Daphia should be handled with care through being collected and returned to the tank safely. Also they should be returned to their natural habitat as soon as possible after being experimented on ensuring they are to an extent back to homeostasis and are viewed as being able to live normally.
Care should be taken when handling glass apparatus to avoid breakages.
Attention should be paid around the microscope as the lenses at very delicate if ever in contact with the watch glass and also the light bulb can become extremely hot if left on for a long duration. The heat might affect their heart rate, it could reflect in the results.
Ethical issues
There are concerns about taking the daphia out of its own habitat; this then links to placing it in an unknown one i.e. the cotton wool. Also FEEDING the daphia with caffeine is classed by some to be immoral and threatening its life in some circumstances.
Potential Errors
Human errors include not being able to give an accurate measurement of the daphia’s heart rate as it is so fast and sometimes they would slightly move under the microscope disrupting counting methods. Also it’s hard to multitask being recording number of beats and watching the time at the same time it’s very easy to miss a couple of beats.
Physical errors include the daphia’s different sizes so doesn’t give a fair reading of the varied heart rates dependant on caffeine concentration.
It is accepted that caffeine effects humans and daphnia in similar ways, they are still different organisms so will be effected in slightly different ways. Although the general effects- increasing and decreasing heart rate- should be the same, the amount of variation will almost certainly be different, because humans are much larger than daphnia, a much larger quantity of caffeine would be required to produce the same degree of change in the heart rate. To get results that are completely accurate for humans, a large scale medical study would have to be undertaken.
When the daphnia is being observed under the microscope it is in close proximity to the lamp, which gives out heat, the little volume of water/concentrated caffeine concealing the daphnia, only requires a small amount of heat to raise the temperature. If the daphnia is under the microscope for just under five minutes, it’s likely to raise the temperature by several degrees, possibly increasing the daphnia’s heart rate. However this limitation can be counterbalanced as all daphia are under the same condition.
Apparatus
Daphia(water flees)
A plastic transfer pipette
A watch glass
A dissecting microscope
Beaker x2(one for used daphia, one for non-experimented daphia)
Distilled water
Electronic stopwatch
Concentrations of caffeine- 0.0(distilled water) 0.0625%, 0.125%, 0.25%, 0.5%
Method
Collected a selection of daphia in a beaker of distilled water, making sure the daphia were around the same size.
Tearing a minuscule piece off the cotton wool it was placed using tweezers into the watch glass.
Using the pipette one daphia was collected from the beaker and carefully placed onto the cotton wool, leaving some distilled water on the watch glass also, to keep the daphia in a comfortable environment.
Focusing the microscope onto the daphia,the heart was located behind it’s gut and above its brood pouches.
The stopwatch was then started and the heartbeat of the daphia was counting by spotting for 20 seconds.
The amounts of beats per 20 seconds was then multiplied by three to work out the daphia’s overall bpm.
This method was then repeated by replacing the distilled water in the watch glass with the different concentrations of caffeine after each assessment of daphia. Bearing in mind a new daphia was used after each assessment.
The results table is attached.
Analysis/conclusion
The results represented in the line graph have proven my hypothesis; they have given a positive correlation between the increase in caffeine concentration and the daphia’s heart rate. Suggesting their heart rate definitely does increase when the caffeine concentration is higher. For example a concentration of 0.0625% gave a heart rate reading of 265 bpm while 0.5% gave a reading of 376bpm, that’s an increase of 111bpm!
Evaluation
Although the hypothesis was proven to be correct, there were some anomalies found in the experiment (circled in the results table). These readings were much lower than the other repeats, this could be due to human error; misreading the heart beat due to the speed of contractions, or the size of the daphia; maybe the daphia used for that certain repeat could cope with the concentration of caffeine more effectively that the others for that certain concentration. Another explanation is that of the room temperature could have been at different temperatures at different times or at different areas in the room, for example near windows or radiators. This could have well affected the daphias heart rate.
Equipment was also found to affect the results, to get a true reading of a daphias heart rate, more technical equipment was needed. It was literally impossible to get an accurate reading from the control group of daphia, never mind when the heart rates increased with caffeine. Equipment could be improved by using better microscope lenses and the use of a ’clicker’ these pieces of apparatus would aid a better reading as I would of have a clear view of daphias heart rate to reading and a more sustainable way of counting heart contractions for the 20 second period.
