Notebook for October 2nd• Pick up your Folder and staple two lab sheets

together• Reflect yesterday • Write: Today’s Date • Write down Essential Question (Explain the

Essential parts of an experiment)• Thought Question: What factors effect the heart

rate of human beings

The Effects of Caffeine on the Heart Rate of Daphnia magna

Abstract

• Caffeine is a part of our everyday lives, but how does it affect other species? The purpose of this experiment was to test the effect of caffeine on the heart rate of Daphnia magna, small water crustaceans.

• Four serial dilutions of a 1.00mg/ml solution were made and spring water was used as a control. Daphnia magna were then exposed to each of the five solutions and placed on a depression slide. Because their semi-transparent skin allowed for a clear view of the beating heart, the heart rate could be measured with the use of a microscope and stopwatch. After the heart rate was counted for 10 seconds, the data was then multiplied by six to equal the number of beats per minute.

• It was hypothesized that an increase in caffeine concentration would increase the heart rate of the Daphnia. The data collected supported this hypothesis. The data displayed a significant increase in heart rate per minute as the concentration was increased. This demonstrated a direct correlation between the caffeine and the heart rate of the Daphnia. In a practical application one could make the connection that caffeine affects human in a similar manner as it did the Daphnia, in the fact that it has been known to increase their heart rate as well.

Question

• How does the introduction of caffeine affect the heart rate of Daphnia magna?

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

Hypothesis

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

Variables

• Independent variable- concentration of caffeine

• Dependent variable- heart rate of Daphnia magna

• Constants- spring water• Control- spring water with no added caffeine

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

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.

Data

Heartbeats per Minute

Concentrations Trial 1 Trial 2 Trial 3 Trial 4 Trial 5

0.00 mg/ml 180 168 204 210 210.001 mg/ml 192 162 216 222 216.01 mg/ml 210 192 228 238 228.1 mg/ml 204 226 234 240 2401 mg/ml 228 228 234 240 240

Averag e Heartbeats per Minute

0

50

100

150

200

250

300

0 mg/ ml 0.001 mg/ml 0.01 mg/ml 0.1 mg/ml 1 mg/ml

C oncentrations

Heartbeats per m

inute

*P values ≤ .05 are significant

T-test Results (P values)

Control vs .001 mg/ml 0.6

Control vs .01 mg/ml0.08

Control vs .1 mg/ml 0.01

Control vs 1 mg/ml 0.002

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.

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.

Works CitedClare, J., Ph.D. (2002, July). Daphnia: An aquarist’s guide. Retrieved from

http://www.caudata.org//

Corotto, F., Ceballos, D., Lee, A., & Vinson, L. (2010). Making the Most of the Daphnia Heart

Rate Lab: Optimizing the Use of Ethanol, Nicotine & Caffeine. The American Biology

Teacher, 72(3), 176-179. doi:10.1525/.2010.72.3.9

Dowshen, S. (2010, May). Heart and circulatory system. Retrieved from Nemours website:

Dowshen

Gavin, M. (2008, January). Caffeine. Retrieved from Nemours website:

http://kidshealth.org//_alcohol//.html

Miller, K., & Levine, J. (2002). The heart. In Prentice Hall Biology (pp. 26, 944-946, 1064).

Upper Saddle River, New Jersey: Pearson Education.

Olson, A., PhD. (2010). Caffeine and Heart Rate: A Pharmacological Study Using Daphnia

magna. In Science buddies. Retrieved September 16, 2010, from

http://www.sciencebuddies.org/fair-projects/_ideas/

Zoo_p048.shtml?fave=no&isb=c2lkOjEsaWE6Wm9vLHA6MyxyaWQ6NzE2MTY5OQ

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Pohler, H. (2010, January). Caffeine intoxication and addiction. The Journal for Nurse

Practitioners, 6(1), 49-52. Abstract retrieved from http://www.npjournal.org//-

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