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Daphnia experiment - Does caffeine affect heart rate?

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Introduction

Does caffeine affect heart rate? Aim To investigate the effect of caffeine on the heart rate of Daphnia (water flea). Plants produce caffeine as an insecticide (a way of getting rid of insects). Cocoa, produced in South America, coffee in Africa and tea produced in Asia have all been throughout the words to keep us all going. Caffeine is also used as a flavour enhancer in coca cola and other soft drinks. It has been proved very useful in medicinal uses in aspirin preparations and is found in weight loss drugs. Caffeine is a drug that stimulates the body and causes an increases amount of stimulatory neurotransmitters to be released. At high levels of caffeine consumption it can and has been linked to restlessness, insomnia and anxiety, therefore this causes raised stress and blood pressure. This can then lead to heart and circulation difficulties. Daphnia are small planktonic crustaceans, measuring between 0.2-0.5mm in length. Their heart can be seen though magnification, therefore their heartbeat can be counted. Hypothesis The amount of caffeine in the blood will determine the heart arte of the daphnia. It will be directly proportional to each other, therefore resulting in, as the caffeine solution increases, the heart rate of the daphnia will also increase. ...read more.

Middle

The age of the daphnia being used cannot be controlled. In this experiment it will be appropriate to use a 10ml pipette to measure volumes than it would be to use a 1ml pipette. For this experiment the pipette measurement is the correct degree of accuracy being used. The systematic errors in this experiment could be reading volumes in pipettes could cause faulty measurements. Personal bias of the person taking the measurements can also introduce systematic errors. For example, expecting higher results with caffeine when investigating the effect of caffeine on the heart rate of daphnia could lead to higher results when caffeine is in the solution. This is best avoided by using a blind testing method where the investigator recording the results does not know which treatment contains the caffeine solution and which is the control. The random errors may be reading the volumes, or not precisely measuring out the volumes. Carelessness can produce random errors, like not concentrating on using exactly the same procedure each time. Also, giving the daphnia an equal amount of time in the caffeine solutions, before testing. In every experiment, only the reliable and accurate results are useful. The more trials that are done, the average will be a fairly good result and more reliable. ...read more.

Conclusion

5 297 300 299 0.5 1 296 126 211 2 297 358 328 3 444 285 365 4 483 382 433 5 304 314 309 Analysis of results Group 1 and group 5's data were the most unreliable because there were peaks that were off the average points. Group 5 had miscounted data at 159. Moreover Group 1 had 2 sets of data that seemed anomalous, which were 381 and 211. The most reliable data, which can be seen from the graph, were from Group 4. The points steadily rise until it reaches its peak. Conclusion When looking at the results that I have obtained I can see that when ?adding more caffeine concentration to the water flea, the heart will ?also increase and there fore the prediction that it will be directly ?proportional is correct. This change in heart rate is due to caffeine being a drug that stimulates the body, and increases the amount of stimulatory neurotransmitters released. With high levels of caffeine, restlessness, anxiety, and insomnia can arise, causing an increase in the heart rate. If I were to conduct this experiment again I would try and have a more accurate way to measure the heartbeats, a larger sample size of daphnia, and run more trials. I would also have a wider range of caffeine levels to test. Rianne Malcolm 12H ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a well written report that covers the necessary information needed for this investigation.
1. The practical is well set up but some subheadings are wrong.
2. The data is well presented.
3. The analysis of the results is very brief and needs more detail.
4. The report is missing an evaluation.
***

Marked by teacher Luke Smithen 23/07/2013

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