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Effect of Caffeine on Heart Rate in Daphnia

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'Does Caffeine Affect Heart Rate In Daphnia?' Effect of Caffeine on Heart Rate in Daphnia TITLE 'Does caffeine affect heart rate?' HYPOTHESIS I predict that the water fleas heart rate will increase as caffeine is added. METHOD The Investigation was carried out in the following way: * A few strands of cotton wool were placed on a cavity slide (this helped restrict the movement of the water flea) * One large water flea was put on a cavity slide using a pipette * Water was removed from around the water flea using filter paper * One-Two drops of distilled water was added (This helped maintain sufficient oxygen supply to the flea) * To keep the temperature in control, a cavity slide was placed under the slide to minimise the amount of heat and light going through to the microscope * Water flea was viewed under low power * Focus was paid to its heart which could be seen through its translucent body * Stop watch was used to record the heart beats per minute * The procedure was repeated using different concentrations of caffeine * Results were recorded in a table RESULTS Table of results: [Caffeine] (mg dm ) ...read more.


did not fit in with the trend for this concentration. CONCLUSION According to the results and graph, my hypothesis was proved correct (that the heart rate increased as the caffeine concentration was increased). Although the last point in the graph does not follow this. I think this is mainly due to the fact that there were two anomalous results and this affected the calculation of the mean heart rate. DISCUSSION A daphnia's heart will beat faster when it receives a dose of caffeine. Caffeine belongs to a class of compounds called methylxanthines and can block a receptor on the surface of heart muscle cells for adenosine. In fact, it is caffeine's blockade of the A1 adenosine receptor in the heart that causes the heart to pound after a significant caffeine dose. Caffeine and similar compounds also inhibit a class of enzymes known as cyclic nucleotide phosphodiesterases. These enzymes are, in part responsible for degrading a stimulatory signal produced when excitatory neurotransmitters activate different neurons in the central nervous system (CNS). ...read more.


* The amount of caffeine added on the daphnia will vary even though it was added using a dropping pipette. This could account for the anomalous results at the 7.5 and 10.0 mg dm concentration of caffeine. Limitations: * The whole experiment should be repeated atleast twice to make the results more reliable * A stethoscope could be used for accuracy of results, but this is not safe to use. * If the caffeine was added in smaller doses, i.e. the concentration did not increase so rapidly, e.g. if we increased the concentration by 0.5 mg dm then we could have seen a clearer pattern relating the concentration of caffeine and its effect on heart rate. RISK ASSESSMENT Care had to be taken in the duration of this experiment. This was because the concentration of caffeine could have a big impact on the daphnia. Too much caffeine could kill the daphnia and too much water could fill the daphnia's lungs up and also kill them. These factors had to be taken into consideration when doing the experiment. This experiment was fairly accurate in terms of ethical considerations. The only errors may have come from human errors, which are unavoidable. A Level Biology BIOLOGY SALTERS 1 ...read more.

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