Daphnia Experiment

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Effect of Caffeine on Daphnia Heart Rate:

Aim:
To investigate the effect of caffeine on the heart rate in Daphnia.

Hypothesis:
My hypothesis is that as the caffeine content increases, the heart rate if the Daphnia increases.

Equipment:
* Culture of water flea – Daphnia
* Caffeine of 5 different concentrations
* Microscope
* Counter
* Cavity Slide
* Pipettes
* Stop clock
* Distilled water
* Test tubes
* Petri dish

Method:
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

Variables:
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

Results:
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| |

Analysis:
The number of heart beats increase, as the caffeine concentration increases, as shown in the results.

Conclusion:
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...
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