The Effects of Caffeine on the Heart Rate of Daphnia magna

1. The Effects of Caffeine on the Heart Rate of Daphnia magna Laura Haggerty

2. Question How does the introduction of caffeine affect the heart rate of Daphnia magna?

3. Background Information • Daphnia magna are minute water crustaceans commonly known as water fleas. • Their skin is transparent making all internal organs visible under microscope • Typical life span is approximately 40-56 days • Environmental factors and temperature can alter the life span of Daphnia magna. • Caffeine (C8H10N4O2 ) is a stimulant drug • Heart rate is defined as the number of beats per minute

4. Hypothesis It was hypothesized that as Daphnia magna were introduced to increasing concentrations of caffeine, their heart rate would also increase

5. Variables Independent variable- concentration of caffeine Dependent variable- heart rate of Daphnia magna Constants- spring water Control- spring water with no added caffeine

6. Materials Daphnia magna Transfer pipettes 100 mL graduated cylinders (2) 5 petri dishes Compound microscope Depression slides Small container 250 mL beakers (5) Caffeine pill (200 mg) Detain

7. Procedure Serial dilutions were made in five 250 mL beakers This resulted in a control and four varying concentrations of 1 mg/ml, 0.1 mg/ml, 0.01 mg/ml, and .001 mg/ml The Daphnia magna were placed in each solution in small petri dishes before being transferred to depression slides. The depression slides were placed on a compound microscope and observed. The heart rate of the Daphnia magna was then counted for ten seconds and multiplied by six to calculate the results for heart rate per minute. Five trials were performed for each of the four concentrations and the control.

8. Data

9. Heartbeats per minute

11. Analysis • The hypothesis was supported. When introduced to higher concentrations of caffeine, the heart rate of Daphnia magna increased. • The two most concentrated solutions proved to be significant exhibiting the fact that caffeine does affect the heart rate of the Daphnia, but the solution must be concentrated to a certain level in order for a distinct variation in heart rate to occur. • For further research, one might extend the experiment to test other small organisms • Another extension could be to perform additional trials with more concentrations to pinpoint the exact concentration at which toxicity occurs.

12. Conclusion • The introduction of caffeine had a substantive effect on the heart rate of Daphnia magna tested thus supporting the hypothesis that an increase in caffeine concentration would instigate an increase in heart rate. • The more concentrated solutions of .1 mg/ml and higher were shown to have had a significant effect on the heart rate.

13. Works Cited