Every organism??™s full contraction and dilation of the heart is different. The way organism??™s heart rate changes to different chemical solutions and temperature change is very similar. The purpose of this experiment is to study the effect of water, alcohol and caffeine in the heart rate on the Daphnia. According to existing research and scientific literatures, both of these drugs have similar interactions with animal cells but produce opposite effects.
Daphnia magna or water fleas are small aquatic, transparent organism and they belong to the Phylum Arthropod and it the Class Crustacean. The Daphnia magna is a perfect organism for this experiment because Daphnia are small and they can easily be placed under the microscope, their exoskeleton body is transparent, therefore the heart can be easily seen, they are very sensitive to their environment, therefore they will quickly react to the stimuli, they are cold blooded and easy to keep them in the laboratory and handle them throughout the experiment. The scientific question is: How will the Daphnia magna react to several different stimuli Daphnia??™s heart rate won??™t be affected in its natural environment rather be affected by the addition of caffeine. My hypothesis was that as the caffeine increases, so would the Daphnia heart beat.? Also, the heart rate is affected by cold temperature change which will decrease the heart rate. The Daphnia will have to be placed in the distilled water to recover its natural habitat, so that the heart rate will be normal again. Humans and water fleas have a common ancestor and we both belong to the Animal Kingdom. As a result of this it??™s possible that we will react to neurotransmitters and cold temperature change the same way. Ectodermic animals are animals whose body temperature is affected by their surroundings. When an ectodermic animal is cold, its heart rate will lower. When the animal is warmer, the heart rate will raise ??“ as long as the temperature isn??™t sufficiently high to harm the animal. (Campbell, 2005) The concentration of the alcohol and caffeine were our independent variables. The heart-beat rate of Daphnia under different conditions was the dependent variables. The temperature of the room, water used and the pH of water was kept constant, which were our control variable.
Alcohol is a depressant. This means that body systems will slow down when alcohol is introduced. In particular, the heart rate will get consistently lower. If too much alcohol is added, it will result in the death of the animal. The alcohol acts by inhibiting the nervous system. (LaFave, 2003) Caffeine is a stimulant. It will work by causing the nervous system to work faster. Also, it will cause the blood vessels to constrict. (LaFave, 2003) These effects will work together to increase an animals heart rate. Under normal circumstances, the heart rate will increase as more caffeine is added. At some point the high concentration of caffeine will cause the heart to stop functioning.
The effect of one outside substance can impair the effects of other substances. In this experiment we will intoxicate an organism. As a result, the nervous system will have difficulty responding when we introduce a stimulant. The caffeine will have no effect on the organism, because it will be insufficient to overcome the effects of the alcohol exposure. Daphnia magna is a freshwater ectodermic crustacean commonly referred to as a water flea. Its body is transparent. Because of its transparency we can observe the
effects of substances on its body without surgical procedures. We can observe the heart of the Daphnia to be dorsal to the backbone, just behind the head. (Helms, 1998) The
average Daphnia has a heart rate of about 180 beats per minute under normal conditions. We will observe the effects of temperature fluctuations, alcohol, and caffeine on this ectodermic animal.
The hypothesis is that the heart rate of Daphnia magna will decrease as higher concentrations of alcohol solution are introduced to the system.
The hypothesis is that the heart rate of Daphnia magna will increase as higher concentrations of caffeine solution are introduced to the system.
Materials and Methods: The light for the microscope should be OFF as much as possible to avoid overheating the Daphnia. We use a clean pipette to transfer a Daphnia with a drop of liquid onto a slide. Make sure the drop is small so that the Daphnia can??™t swim out of your field of view.
Then, carefully place the slide under the microscope and focus on the Daphnia so that you can see the beating heart. Remember, the heart lies on the back of the Daphnia.
Now, we count the number of heart beats that occur in 15 seconds. My lab partner timed 15 seconds for me, and I counted heartbeats. We had to make our measurements
quickly, so that the Daphnia does not become stressed in the small volume of water.
After, the observation immediately record the number of heart beats in the data table on the next page. Multiply the number by 4 to get the number of beats per minute. Take at least three separate heart rate measurements for each individual Daphnia and calculate
the average of the three measurements. When we finish recording the heart rate in water (the CONTROL solution), add ONEDROP of the 1% ethanol solution to the slide. Turn the light OFF and wait 30 seconds. Turn the light back on and count the number of heart
beats for 15 seconds again, repeating at least 3 times. Multiply each count by 4 to get the heart rate per minute.
Table #1: Effect of Red Bull on Heart Rate of Daphnia magna
|Concentration of solution |Heart rate (beats/minute) |
|2% |186 |
|10% |186 |
The increase to 10% concentration from 2% concentration of red bull did not change the heart beat rate of Daphnia magna. It was 186 bpm on 2% as well as 10% concentration.
Table #2: Effect of Alcohol Solutions on Heart Rate of Daphnia magna
|Concentration of Solution |Heart rate (beats/minute) |
|1% |190 |
|3% |100 |
|5% |60 |
As higher concentrations of alcohol were introduced, the heart rate of Daphnia lowered on a steady trend. Heart rate was 190 bpm with 1% alcohol, 100 bpm with 3% alcohol, and 60 bpm at 5% alcohol.
Table #3: Effect of Caffeine Solution on Heart Rate of Daphnia magna
|Concentration of solution |Heart rate (beats/minute) |
|1% |192 |
|2% | 196 |
As higher concentrations of caffeine were introduced, the heart rate of Daphnia increased. Heart rate was 192 bpm with 1% caffeine, and 196 bpm with 2% caffeine.
Table 1 showed the trend of Daphnia magna??™s heart rate is same. The red bull had no any effects on Daphnia??™s heart rate. Table 2 showed the effects of alcohol on Daphnia??™s heart rate. The higher the concentration of alcohol, the lower Daphnia??™s heart rate got. It can be assumed that this trend would continue until the Daphnia died. This data supported the hypothesis. Table 3 showed the effects of caffeine on Daphnia. This table showed the increase in the concentration of caffeine increased the heart rate.
This supported our hypothesis. Sometimes, the result lacks the trend and doesn??™t support the hypothesis. This can be explained several ways. First, it could have been experimental error. The solution team could have forgotten to use a wipe to remove an alcohol solution from the Daphnia. There also could have been errors in the way Daphnia was handled. Another possible explanation was that the Daphnia was too weak from the beginning. The alcohol affected Daphnia as expected. (LaFave, 2003) When the caffeine was introduced to the system, there was again some change. This was exactly opposite of the alcohol effection. The results were based on knowledge of how stimulants affect animals. (LaFave, 2003) This can be explained by the excessive nervous system inhibition caused by the alcohol.
This experiment can be used to show the practical application of chemicals and temperatures in regulating body function. It showed that chemicals can be introduced if there is any reason to sedate or revive a creature. These things have an obvious practical application in the medical field. Another application is in biological research when samples need to be kept alive, sedated for viewing, or revived.
1. Daphnia magna is influenced by certain environmental conditions.
2. Daphnia magna cannot function in extreme situations.
3. Daphnia magna was unable to recover from the high alcohol concentrations.
Campbell, Neil., Jane B. Reece. 2005. Biology, 7th ed. Beth Wilbur ed. Benjamin
Cummings Publishing, San Francisco, CA. pp 833-834.
Helms, Doris., Carl Helms., Robert Kosinski., John Cummings., 1998. Biology in the
Laboratory, 3rd ed. Judith Wilson ed. W.H. Freeman and Company Publishing,
New York, New York. pp. 38-14 ??“ 38-16
LaFave, N. Virtual Water Flea Experiment.