Water temperature will be controlled to maintain the fairness of the experiment; this means it will be kept at room temperature as best as possible. That will include turning off the microscope so that the illuminator does not heat up the water, this also ties in with the method I will be using which is to count the first 10 seconds of the daphnia’s heart beat then times it by six.
The same microscope will be used so that the distance from the illuminator is the same to keep variables controlled.
The same species of daphnia will be used; different species could alter the results because they might have different anatomies and resistances.
Distilled water will be used instead of tap Water, this is because of the chemicals in tap water which can cause shock to aquatic life, and as well the distilled water will be at room temperature.
The daphnia could range in different size, on average the same size will be tried and tested when possible.
Apparatus & Materials;
Standard Microscope
Daphnia magna culture
Distilled water
Caffeine
Test Tubes
Test Tube Rack
Pipette
Depression Microscopic Slides x 20
Cotton Wool
Test tubes will be used to mix the distilled water and caffeine solution together; I have chosen to use test tubes instead of conical flasks or beakers because they are compact and more suitable for this type of experiment.
Distilled water in a frosted bottle so that sun light can’t affect the temperature and will help to keep the experiment fair instead of leaving it out in the open.
A microscope will be used so that the heart beat can be counted and microscope slides that a daphnia can be placed on.
Pipettes will be used throughout the experiment, 1 pipette for each solution made, 1 pipette to extract the daphnia and place onto the slide,
1 pipette to extract some solution so that the daphnia can’t move around.
The Caffeine Solution is a dark colour solution and will be used sparingly.
Safety & Ethical Issues;
Take care of glassware.
Sanitise experimental area after.
Wear eye protection at all times.
Care when handling chemicals as they may stain.
Dispose of Daphnia properly
The Daphnia being used are for the good-will of science and to gain knowledge, they are used sparingly and if possible will be return to the sample. However there is a possibility that the daphnia can decease and this will be taken into account.
Method;
The control of the experiment is a pure distilled water solution without caffeine that will be used to determine a base for my experiment.
The other solutions will be caffeine that is 100% Distilled water will be called S00, 30% diluted, 20% diluted, 10% diluted.
Below is a chart that has the measurements of each solution that will be used in the test.
A Daphnia will be extracted and placed onto a cavity slide per trial, caffeine will be added to the slide, its heart beat will be counted for 10 seconds then multiplied by 6, this will be carried out 5 times per solution and each trial will start with a daphnia that has not been affected by the caffeine already. Results:
From the results, the Control has an average of 192.2 beats per minute, This will be used as the standard heart beat of a Daphnia. The standard deviation indicates that the results are accurate with around 25 beats per minute in variation. The linear trend line for the S00 solution is weakly positive, from this it is clear that the results seem to be precise and accurate in this trial.
The 30% Diluted solution gave an average of 256.2 beats per minute, this is a 64 BPM increase from the 100% Distilled water solution.
The 20% Diluted solution had an average of 301.2 BPM which is an increase of around 55Bpm from the S30 solution and a 109Bpm increase from the S00 Solution. The solution is not fully caffeine yet and the BPM has risen significantly enough to give an early indication that the hypothesis is correct. The Linear trend line is weakly negative, almost neutral and the standard deviation is 13.97 which means’ that the data collected was roughly 14Bpm away from the average in each trial.
S10 has an average of 342.4Bpm which is 41.2Bpm increase then the S20 solution, An 86.2Bpm increase in the S30 Solution and a 150 increase compared to the Distilled water Solution, the trend line is strong positive and the standard deviation is 19.61 which suggest that it is the second most-accurate trials recorded.
These results support the Hypothesis ‘My hypothesis is that a daphnia’s heart will beat faster when it receives a dose of caffeine’. From the results the heart beat of a daphnia has risen significantly in response to the higher dose of caffeine.
Limitations and Variables;
Some variables that I was not able to control was that some of the daphnia had several offspring in the ovary so this could of affected the tolerance of the caffeine making the daphnia more susceptible.
Another problem was that more than 80% of the daphnia had ceased over 3 day period in the tank. This could affect the results S00,S30,S20 Because they were taken when the population was at its highest, however I believe this to be an advantage because the more healthy daphnia were left in the tank.
Another problem was that the illuminator from the microscope increased the heat on the Cavity slide greatly. The microscope had to be turned off whenever not used but, the method I used of counting the heart beats for 10 seconds then multiplying it by 6 was a great advantage because the microscope did not have to be on for longer.
One problem seen with the daphnia is that some had developed a darkening of the shell which had spread differently in daphnia.
According to Scientists this is bacterium Pasteuria ramosa or P. Ramosa. A few weeks are needed for the parasite to product spores. By the time the daphnia is ready to release its offspring is will have already been effected and be on the way to a slow death. The parasite kills from host-to-host, however the parasite has evolved to only kill the host when it has finished producing spores.
(2) (3)
A limitation in the experiment was that only the BPM could be recorded and that the time
In which it takes the caffeine to effect the daphnia throughout, at its peak and after the
Trials have been concluded.
One modification to the experiment could be that different diluted solutions could be tested e.g. 00,50,100 so that the results can be compared and to test if there is a pattern or equation that can be made from it between the distance in solution and amount of heart beats. I would not change the amount of trials carried out per solution, I think they provided stable and precise data for conclusions to be made from.
Conclusion;
Based on the results, they show that caffeine does affect daphnia due to the chemical processes in the body which occur in humans as well. The results prove the hypothesis correct, and the data is accurate, precise and reliable, we can see this with the trend lines and the standard deviation not being over a large area. The graph will all of the results binded into them show a positive increase in the amount of heart beats and the experiment results were recorded without bias to the hypothesis and the outcome which was unknown at the time.
Bibliography
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2 -
3 - http://www.sciencedaily.com/releases/2006/05/060531094912.htm