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The Effect of Alcohol and Caffeine Concentrations on Daphnia Magna


The target of this experiment was to study the effects of alcohol and caffeine on the heart, using the Daphnia Magna as the test subject. The hypothesis was: Increasing the concentration of caffeine in which the Daphnia Magna is submerged will cause its heart rate to increase, while increasing the concentration of alcohol in which it is submerged will cause its heart rate to decrease. To test this hypothesis two Daphnia Magna were exposed to either alcohol or caffeine and its heart rate recorded by placing it on a microscope slide and counting the number of heart beats. It was deducted that the alcohol and caffeine had a very notable effect on the heart, with alcohol slowing it down and caffeine speeding it up. At the highest concentration of alcohol, the heart rate slowed and in turn the higher concentration of caffeine affected the heart rate by increasing it. I feel that the same concept of the effect of alcohol and caffeine on Daphnia Magna would be the same concept for its effect on humans also sense alcohol is a depressant it tends to slow down the body as Caffeine is well known for giving our bodies a boost of energy.

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It was obvious to test the effects that alcohol and caffeine have on the human heart. The effects of alcohol and caffeine were a distinct interest sense they are drugs that are consumed on a large scale in society. However, because it is difficult to perform experiments of this nature on humans and get accurate results, we decided to use Daphnia Magna as a substitute for a human. Though humans and Daphnia Magna are different organisms, alcohol and caffeine should have an almost identical effect on them. The effect when both organisms are exposed to the same amounts of alcohol and caffeine should be more noticeable in Daphnia Magna because they are much smaller, so in turn the chemicals will flow through the Daphnia Magna’s form quicker and effect each cell more.

There are many explanations why Daphnia Magna are commonly used compared to the use of a human as test subject. Firstly, Daphnia Magna are simple organisms compared to humans thus there are less factors that we have no control over what could likely affect the heart rate. Secondly, the heart of the Daphnia Magna is easy to view and examine because of their transparent body form. Thirdly, it is logical to use a Daphnia Magna because the effects of the drug will be observed much more quickly, within moments compared to around half an hour in humans. Also, to get usable results, it would be necessary to supply a human subject with a reasonable large amounts of alcohol or caffeine, which wouldn’t be good for short term health, as well as unscrupulous. The hypothesis under investigation was developed because depressants, like alcohol tend to decrease the activity of the body’s organs, whilst stimulants like caffeine tend to increase such activity.

Methods and Materials

Two Daphnia Magna specimen were collected from the habitat container and then placed each in their own hanging drop slide carefully so they would not slide all over like they would a traditional flat slide. This way one slide would have one Daphnia Magna testing the varying concentrations of alcohol and the other Caffeine.

In caffeine we readied concentrations of 0.25%, 0.05%, 0.75% and 1.0% levels of concentration. One member held a bottle of distilled water to be used in between concentrations. The water allows the Daphnia Magna to rest a moment that way it doesn’t die to quickly from the various concentrations. One member will begin the experiment by tallying its heart beats per seconds to allow for an average heart rate. The group then subtracted the water from the slide and replaced it with the fist concentration of caffeine counting the heart beat 15 seconds again then quickly taking away the caffeine and replacing it back with distilled water. We repeat this process and collect the data until all concentrations have be used and the data compiled.

Alcohol there were 2%, 4%, 6%, 8%, and 10% of concentrations. Using a Microscope as well as a fresh bottle of water to adjust the Daphnia Magna to the stress of the many concentrations makes the experiment a little easier. As we did with the caffeine the group used a fresh Daphnia Magna collected the average heartbeat and began the process of subjecting the Daphnia Magna to the Alcohol concentrations collecting the heart beat data and observing how it changes with each concentration.


Results demonstrates the profound effect the alcohol and caffeine both have on the heart. As shown in figure 1 and 3 the higher the concentration of caffeine the faster the heart becomes. In figures 2 and 4 Alcohol seems to have the opposite affect and slows the heart rate down increasingly with each concentration. Within our results it can be determined that when humans consume alcohol that they will experience a slowness and often a more depressed feeling. On the flip side when humans are exposed to caffeine it can be seen that there is a burst of energy “Caffeine is a central nervous system stimulant. Your central nervous system includes your brain, spinal cord, and the other nerves in your body. Caffeine’s main effect on your body is to make you feel more awake and alert for a while” (FDA, 2007)

Table 1: group data for Caffeine concentrations

Caffeine Concentrations and how they affect the heart rate
Concentration Heart Rate 15 sec Heart Rate (BPM)
0% 53 216
0.25% 42 168
0.50% 39 156
0.75% 28 112
1.0% 31 124

Figure 1: the graph that shows the group average heart rates when exposed to the different concentrations of caffeine provided that the Daphnia Magna heart rate was counted for 15 seconds then calculated to BPM

Table 2: Group data for alcohol concentrations

Alcohol concentrations and how they affect the heart rate
Concentration Heart Rate 15 sec Heart Rate (BPM)
0% 31 133.33
2% 27 108
4% 24 96
6% 12 68
8% 19 76
10% 14 56

Figure 2: the graph that shows the group average heart rates when exposed to the different concentrations of alcohol provided that the Daphnia Magna heart rate was counted for 15 seconds then calculated to BPM.

Table 3: Class data for caffeine concentrations

Water Control AVG 0.25% Caf 0.5% Caf 0.75% Caf 1.0% Caf
KR 216 168 156 112 124
g1 45.3 56 84 96 88
G2 248 448 452 480 508
Jeep 132 208 164 220 188
G5 133.3 120 112 124 136
Average 154.92 200 193.6 206.4 208.8

Figure 3: the graph that shows the class average heart rates when exposed to the different concentrations of caffeine.

Table 4: Class data for Alcohol concentrations

Initials Water Control AVG 2% Alc 4% Alc 6% Alc 8% Alc 10% Alc
KR 133.33 108 96 68 76 56
g1 54 248 285 236 188 172
G2 205.3 312 240 180 64 48
Jeep 181 148 152 124 124 108
G5 205.3 240 196 232 212 100
Average 155.8 211.2 193.8 168 132.8 96.8

Figure 4: the graph that shows the class average heart rates when exposed to the different concentrations of alcohol.


“Alcohol affects every organ in the drinker’s body and can damage a developing fetus. Intoxication can impair brain

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