To investigate the effect of caffeine on the heart rate in Daphnia.
My hypothesis is that as the caffeine content increases, the heart rate if the Daphnia increases.
* Culture of water flea – Daphnia
* Caffeine of 5 different concentrations
* Cavity Slide
* Stop clock
* Distilled water
* Test tubes
* Petri dish
1. Remove one Daphnia and place it in the cavity slide
2. Remove the pond water and replace it with distilled water 3. Leave it for 5 minutes to acclimatize, then observe the heart rate under the microscope for 30 seconds, multiply the number by 2 to calculate the beats/min 4. Repeat with 2 more Daphnia
5. Repeat again, this time with a small concentration of caffeine solution in place of distilled water 6. Carry out for 5 more concentrations of caffeine
Independent Variables: - Caffeine concentration
Dependent Variables: - Heart rate of Daphnia
Other Variables to be controlled: - Temperature
- Volume of solutions
- Stress of Daphnia
- Size of Daphnia
- Time of acclimatisation
Daphnia| Caffeine concentration/arbitrary units| Number of heart beats/min| Mean heart rate (bpm)| A| 0 (control)| 45| 48.75|
| 5| 50| |
| 10| 53| |
| 15| 47| |
B| 0 (control)| 68| 73.25|
| 5| 73| |
| 10| 76| |
| 15| 76| |
C| 0 (control)| 96| 99|
| 5| 101| |
| 10| 99| |
| 15| 100| |
The number of heart beats increase, as the caffeine concentration increases, as shown in the results.
The hypothesis was correct as the heart beat did increase as the caffeine concentration increased. However, this experiment could have been more fair due to the following: * All the daphnia used...