Equipment/Setup
Method
- Place a few strands of cotton wool onto the cavity slide.
- Using a pipette place a water flea and surrounding water into the cavity slide and blot excess water away.
- Wait until flea attaches itself.
- Place under the microscope and adjust
- As working in a pair, one member times for one minute whilst the other member counts the heart rate by making pencil mark for every heart beat and then counting up the marks.
- Repeat at least three times to get a range of readings.
- Then repeat this after adding a few drops of the caffeine water.
- Average out the respective results to find an standard result.
Whilst doing this experiment, you have to be very careful with the equipment. The microscope is expensive and may break quite easily as well as all other glassware.
As these fleas are living creatures, there are some ethical matters attached to this experiment. Though we are bringing them out of their natural environment, we are using pond water, which is close to their natural habitat.
In addition to this, these fleas are to be returned to their environment when the experiment is over.
Results
I believe these results reflect a correct hypothesis.
There is a significant increase in the heart rate when caffeine is added.
I believe these results are also valid as they reflect what they are supposed to. There is a considerable difference in heart rate with compared to without caffeine. Which is correct.
These results are repeatable, as proved by the repeating f the tests, which shows that they are reliable.
In comparison to the class values, the results have a range of about 37 beats. I am not sure if that is large or small for this type of experiment.
This could be due to human error.
The person counting could have missed a few beats or maybe even over compensated for a few beats. These can easily distort results and produce a wider spread of values than that which is acceptable.
Other errors include the stopwatch being calibrated incorrectly but this would only produce systematic errors, which may not be too much of a problem unless a significant percentage of stop clocks were calibrated incorrectly. This could give some pairs a higher/lower value for the heart rate. (if +or- a second, could add a significant amount of extra/less heart beats in the time span)
My average results for TEST A were slightly below the class average, whereas for TEST B, they were above.
