Need a reason to break the addiction?: Increasing caffeine concentrations increases heart rate and increasing nicotine concentrations decreases heart rate of Daphnia magna

Caffeine and nicotine are known to affect cardiac muscle cell receptors, and both chemicals have been studied recently due to the increase in caffeinated drinks and e-cigarettes being sold in the market. This experiment studies whether changing concentrations of caffeine and nicotine solutions affect the percent change in heart rate of the crustacean  Daphnia magnus . We hypothesized that increasing the concentration of nicotine will cause a decrease in percent change in heart rate (giving a larger negative value), and increasing the concentration of caffeine will increase the percent change in heart rate. This study investigates how the concentration of the chemical solutions affect heart rate rather than simply comparing changes between the two. The heart beats of twelve  Daphnia magnus  were counted both before and after being introduced to a solution; the concentration and type of solution were compared by the calculated percent  c hange in heart beats per minute of the  D. magnus.  Since the heart of the  Daphnia  are similar to those of vertebrates, further studies on the effects of caffeine and nicotine on the heart rate and health of humans could be created based on our results .