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# I think that caffeine enters the daphnia's body then the heart rate will increase dramatically

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Introduction

Does Caffeine Affect Heart Rate Hypothesis: I think that caffeine enters the daphnia's body then the heart rate will increase dramatically. This is because caffeine acts as a stimulant making muscles work faster. I will count the heart beats from daphnia in water and then in caffeine and see the difference. Suitable equipment: We used a pipette to pick up the daphnia. This could injure the daphnia. Also this could startle the daphnia which would increase its heart rate therefore making it an unfair test. Risk assessment: Ethical Issues: You have to use ice water on a separate slide underneath the daphnia so that the heat from the microscope doesn't burn it. Use cotton wool to stop the Daphnia from moving about to much, this makes it easier to keep the daphnia to see and count the heart beats. ...read more.

Middle

Reliability and validity: I don't think that my results were very valid or reliable. It was very hard to count the heart beats because the heart was eating to fast to count. You might not always get the right beat for the heart either. Therefore I could have counted the heart beats wrong. One way that you could solve this problem is to use strobe lighting and set it so that it looked like the heart wasn't moving at all. You would then know that the heart was beating at the same speed as the strobe lighting. This would mean that the heart beat count was more reliable and valid. Errors There is a possibility of random error when you are counting the heart beats. ...read more.

Conclusion

I had no anomalous results. My non caffeine results had a range of 14 and my caffeine results had a range of 78 which is larger. This is because it was harder to count the heart beats when the heart was beating faster. Conclusion I think that the caffeine makes the heart of the daphnia beat faster this mean that more blood is being pumped from the heart around the body. For further investigation we could try the experiment on larger animals such as dogs or humans. Or you could try the experiment on the same animal but with different concentrations of caffeine. If I was to experiment the investigation further I would find an animal which it is easier to measure the heart rate on such a human where you can use a machine. ?? ?? ?? ?? Emily Lewis Core Practical 31/12/2006 ...read more.

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