Lab Report Daphnia
Effects of Alcohol, Caffeine, and Temperature on the Heart Rate of Daphnia magna Joseph Ezra Gallo BY124L MW 8:30-11:30 Introduction Ectothermic animals are animals whose body temperature is affected by their surroundings. This means that if the environment is cold the animal will be cold. If the environment is warm the animal will be warm. This is because the animal doesn’t have the capability of regulating its body systems to keep a constant body temperature. When an ectothermic animal is cold, its heart rate will lower.
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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) 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) After an intoxicating exposure to alcohol, an organisms system will be impaired for an extended period of time. 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. Background Daphnia magna is a freshwater ectothermic 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 ectothermic animal. Hypothesis Hypothesis 1: The hypothesis is that lowering the temperature of the surroundings of the ectothermic Daphnia magna will cause its heart rate to lower, and raising the temperature will increase heart rate. Hypothesis 2: The hypothesis is that the heart rate of Daphnia magna will decrease as higher concentrations of alcohol solution are introduced to the system. Hypothesis 3: 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 For the sake of time, the experiment was split into two parts and each part was performed by a different team. One team worked on the effects of temperature changes on heart rate. The other team worked on the effects of Alcohol and Caffeine on the heart rate. Both teams obtained a plastic pipette and cut off the tip at the first graduation from the bottom to allow Daphnia magna to fit into the pipette. The teams each obtained a depression slide and smeared a small amount of petroleum jelly on one of the wells.
Any excess petroleum jelly was wiped off so that there was only one layer on the well. Then each team used their pipette to draw a Daphnia magna from the jar and placed it on the petroleum jelly covered well. A Kimwipe was used to draw off excess fluid from the slide. Then one drop of solution was placed on the Daphnia magna to prevent it from drying out. Each slide was placed on a dissection microscope and the heart was located using the Helms manual and help from the lab instructor. Then one minute was given for the Daphnia magna to calm down.
The following was the procedure used by the temperature team. After the Daphnia was given time to calm down, the team took a reading of its heart rate at room temperature (27 degrees C). The reading was taken by counting the heart beats for ten seconds and then multiplying by six to yield beats per minute. Next, a glass Petri dish was filled with ice water at five degrees Celsius. The cold water Petri dish was placed on the stage of the microscope, and the Daphnia was placed on top of the dish. When the Daphnia had been given a minute to acclimate to the changes, another heart rate reading was taken.
Then the same procedure using the Petri dish to changed environmental conditions was used with cold tap water (23 degrees), warm tap water (30 degrees), and hot tap water (45 degrees). A heart rate reading was taken for each temperature. The following was the procedure used by the team that introduced chemicals into the environment of the Daphnia. First a zero reading was taken before any chemicals were introduced. The zero reading was an observation of the Daphnia’s heart rate before any substances were administered. All fluids were drawn off the slide using the corner of a Kimwipe.
Then two drops of two percent alcohol solution were dropped onto the Daphnia. After a minute a heart rate reading was taken. The same procedure, including using the Kimwipe to draw off previous solution, was then used with four, six, eight, and ten percent solutions. A heart rate reading was taken after each solution was introduced. After the last alcohol solution a Kimwipe was used to draw off all of the solution and a drop of Daphnia culture fluid was added. After a minute another zero reading was taken. The team then used the same procedure used with alcohol to introduce caffeine solution of the same concentrations.
Heart rate readings were taken after each solution. Results Table #1: Effect of Temperature Variations on Heart Rate of Daphnia magna |Temperature (C) |Heart rate (beats/minute) | |Room Temp. |224 | |5 degrees |146 | |23 degrees |182 | |30 degrees |214 | |45 degrees |0 (dead) |
As the environment got further away from room temperature the effects were more pronounced. The heart rate got increasingly lower as Daphnia was placed in colder environments. The heart rate was 224 bpm at room temperature, then 182 at 23 degrees, and then 146 at 5 degrees. When the temperature was considerably higher than room temperature the Daphnia could not handle the extreme, and it died. Death occurred at 45 degrees. (Table 1)
Table #2: Effect of Alcohol Solutions on Heart Rate of Daphnia magna |Concentration of Solution |Heart rate (beats/minute) | |0% |126 | |2% |84 | |4% |57 | |6% |42 | |8% |30 | |10% |18 | As higher concentrations of alcohol were introduced, the heart rate of Daphnia lowered on a steady trend. Heart rate was 84 bpm with 2% alcohol, 57 bpm with 4% alcohol, and 42 bpm at 6% alcohol. It can also be observed that the resting heart rate of this Daphnia was considerable lower than that of the Daphnia used in the temperature experiments. (Table 2) Table #3: Effect of Caffeine Solution on Heart Rate of Daphnia magna |Concentration of Solution |Heart rate (beats/minute) | |0% |6 | |2% |6 |4% |6 | |6% |6 | |8% |6 | |10% |0 (dead) | The zero heart rate was lower than the heart rate at the highest level of alcohol concentration. As higher concentrations of caffeine solution were introduced, there was no effect on this Daphnia. When a ten percent solution was added the heart stopped. (Table 3) Discussion Table 1 showed the trend of Daphnia magna’s heart rate lowering as temperatures were lowered.
Based on this data it can be reasoned that Daphnia’s heart rate will lower anytime it is introduced to a colder environment. At some point Daphnia would freeze and die, but barring that point the heart rate would get lower and lower with colder temperatures. Along the same line of thinking, increasing environmental temperatures would increase Daphnia’s heart rate until the temperature is too high for survival. This data did not completely support the hypothesis because there was no provision for the possibility of death in the hypothesis. If the data had supported the hypothesis the Daphnia would have had a higher heart rate at 45 degrees rather than dying. 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 no trend. As a result of the lack of a trend, this data did not 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 Kimwipe 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 Daphnia in the temperature experiments had a considerably higher heart rate than that of the Daphnia used in the solution experiments. This could show that the solution Daphnia was weak at the onset of the experiment. As a result the alcohol exposure was unrecoverable for that Daphnia. The ectothermic qualities of Daphnia explained the effects of temperature on the animal. (Campbell, 2005) Daphnia was more tolerant to lower temperatures than to higher temperatures. This was expected since Daphnia usually lives in cold water. (LaFave, 2003b) The alcohol affected Daphnia as expected. (LaFave, 2003) When the caffeine was introduced to the system, there was no change. This was not what we expected 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 a standard temperature is most preferred by an ectothermic creature. It also shows 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. Conclusions 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. 4. The ectothermic nature and transparency of Daphnia magna made it very easy to observe the effects of environmental changes. Bibliography 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. http://www. geocities. com/nck12nlafave/daphnia. htm. 2003.