscaped and not naturally-occurring.
Sources of error existed in this experiment. One source of error was that the transect was only observed at one point on one day rather than multiple times over a longer period of time. Thus, observations about the transect only reflected that one point in time, so some outliers may have existed in the observations (for example, there may not normally be a bird in the transect, but as there was a bird in the transect at the time of observation, the bird was noted as one of the biotic factors). A way to overcome this error would have been to observe the transect multiple times over a longer period of time. Another source of error was that not every abiotic and biotic component was noted. A way to fix this source of error would have been to spend more time observing the transect and precisely identifying everything in it. A final source of error was that a soil sample was taken in only one small area of the transect, so it may not have accurately represented the majority of the soil and microorganisms in the transect. A way to overcome this error would have been to have taken multiple soil samples in the transect and compared them.
There were many implications of the data that was observed in Transect 5. One implication was that humans had shaped the land in order to suit their needs, and from there, an ecosystem was developed. For example, the drainage ditch that ran through the transect existed because humans needed a drainage system to conduct water away from roads during storms. The area around that drainage system was then landscaped in order to look appealing to humans. The landscaping included plants and trees, which helped to create an ecosystem for birds and insects in the area. Another implication of the data was that Transect 5 had very nutrient-rich soil in the areas where plants and trees were growing. These species were leafy and healthy, which indicated that they were getting the nutrients and water needed to sustain themselves. A final observation of this experiment was that the transect was very clean and organized, in that plants were planted in specific areas and there were few weeds that seemed to be growing randomly throughout the transect. The implication of this observation was that the niches of many species within the ecosystem was controlled by humans; humans decided where plants would be planted, and they worked to get rid of unwanted weeds.
The results of this experiment could be used by others to observe the difference between natural and artificially-created ecosystems.
This experiment applies to real world issues