How does caffeine affect heart rate?

Health and safety

• Wash your hand thoroughly after the experiment
• Wash all the place where pond water fell
• Do not mix water with electricity
• Keep the area dry.
• Broken glass should be always put in to the glass bin

Errors

Systematic errors occur due to incorrectly calibrated equipment or a fault in the experimental procedure used. Personal bias of the person taking measurements can also introduce systematic errors. To reduce the personal bias, some people are given original caffeine and others are given pond water. The teacher and the student who prepared will be the only persons who knew which treatment contain caffeine and which one contained the control. Then we are made to exchange the slides.

Random errors can occur by not following the standard procedure also carelessness can produce random errors as well.

Implementing the plan

1. Set up microscope in pairs.
2. Set up the cavity slides
3. Take one slide and add 2-3 drops of ice water in it, this will later act as the heat sink.
4. Then place another on the top, facing the converging side up.
5. Using pipette, transfer a large daphnia from the pond water to the cavity slide.
6. Providing enough water will help to have sufficient amount of oxygen to the daphnia
7. Place few straits of cotton wool on the cavity slide to prevent the movement of the flea.
8. View the water flea under a low power compound microscope

9. Focus on its heart which can be seen through its translucent body
10. Use a stop watch to record the number of heart beats per minute
11. One person count beats while other tells time
12. Tap a pencil on a paper and count up the pencil marks at the end of the time period
13. Record the heart rate at intervals of 2 minutes over a period of 10 min
14. It is possible to take 30 seconds bat and multiply it with 2 to get a minutes beat
15. Repeat the experiment
16. Take average to get accuracy
17. Clean up all the places and replace all the things used in proper way

Animal welfare

We should always be aware of animal welfare. We should know that even a small daphnia has its role in the ecosystem. So we should not try to kill them during our experiments. Always check that there is enough water in the cavity slide so that the daphnia gets sufficient oxygen. Put the lights off of the microscope, when it is not in use. During the experiment make sure that the daphnia is stress free. The heating effect of light may give stress to the daphnia leading to increase its heart rate. After use they should always go to a beaker with pond water labelled used daphnia, and later they are settled in the pond.

Variables that had an effect that can be controlled

Dependent variable- heart rate of daphnia

Independent variables:

• Temperature of the water

• Straits of cotton wool that can cause strain in daphnia

• Heat produce by the light of the microscope

• Size, age and gender of daphnia

• Oxygen level

• Gender of the student who done the experiment

• Room temperature

• Time limit (variation in time count)

RESULS TABLE

Heart beats of a large daphnia per 30 second

Graph

Validity /Reliability of the Results

I think the results I got are reliable, because this activity is done 5 times by each student and there were 6 groups to do this so this is repeated 10 times and taken the average.

In order to make the results valid I have controlled the variables that I think would have made an effect .the graph shows a trend that caffeine has an effect on heart rate.

Summary

It is clear from the results table and the graph that the heart rate of daphnia is high for those which was on caffeine. So I conclude that caffeine has a positive effect on heart rate .it can increase the heart rate. The results table shows that, as the time increases the heart rate also increases, this is because of the stress that it experiences.

References

.gmu.edu/biology