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Daphnia write up

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Does Caffeine affect Heart Rate in Daphnia? Aim: To investigate the effect of caffeine on the heart rate of Daphnia (water fleas). Daphnia are small water fleas between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers. Introduction: What is Caffeine? Pure caffeine is a plant-based alkaloid found naturally in sources such as coffee beans, tea, kola nuts and guarana. Plants create caffeine as a pesticide, to paralyze and kill the insects feeding on them from the effects of over-stimulation. Although a pure chemical caffeine is bitter, nowadays it is also used as a flavour enhancer in a wide range of soft drinks such as coke and energy drinks such as red bull. Caffeine is considered a psychoactive drug. However, it has not been designated a controlled substance, so its use in teas, coffees and sodas is not illegal. It is known to have a stimulatory affect on levels of respiration and heart rate, in addition to being a mild diuretic. Being a stimulant, caffeine causes increased amounts or stimulatory neurotransmitters to be released in the brain. ...read more.


Safety risks One safety risk was the use of glass as it can be very dangerous if it smashed as it is sharp and cannot be seen easily if you are not aware it is there. Some precautions that can be taken are gloves and careful handling. Fair test To ensure it was a fair test i tried to pick daphnia that were around the same size although it was difficult to be accurate. Also i made sure that it was the same person counting the heart rate because some people might be quicker than others. In addition to this I made sure that I started counting as soon as the daphnia was on the microscope so that the heat from the microscope light didn't affect the daphnia. I also made sure that the transfer time from beaker to microscope was always kept roughly the same so the affects of caffeine wouldn't wear off. This helped to make sure that my results would be as reliable as possible. Table of Results: The results gained from the experiment are displayed in the table below: A table showing the heart rate of Daphnia when place in different concentrations of caffeine solution Heart Rate (Beats per Minute) Caffeine % Test 1 Test 2 Test 3 Mean Average 0 170 184 186 180 0.1 204 194 194 197.3 0.2 144 188 182 171.3 0.3 228 230 250 236 0.5 204 194 206 ...read more.


Also if you lose count then you have to start again and this is very time consuming and difficult to do as we only had a limited amount of time. To reduce this risk, we could have used a more powerful microscope. However, I believe that this source of error is one of the most likely reasons for anomalies. Conclusion In conclusion, my results were fairly mixed in comparison to my hypothesis. I believe that if the factors above could have been reduced or eliminated, my results would have followed my predictions. If I were to carry out this experiment again, I would use a stronger microscope in order to increase the accuracy when counting the heart rate (BPM). In addition to this, I would make sure that all Daphnia used were roughly the same size, as this could have also affected the precision of my results. To increase the validity of the finding of this experiment, some further tests would need to be carried out. This would involve repeating the test experiment at each concentration at least 5 times. I would also use more concentration of caffeine solution in order to identify a more specific trend in the results. On the whole I believe the experiment was a success as a trend in the results was identified. Nevertheless if more controls were in place, the reliability and accuracy of the results would have been much improved. ?? ?? ?? ?? Ross Goodman-Brown ...read more.

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