Hypothesis: As the caffeine concentration rises, so does the mean heart rate of daphnia.
The Effect of Caffeine on the Heart Rate of Daphnia
Hypothesis:
As the caffeine concentration rises, so does the mean heart rate of daphnia.
Risk Assessment:
In this experiment there are the following risks both for the human that carries out the experiment and the daphnia:
- The human that carries out the experiment should be cautious not to touch the lamp with wet hands since it uses electricity.
- Also, be careful not to spill any of the pond water on the floor.
- As for the daphnia, there is a chance for them to die as when they are exposed to light, they are also exposed to heat in which they aren’t used to.
- Moreover, when they are given caffeine of a high concentration their heart may beat so fast that will cause their death.
- Furthermore, there is the risk of the daphnia to dry up, which may kill it in the middle of the experiment.
Method:
These are the steps that we followed when doing the experiment:
- Use a pipette to transfer the daphnia to a cavity slide containing pond water of known volume.
- Add some cotton fibres to the cavity slide and move them with a fine paint brush in such a way that the daphnia can’t move.
- Use a calculator to calculate the heart rate. Set its reading to zero and add 1 to the answer.
- One student will use a stopwatch to count 30 seconds which is the time during which the measurement of the heart rate will take place.
- Turn the microscope lamp on and locate the heart of the daphnia through the microscope.
- Measure the beat rate.
- Repeat steps 1-6 about 4 or 5 times and get an average. Then calculate the heart beats per minute (just by doubling the average).
- Clean the cavity slide using a tissue and make sure there is no pond water left.
- Use a pipette to transfer a known volume of caffeine solution of concentration 0.125% to the cavity slide.
- Transfer the daphnia to the cavity slide using the pipette.
- Measure the heart beats of daphnia per 30 seconds, following the same procedure as before.
- Repeat steps 9-11 using caffeine solutions of concentrations 0.25% and 0.5%