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Effect of caffiene on the heart rate of Daphia

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´╗┐The effect of caffeine on the heart rate of Daphia. Hypothesis Caffeine mimics some of the effects of adrenaline and noradrenaline and increases the rate of concentration and relaxation of each heartbeat, so I believe the daphia?s heart rate will increase with the gradual increase in caffeine concentration. Therefore I predict a resultant positive correlation. Variables Independent variable is the heart rate of the daphia. This will be controlled by placing a daphia underneath a microscope and counting by the human eye, the number of times its heart beats. Dependant variable is the concentration of caffeine which is given to the daphia. This will be controlled through using the correct equipment e.g. volume beakers and pipettes etc. Controlled variable could be to choose daphia of the same age and size, as the heart rate will differ, for example in younger daphia their heart rate is faster as they are still developing or larger daphia as they have a bigger surface area to be covered so blood has to be pumped quicker. Uncontrollable variables(to an extent) will be the temperature of the daphia?s water as this can affect their heart rate also e.g. ...read more.


It is accepted that caffeine effects humans and daphnia in similar ways, they are still different organisms so will be effected in slightly different ways. Although the general effects- increasing and decreasing heart rate- should be the same, the amount of variation will almost certainly be different, because humans are much larger than daphnia, a much larger quantity of caffeine would be required to produce the same degree of change in the heart rate. To get results that are completely accurate for humans, a large scale medical study would have to be undertaken. When the daphnia is being observed under the microscope it is in close proximity to the lamp, which gives out heat, the little volume of water/concentrated caffeine concealing the daphnia, only requires a small amount of heat to raise the temperature. If the daphnia is under the microscope for just under five minutes, it?s likely to raise the temperature by several degrees, possibly increasing the daphnia?s heart rate. However this limitation can be counterbalanced as all daphia are under the same condition. Apparatus Daphia(water flees) A plastic transfer pipette A watch glass A dissecting microscope Beaker x2(one for used daphia, one for non-experimented daphia) ...read more.


Evaluation Although the hypothesis was proven to be correct, there were some anomalies found in the experiment (circled in the results table). These readings were much lower than the other repeats, this could be due to human error; misreading the heart beat due to the speed of contractions, or the size of the daphia; maybe the daphia used for that certain repeat could cope with the concentration of caffeine more effectively that the others for that certain concentration. Another explanation is that of the room temperature could have been at different temperatures at different times or at different areas in the room, for example near windows or radiators. This could have well affected the daphias heart rate. Equipment was also found to affect the results, to get a true reading of a daphias heart rate, more technical equipment was needed. It was literally impossible to get an accurate reading from the control group of daphia, never mind when the heart rates increased with caffeine. Equipment could be improved by using better microscope lenses and the use of a ?clicker? these pieces of apparatus would aid a better reading as I would of have a clear view of daphias heart rate to reading and a more sustainable way of counting heart contractions for the 20 second period. ...read more.

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