Planning:
-Risk Assessment:
1. I need to be aware of weils disease so I will not come in to direct contact with the pond water and regularly wash my hands thoroughly throughout the experiment.
2. I will need to constantly keep my glassware on throughout the experiment to prevent any substances getting into my eyes
3. I will be using a microscope to be able to clearly see the Daphnia without getting too close to any potential harmful substances.
-Method:
1. On a cavity slide place some small strands of cotton wool on the cavity slide to prevent the Daphnia from moving too much when the caffeine solution is added.
2. Then collect a Daphnia with some water and place on the cavity slide.
3. Monitor the heart rate of this Daphnia for 1 minute and record the result in table as the control group. This is done because we need a resting heart rate to compare the results when the caffeine is added.
4. Repeat the control experiment two times recording the results as you go.
5.Then move through the concentrations of caffeine recording the results in the table and repeating each concentration so there are three results.
6. When a single concentration has been tested three times, place the Daphnia in the ‘Used Daphnia’ box of water and extract another Daphnia from the pond water.
-Materials:
1. Microscope – So I can see the full effect of caffeine on the heart rate of the Daphnia.
2. Stopwatch – So I measure the heart rate of each Daphnia with caffeine solutions for the same period of time (1 minute)
3. Cavity Slide – So I can hold the Daphnia in a small area so it cant move away from me when trying to measure the heart rate.
4. Strands of Cotton Wool – So I can prevent the Daphnia from moving fully when it reacts with the caffeine solution.
5. Pipette – So I can accurate collect one Daphnia needed and the correct levels of water and caffeine.
6. Glass Beakers – This is so I can have the correct measurements of water and caffeine concentration.
Results:
Table showing all the results obtained during the experiment plus the averages of beats of the Daphnia per minute for each concentration of caffeine.
Graph showing the average heart rate of the Daphnia for each concentration of caffeine used.
Discussion of Results
After conducting the experiment, I am able to see clearly that as predicted in my hypothesis, as the concentration of caffeine increased from no caffeine present to 0.5% caffeine , the average heart rate of the Daphnia per minute increased. These two variables are directly proportional to each other. For example when there is no caffeine present the Daphnia’s mean heart rate is 130.3 however when the Daphnia is in a 0.5% solution of caffeine its heart rate has increased to 167.3.
Conclusion
Having carried out this experiment fully, I am able to conclude that there is a correlation between the concentration of caffeine and the average beats per minute, the average beats per minute increases when the concentration of caffeine increases. This shows me that caffeine does have an effect on the heart rate as it speeds up when caffeine is reacting with Daphnia. Evidence of this is with no caffeine present the daphnia’s average heart beat is 130.3 bpm. Comparing this to the 0.5% caffeine solution the average heart rate is 167.3 bpm. So this clearly shows that caffeine does increase the heart rate. This is due to the neurotransmitters in the Daphnia being released in a greater quantity and more frequently so there more processes occurring in its body at a faster rate, resulting in a higher heart rate.
Evaluation
I think that the experiment went really well as I managed to progress onto testing all solutions available of caffeine in the time frame set. This has allowed me to gather more data than many of my fellow experimenters and so I am therefore able to have a more detailed conclusion with more evidence to back it up. Because of this reason alone I am pleased with how the experiment went. Furthermore I am able to say that there are no anomalies. This is good because it means all of my results are reliable and therefore my conclusions that I’ve drawn are valid. The one improvement I would make next time is to only time the heart rate for 30 seconds and then double the heart rate after that time to make it one minute. This is because I found it hard to constantly focus for a minute on the heart rate and could sometimes lose count and need to start over again. For an extended project of this practical experiment I believe it would be interesting to find out if substitutes for caffeine and similar products have the same effect as caffeine on the heart rate of Daphnia.
