The purpose of this experiment was to study the rate of phagocytosis of the specific protist known as Tetrahymena vorax. This certain kind of protist feeds at a normal rate when conditions are normal. We began the experiment of understanding how Tetrahymena feeds at normal temperatures. Doing so, we allowed the Tetrahymena to feed at specific time limits and then killed the protist with gluderaldheyde to detect how much the protist gained. We then counted how many food vacuoles were filled with India ink that was included in the environment of the Tetrahymena while the time was ticking.
We then constructed a similar experiment with different conditions to compare if the rate of phagocytosis was affected by the change in conditions. Comparing the two environments, we found that indeed the rate of Phagocytosis was affected by a change in environmental conditions. Introduction Tetrahymeha Vorax consist of freshwater protists that usually are oval shaped if not almost egg shaped. This organism belongs to a specific group known as the ciliates (Cambell). They use specialized feeding structures such as the Buccal Cavity to ingest their food into their oral cavity (Shefferly, 2010).
The Tetrahymena feed at different rates over time and can change with environmental variables. The food that is ingested into the Tetrahymena is contained in the food vacuoles inside of the organism. After the Tetrahymena has completed it’s feeding and the food vacuoles are filled, the digestion process then occurs. The digestion process has a certain type of organelle to invite enzymes to break down the food particles known as lysosomes. This then leads into the excretion of waste for the Tetrahymena.
Any food particles that were left undigested are then removed from the cell at a specific point inside of the cell called the cytoproct (Shefferly, 2010). Considering this process that the protist undergoes, we predicted that Cold temperatures could affect organisms by slowing down their metabolism. Reasoning behind this is that if any type of living organism is placed in a much colder environment nonetheless a different environment rather than normal, its functioning body processes, such as feeding behavior, will perform at a much slower rate (Curds).
We started out with examining the Tetrahymena feeding in normal conditions. India ink, which is the material the Tetrahymena fed on, was added to the Tetrahymena environment. We progressively timed the Tetrahymena as it performed phagocytosis. After the time was up, we examined how many food vacuoles were filled with the India ink to show how much the Tetrahymena had captured in the time limit given under normal conditions. These results of this experiment acted as a control for our next experiment we planned on performing.
The next experiment consisted of the same type of procedures of our control experiment but we changed the environment to a much colder environment by placing the Tetrahymena in an ice bath to see if the cold temperature affected the rate of phagocytosis. Before the experiment we hypothesized that a decrease in temperature will affect the Tetrahymena’s rate of phagocytosis. We also made predictions before the experiment in the context that if we placed the Tetrahymena in a colder environment, then the rate of phagocytosis would decrease. Materials and Methods
In the first experiment we were testing the rate of phagocytosis of the Tetrahymena, which would in turn be our control experiment. We first started off gathering 6 microfuge tubes for the experiment. We labeled them by the time limit each test tube would represent such as T0, T2, T5, T10, T20, and T30. We then inserted a chemical known as gluteraldehyde by a micropipette in the amount of 10ul into each test tube that was labeled. Next, we took the Tetrahymena that was provided to us from being grown in normal conditions in the amount of 3ml and 30 ul of India ink into a specfic test tube.
We made sure to start timing right when the mixtures were combined. Basically the T0 sample showed us that it was the base for comparing the different time limits because the time limit for that test tube was under a minute. As the time limit came to an end for that test tube, we took a sample of about 20 ul of the ink and cell mixture and inserted it into the labeled T0 microfuge tube, which contains gluteraldehyde. We also made sure to close the top so the suspension was not able escape. We proceeded doing that procedure for every other test tube.
We timed the other samples at 2 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes. Next, we set aside the 20 ul sample for after all of our timing was done to compare all samples. As we continued to wait for the timing of our samples we started to observe the Tetrahymena and how they were feeding on the India ink. By doing this, we placed living Tetrahymena and India ink onto a slide to examine under the microscope. We were able to observe how the Tetrahymena cells were performing phagocytosis and making movement.
We were also able to notice and pick out certain structures of the Tetrahymena such as the cytostome, and food vacuoles. We were able to complete all of the timed samples of the Tetrahymena and India ink and we proceeded to examine each individual sample under the microscope. We used a compound microscope to observe and gather data on the samples. We placed a single drop of the suspension of each microfuge tube on a slide to examine. We first moved the magnification lens to 10-40x and started to examine the food vacuoles of the protist.
We counted the number of food vacuoles that contained a black color, which was the India ink. Finally, after we gathered all of our data we placed our results in a graph. In the second experiment of the lab, we almost performed the control experiment verbatim but made a few changes to it. Instead of having the Tetrahymena tested in normal conditions, we tested the protist in a much colder environment by a sample into an ice bath and timing it while it sat in the cold environment. Another change we made compared to the control experiment was that we only used one sample instead of using all of the timed samples.
We specifically used microfuge tube T10, which we timed for 10 minutes. Our variables were different as well in this experiment by making time our independent variable, the number of food vacuoles filled with India ink our dependent variable, and our first experiment our control, which was Tetrahymena feeding in normal temperature. By performing these two experiments we were able to reveal how colder temperature feeding of Tetrahymena resulted in different data than that of in normal temperatures.
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