09/29/19 Biology I - Period 7/8 Lab Report - Daphnia Heart Rate Problem Definition: This report centers around the experimentation of Daphnia, small organisms with clear and visible organs who are able to react in such a way that is expressive of the environment they are in. Our job was to investigate how different water temperatures would affect the heart rate (BPM) of Daphnia. Our variables are reflective of our needs for this project. Our independent variable was of course, the temperature of the water we were testing our specimen in. (These temperatures, as we later discover turn out to be for 15 celsius for cooled water, 22 celcius for room temperature water, and 33 celsius for heated water). Meanwhile, our dependent variable, was in turn, the average heart rate of our specimen after being placed in the exact temperature of the water. We ran five trials with such intentions. Our hypothesis reads as so - We predicted that if water temperature alters whilst the specimen,( in our case - the Daphnia) is located in it, then cold water (15°C), will decrease it significantly from the controlled heart rate (at 22 °C - room temperature water) and hot water (33 °C) will increase it significantly from the controlled heart rate of (22 °C - room temperature water). This is because not receiving enough heat will slow the heart down to conserve energy, whilst overheating requires the body to generate energy to cool itself off and increases the heart rate to accomplish so. What sources this claim is the ability of the human body to regulate homeostasis when faced with temperature changes. Taking these observations, we applied them to our predictions and proceeded to run such trials with results to confirm or not confirm in mind. Experimental Design: The design of this experiment was structured in such a way to accommodate the findings of the results we required to test our hypothesis. We had a precise procedure to use - with set materials, control aspects - and a clear definition of independent and dependant variables. Independent Variables: The temperature of the water used to maintain the Daphnia in - 15°C for cooled water, 22°C for room temperature water, 33 °C for heated water. Dependent Variables: The heart rate (BPM) of the Daphnia after being placed in cooled water, room temperature water, and heated water. Control: The average heart rate of Daphnia when observed in room temperature pond water. Constants: - Beats to time test ratio - Equipment used - Liquid type - Trials ran Materials: - Live Specimen (Daphnia) - 5.3 ounce Chobani Yogurt Cup - 40 mL beaker - Faucet (to obtain heated water) - Glass Coverslip - Ice Cubes - Indented Slide - Microscope - Observation Sheet - Pencil/Pen - Pipette - Room Temperature Pond Water - Timer - Thermometer Room Temperature Trials : 1. Obtain a 40 mL beaker 2. Fill the beaker with room temperature pond water to the 20 mL line. 3. Measure the temperature of the water (using celsius) 4. Use a pipette to grab the specimen (Daphnia) from the designated jar 5. Gently squirt Daphnia into indented slide (which holds the room temperature water) 6. Cover with glass coverslip 7. Place indented slide onto microscope stage. 8. Locate heart of Daphnia 9. Count and record heart beats per 15 seconds (Multiply for BPM results) 10. Repeat until all five trials are complete Cold Temperature Trial : 1. Remove indented slide from microscope stage 2. Obtain the 5.3 ounces Chobani yogurt cup 3. Fill cup halfway with water and place ice cubes in 4. Use pipette to grab Daphnia from indented slide and place it into a beaker of pond water 5. Place beaker into cup 6. Wait until the temperature of the water in the beaker is 15°C. 7. Use pipette to grab Daphnia and place onto indented slide (containing cooled water) 8. Cover the slide with a glass slip 9. Place indented slide onto microscope stage 10. Locate heart of Daphnia 11. Count and record heart beats per 15 seconds (Multiply by 4 for BPM) and record 12. Repeat until all five trials are complete Hot Temperature Trial: 1. Remove indented slide from light microscope stage 2. Obtain a 5.3 Chobani yogurt cup 3. Fill cup half way with warm tap water (dump a bit of water out if it gets too cool and add more hot water) 4. Place beaker into cup 5. Wait until the temperature of the water in the beaker is 33°C 6. Use pipette to grab Daphnia and place onto indented slide (which contains heated water) 7. Cover the slide with a glass coverslip 8. Place indented slide onto microscope stage 9. Locate heart of Daphnia 10. Count and record heart beats per 15 seconds (Multiply for BPM results) 11. Repeat until all five trials are complete Data: Room Temperature Trials (15 °C) Trial Temperature Beats- 15 sec BPM #1 22°C 47 beats 188 beats #2 22°C 43 beats 172 beats #3 22°C 46 beats 184 beats #4 22°C 42 beats 168 beats #5 22°C 44 beats 176 beats Average beats per 15 seconds in 22°C water : 44.4 beats Average beats per minute in 22°C water : 177. 6 beats Room Temperature Trials (22 °C) Trial Temperature Beats - 15 sec BPM #1 15°C 34 beats 136 beats #2 15°C 36 beats 144 beats #3 15°C 35 beats 140 beats #4 15°C 35 beats 140 beats #5 15°C 33 beats 132 beats Average beats per 15 seconds in 15°C water : 34.6 Average beats per minute in 15°C water : 138.4 beats Heated Temperature Trials (33 °C) Trial Temperature Beats - 15 sec BPM #1 33°C 50 beats 200 beats #2 33°C 51 beats 204 beats #3 33°C 50 beats 200 beats #4 33°C 52 beats 208 beats #5 33°C 49 beats 196 beats Average beats per 15 seconds in 33°C water : 50.4 Average beats per minute in 33°C water : 201.6 beats Conclusion: The conclusions that can be drawn from this experiment are evident. The hypothesis we presented at the beginning of our experiment is valid and supported by the evidence we have gathered. (We predicted that if water temperature alters whilst the specimen,( in our case - the Daphnia) is located in it, then cold water (15°C), will decrease it significantly from the controlled heart rate (at 22 °C - room temperature water) and hot water (33 °C) will increase it significantly from the controlled heart rate of (22 °C - room temperature water). This is because not receiving enough heat will slow the heart down to conserve energy, whilst overheating requires the body to generate energy to cool itself off and increases the heart rate to accomplish so). T he difference between the water temperatures and the heart rate averages supports our hypothesis. The cooled water, at 15 °C, was 7 degrees cooler than the constant temperature, whilst the heated water, at 33 °C, was 11 degrees warmer than the constant temperature. The constant temperature maintained at 22°C. When under constant temperature (room temperature), the Daphnia’s heart rate remained at a rate of 177. 6 beats per minute. However, when exposed to cooler temperatures (15 °C), the Daphnia’s heart rate slowed to 138.4 beats per minute. That lowered the BPM of the Daphnia by 39.2 beats. Afterwards, the trial was run with heated water (33 °C), which increased the Daphnia’s heart rate to 201.6 beats per minute. This was 24 beats above the control. Using this found data, one can conclude that the increase of water temperature is directly correlated with the increase of Daphnia BPM. I believe our drawn conclusion is valid. Our hypothesis is supported by our data, with the average Daphnia BPM of cooled water being under the average Daphnia BPM under room temperature water, whilst the average Daphnia BPM under heated water being above that. We used precise constants such as water type, compared to a control, and took great care to record data at the most precise time intervals. Our independent variable directly impacted our dependent variable in the way we predicted it too. All aspects of the experiment were controlled and monitored. Although not perfect, the lab was carried out with minimal interference and turned out to be very successful. While our experiment was conducted with great precision, there are many minor yet impact details we must examen. While I believe that our conclusion is valid, it can certainly be improved upon. The amount of trials we did were nowhere near enough to how many could have been done to truly capture the most precise intervals of change in the experiment. Occasionally, we would have to restart a trial due to human error, which would prolong the exposure of different water temperatures to the specimen. This added stress of increased time spent could have easily been a part of the reason our results developed the way they did. Other aspects out of our control also may have affected the results taken from such an experiment. For example, the sudden passing of our first specimen after it had given birth under the microscope could easily be taken as an outside factor that impacted the experiment. The use of two different creatures could have easily been a large aspect of the impacted data. If we were to run the lab through once more, I believe we would be much more likely to find more precise conclusions if we could spend more time on running more trials, making sure our timing is as constant as it should be and picking reliable specimen. All that being said, I did thoroughly enjoy this lab and the report that followed. Researching the homeostasis of living things is quite interesting and the experiment run was easy to execute and got clear results. Daphnias are fascinating little things, aren’t they?
