The Effect of Caffeine on the Heart Rate of Daphnia

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As the caffeine concentration rises, so does the mean heart rate of daphnia.

Risk Assessment:
In this experiment there are the following risks both for the human that carries out the experiment and the daphnia: ← The human that carries out the experiment should be cautious not to touch the lamp with wet hands since it uses electricity. ← Also, be careful not to spill any of the pond water on the floor. ← As for the daphnia, there is a chance for them to die as when they are exposed to light, they are also exposed to heat in which they aren’t used to. ← Moreover, when they are given caffeine of a high concentration their heart may beat so fast that will cause their death. ← Furthermore, there is the risk of the daphnia to dry up, which may kill it in the middle of the experiment.

These are the steps that we followed when doing the experiment: 1. Use a pipette to transfer the daphnia to a cavity slide containing pond water of known volume. 2. Add some cotton fibres to the cavity slide and move them with a fine paint brush in such a way that the daphnia can’t move. 3. Use a calculator to calculate the heart rate. Set its reading to zero and add 1 to the answer. 4. One student will use a stopwatch to count 30 seconds which is the time during which the measurement of the heart rate will take place. 5. Turn the microscope lamp on and locate the heart of the daphnia through the microscope. 6. Measure the beat rate.

7. Repeat steps 1-6 about 4 or 5 times and get an average. Then calculate the heart beats per minute (just by doubling the average). 8. Clean the cavity slide using a tissue and make sure there is no pond water left. 9. Use a pipette to transfer a known volume of caffeine solution of concentration 0.125% to the cavity slide. 10. Transfer the daphnia to the cavity slide using the pipette. 11. Measure the heart beats of daphnia per 30 seconds, following the same procedure as...
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