Does Caffeine Affect the Heart Rate of Daphnia?

Researched by Melissa B.
2000-01




PURPOSE 

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.


HYPOTHESIS

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.

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EXPERIMENT DESIGN

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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MATERIALS
 
QUANTITY
ITEM DESCRIPTION
1 Video camera
1 microscope
30 Daphnia
200mg Caffeine
1500mL distilled water
3 eye droppers
6 Petri dishes
4 Plastic cups

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PROCEDURES

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

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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. 

See the table and graph.

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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. 

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RESEARCH REPORT

INTRODUCTION

Human health is very important for our survival. Caffeine is popular in our society, but yet it is not part of a healthy diet. Large amounts of caffeine can cause serious health related problems. It is possible to use daphnia to test different amounts of caffeine to see how much challenges human health. 

Caffeine

Caffeine is a type of stimulant that speeds your body up and can affect the nervous system, and other parts of the body. This stimulant belongs to the xanthines group. Caffeine dissolves in water and alcohol. It can cause serious health related problems like heart problems, digestive problems, various different kinds of cancer, and birth defects. 
The average adult should have no more than 300 mg per day. 
Caffeine can be found naturally in some plants, but it can also be made by humans in a laboratory, or factory. Caffeine can be found in many popular foods like coffee, tea, cocoa, soda, and chocolate. Caffeine can become addictive if taken in large amounts. Caffeine tastes bitter, and has no smell. It only occurs naturally in small amounts. 
Caffeine has tiny crystals on it that look like needles. Caffeine was produced from plants in the pure form in 1820.
Caffeine is used in prescriptions for some disorders to increase circulation. When taken in large amounts it can cause loss of sleep and headache. 

Daphnia

Daphnia, a kind of crustacean,  is an invertebrate, has no bones in its body, and has a hard shell protecting all of its body except its head. It has three main parts to its body, the head, the thorax, and abdomen.  There are 42,000 kinds of crustaceans. The daphnia is commonly known as the water flea. Other kinds of common crustaceans are the brine shrimp, crabs, and lobsters. 
 Daphnia can be found in ponds, lakes, and calm streams where the temperature is between 21-24°C (68-71°F). 
 Daphnia eat almost any kind of green algae, vegetation, and bacillus coli. The average size of a daphnia is about .2 millimeters. 
  In theory one daphnia can result in up to 13 billion related offspring within 60 days. They lay thick-shelled eggs in the winter, and thin shelled eggs in the summer. In warmer temperatures the eggs will hatch female, and in colder temperatures the eggs will hatch as male. Daphnia are preyed on by fish, tadpoles, and salamanders. 
 Daphnia do not like strong currents, or metal. Daphnia got the name water flea because if its jerky movements. 
 The body of a daphnia is transparent (clear). The average daphnia heartbeat is 300 times a minute. 

Summary

Daphnia is a crustacean that lives in lakes, calm streams, and ponds.
They reproduce rapidly. The average heartbeat of a daphnia is 300 times a minute. 
Caffeine is a stimulant that can speed up the body. If overdosed on caffeine it can cause serious health problems such as: various kinds of cancer, birth defect, heart and digestive problems. Caffeine is found in many popular foods such as: coffee, cocoa, tea, and chocolate. Caffeine can be found naturally in some plants, but can also be made by humans in factories and labs.

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BIBLIOGRAPHY

"Caffeine" Mayo clinic family health resource, 1996 page 274

"Caffeine"[online]http://search.britannica.com

"Caffeine"[online] http://search.onhealth.webmd.com

"Caffeine" World Book Encyclopedia, 2000. Page 200-201

"Daphnia" Science and Math Encyclopedia, 2000

Orlans, Barbra F., Animal care from protozoa  to small mammals, Philippines, Addison-Wesly publishing company,1997 pages 95-100

Perry, Robert, Focus on Nicotine and caffeine Fredrick, Maryland, 21st Century Books, 1990. Pp9-61

 "Stimulant" Comptonís New Media1995

"Water flea" Academic American Encyclopedia ,1998 vol.20, page 40
 

ACKNOWLEDGEMENTS

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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