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The aim of this experiment is to research on the effect caffeine has on Daphnia heart rate.

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THE EFFECTS OF CAFFEINE CONCENTRATION ON DAPHNIA HEART RATE AIM The aim of this experiment is to research on the effect caffeine has on Daphnia heart rate. To enable this, a certain percentage of caffeine solution was tested on Daphnia (water fleas) as it will be a lot easier to monitor their heart rate due to their translucent body. This practical will help develop data representation and improve key practical skills. INTRODUCTION Caffeine is an odourless, slightly bitter alkaloid found in coffee, kola nuts and small amounts of cocoa. In humans, Caffeine acts as a stimulant on the central nervous system preventing drowsiness temporarily in order to keep the brain 'alert'. Caffeine is one of the world's most popularly used drugs and acts a mild diuretic in humans and animals. It will be unethical to carry out this experiment on humans as they have a high level tolerance to caffeine as it was proven in a recent experiment that higher concentrations of caffeine solution causes the heart to beat abnormal fast so an alternative source. Daphnia will be used to carry out this investigation as their resting heart rate is very high and this will air to provide rapid results. 1.1. Diagram of a typical Daphnia Daphnia are small water crustaceans which share a slight resemblance to water fleas and are mostly found in lakes and ponds. ...read more.


Keep all working surfaces clear and dry of spillages. Ethics Avoid using Concentration of caffeine solution at 1% causes paralysis of Daphnia and concentration at 2% causes death so use mild caffeine solution and at a lower percentage (0.5%). After experiment, Daphnia should be returned back to glass jar which contains pond water so it returns to its' normal heart rate. Health and safety Hand washing before and after practical. Lab coats need to be worn at all times (including safety glasses) and correct disposal of material. Avoid contact with eyes or mouth when handling chemicals. JUSTIFYING THE VALIDITY AND RELIABILITY OF THE METHOD CHOSEN Students will practice counting the heart rate of Daphnia before the start of the practical to familiarise themselves with the technique. Only suitable apparatus and experimental procedures should be followed to ensure precise and valid results. Results should be repeated several times and the method used for the practical followed carefully to avoid errors. Only the most precise equipment must be used if available (tally counters).Repeats should be kept at a minimum and anomalous results investigated. Measurements taken need to be cross checked with a partner to ensure precision. A TABLE TO SHOW THE EFFECT OF INCREASING % CAFFEINE SOLUTION ON DAPHNIA HEART RATE Caffeine % Heart rate BPM Test 1 Test 2 Test 3 Average 1 0 144, 192 223 218 215 2 0.1 208,260 264,234 210,266 240 3 0.2 204,214 264,318 284,240 ...read more.


Also there was a restricted use of caffeine solution. REDUCING ERRORS Extra care should be taken whilst using the caffeine solution so measurements need to be taken at eye level to ensure accurate results and the practical will need to be repeated again using tally counters. Furthermore, clear marked trays should be available to dispose of Daphnia in an appropriate manner with clear marked trays for 'fresh' and 'used' Daphnia so they don't get mixed up. CONCLUSION In conclusion, the overall results agree with the prediction that different doses of caffeine solution will increase Daphnia heart rate. This is because if the Daphnia's transparent body which ensures that we see results a lot faster than any other living organism. Although alternate sources were not available as it would have been termed unethical, the results would have been a lot slower if performed on humans or animals. IMPROVEMENTS Sufficient time will enable the students to complete the experiment and also cross-check every measurement and calculations with the aid of tally counters to improve accuracy of results. An increased percentage of caffeine solution would make it possible to carry out more repeats. FURTHERWORK It would be useful to repeat the practical with 0.3% of caffeine solution and also carry out the same experiment on humans and compare how caffeine affects their heart rate and also see medical expertise before carrying out this experiment. Resources www.elmhurst.chem/bio.co.uk As Salter's Nuffield Biology (Tehttp://www.fws.gov/midwest/pwlc/student%20work/aquatic%20inverts%205th%20grade_clip_image003.gifxt book) As Salter's coursework exemplar ...read more.

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