Experiment Report for: ‘the affect of Caffeine on Daphnia’s heartbeat’ Introduction: Aim: The aim of this experiment is to understand the affect of the drug Caffeine on the rate of a Daphnia’s heartbeat. This is to understand the affect of caffeine on a human’s heart rate and the use of daphnia keeps the experiment fair and safe. Background Research: Daphnia – Daphnia (water fleas) are grouped as crustaceans under the arthropod group of Kingdom Anamalia.
They have an open circulatory system where fluid (there is no distinction between blood and nutritional fluid) in the hemocoel delivers oxygen and nutrients to the organs/ cells directly meaning caffeine enters their system much faster than it would in humans.
This type of circulatory system relies on diffusion and it being fast which is why the majority of organisms with open circulatory systems are small. They have transparent bodies which make them ideal for this experiment so the heart can be observed easily under the microscope.
They are very particular about the habitat they live in and whether they flourish in an area can be brought down to levels of: salinity, dissolved substances, oxygen, pH and ammonia and temperature. [pic] Caffeine – Caffeine is known as a psychoactive stimulant drug and it is the most widely used stimulant. On average 90% of adults consume it on a daily basis. The drug has an effect on mood swings, the cerebal vascular system, also can have a profound effect on the body’s stamina and processes through digestion including colonic activity. It seems that people are not sure it caffeine is n addictive substance as it can be consumed for what people call purpose or pleasure. Some past research has shown that it is has a diuretic effect on the body especially if it hasn’t built a resistance to the drug. Caffeine takes about 45 minutes to be absorbed into the bloodstream. Once the caffeine has reached the heart it attaches itself to specific receptors causing the heart rate to increase. It increases due to increased levels of ATP which affect contractions and relaxations of the heart. These increased levels cause the heart to beat faster.
Hypothesis and Null Hypothesis: Hypothesis- I hypothesize that if I put a daphnia into a caffeine solution then the caffeine will cause an increase in the daphnia’s heartbeat. I hypothesize that different concentrations of caffeine shouldn’t have a different effect on the daphnia’s heartbeat. Variables of the experiment: Independent- The independant variable of the investigation was the the concentration of caffeine solution given to the Daphnia (%) Dependant- The dependant variable is the heartrate of the daphnia (beats per minutes)
Control (independant) variables: • The volume of water given to daphnia under the microscope • The size of the daphnia • The same species of daphnia And there were more that were hard to control e. g the age of the daphnia as this was unknown. Hazards and Ethical Issues: |Hazard/Ethical Issue: |Problem it could cause: |How it can be solved: | |The glassware could have smashed and now be |There could be a cut or injury if it is |Use a dustpan or brush to clear it away. | |on the floor. cleared away by hand. | | |The heat from the microscope evaporates the |The daphnia could die without enough water. |Give the daphnia enough water to survive and| |water around daphnia. | |enough to n ot be evaporated. Also do not | | | |keep wter under microscope too long. | |The daphnia could die due to too much |The daphnia would die due to a heart attack. Use a different daphnia for each caffeine | |exposure to caffeine. | |concentration. Once finished with the | | | |daphnia put it in to the seperate tank of | | | |pond water so it is not reused. | |By ingesting bacterium or viruses from the |The person that ingested the bacteria could |Wash hands after investigation to remove | |pond water. contract an infection. |bacteria from hands that touch the mouth | | | |regularly. | |If handled roughly the daphnia could get |The heart rate would be affected by the |Handle it carefully e. g use a pipette not | |injured. |injury which could affect the results of the |fingers which could squash the daphnia. | | |experiment. | | |The daphnia could get caught in the pipette. |It ould cause stress to the daphnia which |Use a pipette that has been adjusted so it | | |could raise its heart rate and affect the |has a large hole that the daphnia would not | | |results of the experiment. |get stuck in. | All these ethical issues that have been corrected mean that although the experiment is safe (as in not testing humans until the concentrations are perfect to reduce endangering human life) it also keeps the well being of the daphnia in mind. Equipment List: • daphnia (and daphnia tank) Tank of fresh pond water • Microscope • Cavity slides • 1ml pipette • 1ml syringe • 10ml beaker • Stop clock • Pond water & caffeine solution (0. 25% and 0. 5% caffeine) • Board marker to dot on table Method: • Take daphnia from tank in pipette that has end cut off and place in beaker, leave to rest. • Collect microscope and cavity slides, set microscope to lowest magnification. • Collect caffeine solution , pond water and a syringe. Take a beaker of the solution to be used first (start with 0. 25%). • Place one daphnia onto a cavity slide and place under microscope.
Allow the daphnia to adjust for a minute or two. • Using the stop clock and board marker, count the daphnia’s resting heartbeat in 15 seconds by drawing dot on the table for every beat (repeat this to get an average). To calculate what it is in a minute do beats per 15 seconds x4. • Take the daphnia from under the microscope and add some 0. 1% caffeine solution to it. • Place back under the microscope and allow the daphnia to adjust again. • Using the stop clock and board marker, count the daphnia’s heartbeat in 15 seconds by drawing dot on the table for every beat (repeat this to get an average).
Calculate for 1 minute again. • Once finished with that daphnia place into the tank of fresh pond water where it can be left to rest from the effects of the caffeine. • Repeat this process with a different concentration of caffeine solution and use a different daphnia each time. Table of results and Graph: [pic] [pic] Discussion: The more concentrated caffeine solution given to the daphnia, the higher their heart rate became, for example the 0% caffeine solution gave a heart rate of 249 bpm and the 0. 5% solution gave 328 bpm showing an increase.
On the graph there was a positive correlation in favour of the independent variable. These result occurred due to caffeine being a stimulant drug that increases the heart rate. It increases the heart rate by attaching itself to receptors in heart tissue and increasing ATP (energy) levels which control contractions and relaxations of the heart and in turn increase the number of times the heart beats a minute. This is what happened to the daphnia under the microscope the drug caused their heart rate to increase and the different concentrations caused the heart rate to increase at different levels.
In conclusion the null hypothesis was disapproved as the lower concentration of caffeine produced a lower rise in heart rate than the 0. 5% solution did. 0. 25% gave an increase 13 bpm and 0. 5% gave an increase of 79 bpm. Evaluation: This experiment was not very reliable as the when compared with other groups’ the results differed. One anomalous set of results was the row in 0. 5% (181,216,194- much lower than the rest of result here)part of the table that is highlighted in bold where there is random error most likely caused by a counting error by that particular group.
There were not many anomalies as such due to the fact that many variables affect the daphnia itself that could give it a faster or slower heartbeat: • The amount of stress the daphnia was under • The reactions times of the person counting the heartbeat • The age of the daphnia • The gender of the daphnia There are many other factors that could affect this. To improve the reliability of this experiment only use the same gender of daphnia to rule out any gender-related issues that affect heart rate.
Another way to improve reliability is maybe to tape the daphnia whilst they are under the microscope project it onto a large screen and slow down the film that way the person counting could easily take down the number of beats a minute. One other way is to give the daphnia more time to adjust to their situation to try to relieve their stress levels. This also affected the validity as there could have been more than one variable working on the daphnia but in this experiment there was only one variable that was being changed: the concentration of caffeine solution.
The fact that this experiment tried to stop all the other variables from affecting it, it makes it a fair test and therefore valid. This experiment was not accurate because the results were not close to the true value that was found online and in books after the experiment was carried out.
References: Figure 1- http://www. caudata. org/daphnia Figure 2- http://www. evolution. unibas. ch/ebert/publications/parasitismdaphnia/img/full/ch2f5. jpg 1&2- http://www. medicinet. com/caffeine/article. htm ———————– Figure 2 Figure 1- H- Heart B- Brain CE- Compound eye
Cite this Daphnia Heart Rate Experiment
Daphnia Heart Rate Experiment. (2017, Jan 22). Retrieved from https://graduateway.com/daphnia-heart-rate-experiment/