Purpose/Introduction- Through doing this experiment, I hope to confirm my ideas concerning the effect of various water temperatures on a Daphnia’s (or sea flea’s) heart rate. Based on background information and previous knowledge, I hypothesize the following: “If the temperature of the daphnia’s water increase, then its heart rate will increase similarly.” Initially, my hypothesis was based only on the fact that heat caused molecules to move more quickly. However, upon further research, I came to learn that the daphnia is a cold blooded animal, meaning its body does not perform thermoregulation. Therefore, increased temperatures affect body functions directly. With this given information, I can infer that the higher temperature will increase heart rate in order to keep up with the rapid internal reactions.
Procedure- The first step we took in testing our hypothesis was acquiring a daphnia. We did so by using a small pipette, a suction tool we inserted into a small jar of daphinas. We sucked water into the pipette, along with the largest daphnia available. While keeping the daphnia in the pipette, we constructed a slide to hold it. By putting a tuft of cotton into a slight crevice within a piece of glass, we were able to place the daphnia in the slide. Making sure the daphnia was immobilized by the cotton, but breathing in its limited water, we placed another non-creviced slide atop the daphnia, holding the two pieces together with rubber bands. With the daphnia secure within its slides, we proceeded to begin creating the different water temperatures in which we would observe the daphnia’s heart rate. Letting one glass bath sit out, in order to obtain room temperature water, we simultaneously boiled water for hotter temperatures. When room temperature was achieved ( 26 degrees Celsius) we placed the slide in the bath, gave it several seconds to acclimate, moved the bath onto the microscope’s stage and, using medium power, counted its heart beats in 10 seconds. Multiplying the result by 6, we recorded the daphnia’s Heart Rate per Minute. After recording heart rate at room temperature, we used ice cubes and hot plates to raise and lower the water temperature. By the experiments end, we had recorded heart rates at 13, 26, 33, and 38 degrees Celsius. Daphnia Heart Rates at Various Temperatures(Table #1) | Temperature(Degrees Celsius) | Heart Rate(Beats per Minute) | 13 Degrees Celsius (Coldest) | 80 BPM | 26 Degrees Celsius(Room Temperature) | 156 BPM | 33 Degrees Celsius | 210 BPM | 38 Degrees Celsius (Hottest) | 270 BPM |
Discussion- Through the procdeures of my experiment, not only had I fulfilled my purpose, but I proved my hypothesis correct in the process. My data clearly shows that a steady increase in water temperature would contribute to a more or less equal rise in the heart rate of the daphnia. Between each measured temperature, there is about a 7.6 increase in BPM for every degree the temperature rises. While the data may speak for itself, there are other pieces of evidence which further prove my hypothesis correct. For instance, the fact that no variables had changed between the times we observed the daphnia other than temperature further attests to the truth of my original hypothesis. While obvious, this simple fact shows that it was completely the result of the water temperature altering the heart rate, and that no other variables, such as foreign chemicals, were tainting the results. My