Does Caffeine affect heart rate?

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Does Caffeine affect heart rate?

Aim: To investigate the effect of caffeine on the heart rate of Daphnia

Introduction:

I will be measuring the heart rate of a Daphnia once I have exposed it to different concentrations of caffeine to see if caffeine affects heart rate.

I have done a preliminary experiment so that I know which concentrations to use, how long to measure the Daphnia's heart rate for and so that I have practised counting the Daphnia's heart beat. This means that I will harm the Daphnia the smallest amount possible, will know how long the experiment will take me and will be fully prepared.

My hypothesis is: when the concentration of caffeine increases, the heart rate of the Daphnia will also increase.

I think this because caffeine is a stimulant of the central nervous system, cardiac muscle, and respiratory system. This means that it increases your body actions, such as heart rate, blood pressure and metabolism. I believe that it will have the same effect on Daphnia so that their heart rate increases as the concentraion of caffeine increases.

Variables:

My independent variable is the concentration of caffeine,