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Researched by Melissa B.
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The purpose of this experiment was to determine how caffeine affected the heart rate of daphnia Pullex (Water Flea).
I became interested in this idea when I read two different sources that gave me conflicting information about caffeine affecting the heart rate so I wanted to test it.
The information gained from this experiment may be used by the medical world to show what caffeine does to the heart rate and to human health. This information may also be used by patients with serious heart problems, and also by heavy coffee drinkers.
My hypothesis was that as the caffeine increases, so would
the daphnia heart beat.
I base my hypothesis on information collected from the Internet site "Healthcentral.com"that says "that caffeine taken in the faster the heart rate.
The constants in this study were:
-The same species of daphnia
-The same water temperature
-The same microscope
-The same kind of habitat
-The same amount of food
The manipulated variable was the amount of caffeine
used in the water.
The responding variable was the rate of the heart beat.
To determine the heart rate the beats were counted in pulses.
To measure the responding variable a microscope and video camera were used to record how many beats of the daphnia heart rate occurred in 10 seconds. These pulses were recorded with a video microscope and slowed down to accurately count the beats.
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| 1 | Video camera |
| 1 | microscope |
| 30 | Daphnia |
| 200mg | Caffeine |
| 1500mL | distilled water |
| 3 | eye droppers |
| 6 | Petri dishes |
| 4 | Plastic cups |
1. Gather materials
2. Set up video camera to microscope
3. Mix 200mg of caffeine with 500mL of distilled
water
4. Label plastic cup 200mg/L ? 500mL
5. Mix 80mg of caffeine with 500mL of distilled water
6. Label plastic cup 80mg/L ? 500mL
7. Mix 18mg of caffeine with 500mL of distilled water
8. Label plastic cup 18mg/L ? 500mL
9. On the first petri dish around the outside edge write
the numbers 1-5 about 2inches apart.
10. On the second petri dish write the numbers 6-10
11. On the third petri dish write the numbers 11-15
12. On the fourth petri dish write the numbers
16-20
13. On the fifth petri dish write the numbers 21-25
14. On the sixth petri dish write the numbers 26-30
15. On the first petri dish in front of each number place
one daphnia
16. Place petri dish under the microscope
17. Record daphnia on video camera for 12 seconds
18. After 12 seconds turn off microscope light and record
for 3 seconds
19. After 3 seconds turn on light
20. Focus in on daphnia #2
21. Repeat steps 17-19 with daphnia 2-5
22. After recording daphnia 1-5 put one drop of 18mg
caffeine on each daphnia
23. Wait 10 minutes
24. After 10 minutes repeat steps 17-19 with daphnia
1-5
25. Repeat steps 17-19 with daphnia 6-10
26. Repeat steps 22-24 with 80mg/L ? 500mL caffeine mix
27. Repeat steps 17-19 with daphnia 6-10
28. Repeat steps 17-19 with daphnia 11-15
29. Repeat steps 22-24 with daphnia 11-15 with 200mg/L
? 500mL
30. Wait 10 minutes
31. Repeat steps 17-19 with daphnia 11-15
32. Repeat all steps with daphnia 16-30
RESULTS
The original purpose of this experiment was to determine
how caffeine affected the heart rate of daphnia (Water Flea).
The results of the experiment were that in the
first trial the more caffeine put into the water the higher the heart rate.
In the first trial the lowest amount of heartbeats per minute was 360 beats
per minute. The highest amount of heartbeats per minute was 486 times per
minute. In the second trial the lowest amount of heartbeats in a minute
was 366 times per minute. The highest amount of heartbeats in a minute
was 444 times per minute.
CONCLUSION
My hypothesis was that as the caffeine increases, so would the daphnia heart beat.
The results indicate that this hypothesis should be accepted because the more caffeine placed into the water the higher the heart rate.
Because of the results of this experiment, I wonder if temperature make a difference in the caffeine- water mix placed on the daphnia to raise the heart rate. I also wonder if alcohol, a depressant, would lower their heart rate.
If I were to conduct this project again I would have a more accurate way to measure the heartbeats, a larger sample size, and more trials. I would also have a wider range of caffeine levels to test.
I would like to thank the following people for their help
with my science project:
- My father who helped me time the second trial of my project.
- Mr. Sweeney, director of King County Environmental Labs in Seattle who donated the Daphnia pulex for my experiment.
- Mrs. Paskvale who helped me time the first trial of my experiment.
- My mother who bought some of the supplies for my project.
- Mr. NewKirk for staying after school so I could work on my display board.
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Mr.Gunner's 2000-2001 Science Projects