User:Shraddha Batra/Notebook/Biology 210 at AU

February 8, 2014 Lab 2: Identifying Algae and Protists

I. Introduction In this week's lab experiment, titled "Identifying Algae and Protists," the primary purpose was to demonstrate how to use a dichotomous key and perform culture dilutions for bacterial growth. A dichotomous key is used to help identify organisms by examining and comparing different physical characteristics. By learning how to use a dichotomous key, we are able to examine organisms from our Hay Infusion culture, which was made last week from AU's community garden. This will help in our understanding of how organisms from different ecosystems are characterized. Additionally, dilutions of the cultures were made in preparation for next week's lab.

II. Materials and Methods Procedure 1: Hay Infusion Culture and Dichotomous Key

1. A wet mount of a given sample was made by placing a drop of the sample on a microscopic slide and covering it with a cover slip.

2. Organisms were examined under a microscope and identified using a dichotomous key. Size and physical characteristics were noted.

3. Additional slides of organisms were made from two different niches of the Hay Infusion culture by using a transfer pipette to place a drop of the culture onto a slide. A cover slip was placed on top of each slide.

4. Slides were examined under a microscope and identified using a dichotomous key. Size and physical characteristics were noted.

Procedure 2: Culture Dilutions

1. Eight agar plates were obtained, four nutrient agar and four nutrient agar plus tetracycline. The four nutrient agar plates were labeled as: 10^-3, 10^-5, 10^-7, and 10^-9. The same labels were added to the four nutrient agar plus tetracycline plates.

2. Four tubes of 10 mls sterile broth were obtained. They were labeled as: 2, 4, 6, and 8, respectively.

3. A micropipette set to 100 microliters was used to take a sample from the swirled jar containing the Hay Infusion culture.

4. The sample was placed in the sterile broth tube labeled 2. The tube was swirled.

5. The sample from tube 2 was placed in tube 4 and then swirled. Steps 4-5 were repeated for the remaining sample tubes.

6. 100 microliters from tube 2 were placed and spread on the 10^-3 nutrient agar plate and additionally on the 10^-3 nutrient agar plus tetracycline plates. This step was repeated for the remaining tubes and corresponding agar plates.

Observations and Data

-Appearance of Hay Infusion culture: The culture was divided into layers. The majority of the components was collected at the bottom of the jar. The bottom layer contained small leaves, small branches, soil, dirt, and rocks. The soil, dirt, and rocks resembled more of a sand-like texture. The remaining portion of the jar was liquid, which was less in amount than the week before, and it had a pale-yellow color. Additionally, a very thin film had grown at the top of the culture. The culture did not have any particular smell. -Samples were obtained from the bottom layer and from the above liquid layer of the culture. Organisms near plant matter would differ from organisms away from plant matter because organisms have different needs to survive, and some may rely on the plant matter while others may not need to; therefore, we would observe different organisms in the bottom layer containing the plant matter in contrast to the liquid layer. -Although we attempted to observe six organisms, three from each layer, we were only able to identify one organism despite obtaining a range of different samples on microscopic slides. The organism was found at the bottom layer of the culture, and it most closely resembles the algae Gonium. The organism was not mobile, and its size was approximately 100 microns. Since Gonium is an algae, it is photosynthesizing.

Figure 1: Gonium

-Needs of life: Because it is a photosynthesizing algae, Gonium can obtain energy from sunlight. The organism is a eukaryote so it contains membrane-bound parts. Gonium can process information, and it is able to undergo asexual or sexual reproduction. Through evolution, the organism is able to undergo greater cell specialization and complexity over time. -If the hay infusion culture had been observed for another two months, we would most likely expect to see more biotic organisms in the culture. The physical appearance of the culture may also change over time. It is also possible that some organisms may not be present over time if the conditions are not conducive to living. For example, lack of plant matter and water over time may affect some organisms that rely on it. -Selective Pressures: One of the factors that may have affected the composition of the sample could have been the temperature. The temperature at the time of sample collection was quite low, and the jar remained at room temperature which could have affected the presence of certain types of organisms in the jar. Additionally, the lack of sunlight may also have affected the presence of organisms in the sample. Some organisms are photosynthesizing, and the lack of sunlight in the jar affects the environmental conditions for them to live in.

Figure 2: Dilutions

Conclusion From this experiment we can see how an ecosystem with its organisms can change over time based off of its environmental conditions. The appearance of the Hay Infusion culture changed over the duration of one week, and certain factors affected both the location and presence of certain types of organisms in the jar; however, it was surprising that we were unable to find a diverse range of organisms despite the different conditions in the two layers of the jar. We can conclude that a dichotomous key can play an important role in identifying organisms. In procedure 2, we demonstrated how diluting samples will help in examining bacterial growth on agar plates. This will play a significant role in next week's experiment.

SB

January 31, 2014 Lab 1: Understanding Cell Specialization in Green Algae and Defining Niches

I. Introduction The title of this lab is "Understanding Cell Specialization in Green Algae and Defining Niches."There were two main objectives that were addressed in this dual-part experiment. In the first portion of this lab, the purpose was to provide an understanding of how organisms progress and develop over time. More specifically, three organisms of the Volvocine line were studied and their cells were analyzed to examine changes in complexity and specialization. The purpose of the second portion of this lab was to demonstrate the many components that constitute an ecosystem. There are various biotic and abiotic components in an ecosystem, and these elements were examined in a 20 by 20 foot transect (#4) of American University's garden. The following are the two hypotheses for the two experiments:

Hypothesis 1: The Volvocine line will show a progression of cell complexity among the three organisms studied.

Hypothesis 2: A study of AU's garden will reveal that there are a number of living and nonliving components of an ecosystem.

II. Methods and Materials Procedure 1: Understanding Cell Specialization in Green Algae

1. A drop of Chlamydomonas was placed onto a microscopic slide.

2. A drop of protoslo and a cover slip were added to the slide.

3. Organism cells were examined using a microscope under 4X, 10X, and 40X magnifications.

4. Cell number, colony size, and cell descriptions were noted.

5. Steps 1-4 were repeated for Gonium and Volvox.

Procedure 2: Defining Niches

1. Students arrived at the 20 by 20 foot transect (#4) of American University's garden.

2. Transect descriptions, biotic components, and abiotic components were identified and noted.

3. A sample of the transect was taken in a 50 mL tube. 50% of the sample was soil and the remaining 50% were materials found above soil such as leaves and plants.

III. Observations and Data Procedure 1 Data: Procedure 2 Data: -Description: The location of the American University garden was in a secluded area behind the campus, away from the academic buildings. The 20 by 20 foot transect was surrounded by 6 rectangular plots in which plants were growing. The land was moist due to recent rainfall, and most of the grass and plants were shriveled and dry due to the cold weather/season. Biotic and abiotic components included: leaves, tree branches, dry grass, dead flowers, little worms, soil, rocks, and wood chips.

IV. Conclusions and Future Plans As evident in the image of data for Procedure 1, the cells in the Volvocine line differed from one another. Beginning with Chlamydomonas, it is very easy to identify each individual cell. In is distinguishable from Gonium, which contains a colony of many cells clumped together, making it more complex than the individual Chlamydomonas cells. Continuing with this progression of complexity, Volvox appears as colonies that resemble large balls and consist of thousands of cells. Thus, over time in the Volvoine line we observe organisms undergoing greater cell complexity. Oftentimes, increasing complexity can produce benefits for organisms such as in the form of cell specialization. The observations in this portion of the lab are in agreement with the stated hypothesis. Other future studies could also examine the various factors contributing to increasing cell complexity.

In Procedure 2, we learned that an ecosystem consists of both biotic (living) and abiotic (nonliving) components. As a result, an environment and its elements influence how species exist. In the studied transect, there were few visible biotic elements due to the effects of cold climate. This may contribute to fewer organisms being found in the plant material sample about the soil, depending on the nature of the organisms. If this experiment were to be repeated again, the organisms within the soil should be further examined during daytime rather than nighttime. Data was taken at night; therefore, some elements may not have been identified due to low visibility. Overall, the observations support the stated hypothesis.

Excellent start on notebook. Clear and thorough notes describing tasks and context. SK