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Daphnia Heart rate-caffeine

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´╗┐Hypothesis: If the concentration of caffeine is increased, the daphnia?s heart rate will increase. I based this on the fact that caffeine increases the number of stimulatory neurotransmitters that are released which increases blood pressure. Method: To measure the heart rate of the daphnia I will first use a pipette to collect some daphnia from the water and place them into a dimple tray and then to a dimple slide and put a cover slide on top to stop the water evaporating too quickly. Then place the slide under a microscope and focus on the heart, being careful not to put the light too close to stop the daphnia drying out. ...read more.


The independent variable is the amount of caffeine drops. This also needs to be controlled carefully to make the results fair. When carrying out this experiment you should be careful not to break any of the glass slides or the microscope and do not let it get too hot. You should also take into consideration ethical issues, for example return the daphnia back to the beaker of water straight after examination because although they do not appear to suffer in the same way as humans, they are still living things. Drops Averages more 210 231 250 230 3 240 240 2 313 216 264 1 153 156 177 died 450 204 died Died 147 0 125 127 110 108 160 156 159 ...read more.


However, there could have been some sources of error. For example the size of each daphnia may have been different or the caffeine solution may have been contaminated. These may have been some of the reasons for the anomalous results. If I did this experiment again I would use a more accurate way to count the heart rate of the daphnia, do more trials to make the results a lot more reliable and have a wider range of caffeine concentration levels to test. Summary: The purpose of this experiment was to investigate how the heart rate of the daphnia changed with increasing caffeine levels. I found that increasing the amount of caffeine, increased the heart rate of the daphnia and from this can conclude that caffeine does increase heart rate, but only until a certain point. ...read more.

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