The Effect of Caffeine on Heart Rate The aim of this experiment was to test the effect of caffeine on the heart rate of a Daphinia (water ﬂeas). Hypothesis: I prediction for this experiment is that an increase in caffeine on Daphinia will increase the heart rate because caffeine is a stimulant drug that increases the activity of the nervous system. Equipment; The equipment that I will use for this experiment is as follows: * Culture of Daphnia * Cavity slides and cover slips * Dropping pipettes * Distilled water * Caffeine tablets * Cotton wool * Standard glassware (beakers, measuring cylinders) * Stop watch * Paper towels * Light microscope Method; The procedure I will use is as follows: * Place afew strand of cotton wool on a cavity slide to help
restrict movement of Daphnia. Transfer a water ﬂea to the slide using a large pipette. Remove the water surrounding it using ﬁlter paper and add a few drops of distilled water. Use as much water as possible to allow the water ﬂea to maintain sufﬁcient supplies of oxygen. View the ﬂea under a medium power and focus on the heart which can be seen through its translucent body. * Use a stop watch to record the number of heart beats in a minute. Tap a pencil on a piece of paper for each beat and count all the marks at the end of the minute. Record the results in an appropriate table. * Repeat the procedure using several different concentrations of caffeine. Results; Concentration Test 1 Test 2 Test 3 Test 4 Test 5 Average 0 100 100 100 100
100 100 x10 -5 61 95 110 108 120 99 x10-4 70 100 84 115 85 91 x10-3 81 104 123
102 Graph; [IMAGE] Conclusion and Evaluation: My results appear fairly unreliable as know obvious pattern occurs. They do not support my prediction but I believe there are several reason why this may have happen. There was no obvious increase in heart rate from the control (where the concentration of caffeine = 0), in fact in some cases there was even a decrease. I did not expect this because...