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How does caffeine affect the heart rate of Daphnia?

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Introduction

´╗┐Mohamed Ahmed Does caffeine affect heart rate? The purpose of this experiment is to investigate the effect of caffeine on the heart rate of Daphnia (water fleas). Daphnia are tiny aquatic invertebrates that are suitable for this experiment because they?re abundant, easily obtained, transparent and have very simple nervous system. Hypothesis: I think that a Daphnia subjected to a caffeine solution will show a rise in heart rate, this rise in heart rate should reflect the concentration of caffeine in a given solution. This is because caffeine is a stimulant that speeds up the body affecting the nervous system and rate in which the nerve pulses are sent and received in humans. I produced a detailed plan for an experiment that allowed me to test my hypothesis using the following materials: 1. Pipettes 2. Test tubes 3. Stop clock 4. Microscope 1. Daphnia 2. Cavity slides 3. Distilled water 4. ...read more.

Middle

We will handle cavity slides and test tubes carefully to prevent breakage 2. Be cautious not to touch the lamp with wet hands since it uses electricity 3. Be careful not to spill any of the testing solutions on the floor. There are some ethical issues involved in using these invertebrates. Many people believe that it?s unethical to cause distress or suffering to any living organism - e.g. by subjecting them to extremes of temperature or depriving them of food. I will take this into account whilst doing my experiment by not putting the microscope on a high power. Some people believe it?s more acceptable to perform experiments on invertebrates (like Daphnia) than vertebrates (like dogs and monkeys). This is because they?re considered to be simpler organisms than vertebrates. For example they have a much less sophisticated nervous system, which could mean that they feel less pain (or no pain). ...read more.

Conclusion

To determine the heart rate, the beats are counted in pulses under a microscope and recorded using a hand counter. This is accurate; however a margin of systematic error should be accounted for in the results. We will make sure measurements are precise and accurate by making the tests repeatable. Results Concentration of Caffeine Solution (%) Daphnia?s pulse counted in 20 seconds (x3 for 1 min) Daphnia?s pulse counted in 20 seconds (x3 for 1 min) Test 1 Test 2 0 54 51 0.1 75 72 0.2 108 102 0.3 135 138 0.4 192 180 0.5 261 237 Conclusion ? I stated in my hypothesis that I think that a Daphnia subjected to a caffeine solution will show a rise in heart rate. The results obtained by my group and I indicates that my hypothesis was correct because the more concentrated the caffeine solution was, the higher the heart rate of the daphnia; at 0.1 % caffeine solution the mean heart rate of the Daphnia was 53 beats per minute; with 0.3 % caffeine solution the mean heart rate of the Daphnia was 173 beats per minute. ...read more.

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