Effect of Caffeine on Daphnia Heart Rate

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Effect of Caffeine on Daphnia Heart rate 24/09/2012 Core Biology Practical (1) Introduction: Caffeine is the drug taken most globally, and can cause health problems such as raised blood pressure. Since we are looking at the heart, we decided to test the effects exposing daphnia to caffeine would have on the daphnia’s heart. Daphnia’s are small water-fleas with transparent body therefore the heart can be visibly seen even without a microscope making the experiment easy to be carried out. Aim: In this investigation, I aim to determine the effect of caffeine on daphnia heart rate Hypothesis: An exposure to higher concentrations of caffeine will cause a distinct increase in the heart rate of daphnia. Null Hypothesis: An exposure to higher concentrations of caffeine will have no effect on the heart rate of daphnia. Apparatus: • Microscope • Stop clock • Cavity Slide • Dropping Pipette • Daphnia in Pond water • Distilled Water • Different concentration of Caffeine Independent and Dependant/Other Variables to be controlled: The independent variable in our experiment was the different caffeine concentration that we will change. The dependant variable will be the heart rate of daphnia. There will be some variables that we need to control in the experiment such as the temperature of the surrounding and water, the volume of solution dropped on daphnia, the size of daphnia and stress of daphnia also the time of acclimatisation must be the same. Method: In our experiment we removed one daphnia from pond water and placed on cavity slide and under a microscope. There was small amount of water on the slide, and a miniscule amount of cotton wool so we could restrict the movement while keeping the daphnia alive. Leave the daphnia for 5 minutes to acclimatise and we then located the heart, and counted the heart beats for 30 seconds, doubling it when done for

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