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Core PracticalDoes caffeine affect heart rate?)

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Core Practical Does caffeine affect heart rate? Introduction: -: Caffeine is the name of an alkaloid present in plants, such as coffee and tea.Caffeine is absorbed rapidly into the bloodstream from the gastro-intestinal tract. Throughout the body it increases metabolic rate by around 10%. Caffeine has many metabolic effects. For example, * It stimulates the central nervous system * It releases free fatty acids from adipose (fatty) tissue * It affects the kidneys, increasing urination, which can lead to dehydration * Increase heart beat Hypothesis: - My hypothesis was that the heartbeat of the water flea would increase when placed in a caffeine solution. ...read more.


We used two stop clocks to measure heartbeat of water flea in periods of 15 sec /min. We took five heartbeat readings. * This method was repeated six times each time a solution of caffeine was added. First we added .2%caffieine and placed a filter paper to stop the water evaporating. On the last occasion amount of caffeine that was used was 0.5% solution. No of heartbeats in 15 sec/min .RESULT:- Length of treatment(min) Time(min) 2 4 6 8 10 Treatment Control 43/172 61/244 62/248 66/264 65/276 0.2% Caffeine A 70/280 84/336 84/354 92/368 97/388 0.4% Caffeine B ...read more.


As the amount of caffeine was 0.1% the heart beat increased. However, when we used a 0.2% solution of caffeine the heartbeat decreased and at 0.3% caffeine the heartbeat increased, at 0.4% again decreased and at 0.5% again heartbeats decreased. My results do not seem accurate. There is probably some error in my readings. I need to do this experiment again. SUMMARY:- My results do not seem accurate and do not match my hypotheses. I need to repeat this experiment to get accurate results that more carefully test my hypotheses. RFRRENCE: - Salters -Nuffield Advanced biology (2005). ...read more.

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Response to the question

Introduction is good, sets out the background to the experiment and then proposes what the experiment is trying to find out in the hypothesis. I'd like to see a bit more scientific explanation behind why the heart beat increases when ...

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Response to the question

Introduction is good, sets out the background to the experiment and then proposes what the experiment is trying to find out in the hypothesis. I'd like to see a bit more scientific explanation behind why the heart beat increases when exposed to caffeine rather than just stating the different effects that caffeine has. Therefore, the background could be more focused into explaining the scientific reasoning behind the experiment, as could the hypothesis. Overall body of the method is quite clear and concise and the results presented in an appropriate way. The interpretation or discussion of the results is quite clear in the meaning although correct use of commas should have been used to separate the results out more.

Level of analysis

The level of analysis of results is good, and the discussion and then conclusion provide an accurate interpretation of the results. There could have been more scientific reasoning behind why the experiment went wrong and why the hypothesis should have been scientifically correct. They follow conventions for this level of work closely but the technical terms used are quite basic.

Quality of writing

In some instances the wrong punctuation has been used, or the wrong spelling, but this is very rare, overall spelling and punctuation okay. Wrong use of spacing in some instances, or misuse of one or two words.

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Reviewed by skatealexia 01/03/2012

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