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Investigation into the factors which affect the heart rate in daphnia.

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Mandeep Kamboo Investigation into the factors which affect the heart rate in daphnia Introduction I am going to investigate how various chemicals such as alcohol, aspirin and caffeine have an effect on the rate of heartbeat in daphnia. Daphnia are aquatic crustaceans, who live in the water. They have a simple heart which is visible under the microscope. Prediction I predict that caffeine will increase the number of heartbeats per minute because caffeine increases the blood pressure in humans, which stimulates the central nervous system and stimulates the action of the heart and lungs. Therefore, I would expect caffeine to also stimulate the heart and nervous system in daphnia. Caffeine 0.75% will have the highest amount of heartbeats per minute. Aspirin slows down the number of heartbeats, per minute therefore for aspirin 0.1% the heartbeats will be slower compared to caffeine 0.75% as caffeine has greater effect on heartbeat then aspirin. The higher the concentration of caffeine, the higher amount of heartbeats per minute. Apparatus * Cavity slide * Microscope * Daphnia * Stopwatch * Counter * Beaker * Pipette * Caffeine (0.01%, 0.1%, 0.05%, 0.75%) * Aspirin (0.05%, 0.75%, 0.1%.) ...read more.


The caffeine will be removed using a pipette, ready for the next experiment. Then water will be put onto the daphnia to allow its heartbeat to reach normal rate. This will be done with an interval of 1 minute each time. The next solution will be placed onto the daphnia and the experiment will be repeated using aspirin. Different concentrations of caffeine and aspirin (e.g. 0.01%, 0.1%, 0.05%, 0.75%), will be used. This is to see which amount has the greater effect on the heartbeat. Results Time taken in minute Water Aspirin 0.05% Aspirin 0.1% Aspirin 0.75% 1 200 224 216 272 2 164 244 232 256 3 192 256 244 252 4 192 252 260 232 5 184 240 260 264 6 188 252 212 260 7 164 208 276 212 8 192 192 240 252 9 196 216 208 260 10 232 272 252 272 Average = 190 Average = 236 Average = 240 Average =253 Time taken in minute Caffeine 0.01% Caffeine 0.05% Caffeine 0.1% Caffeine 0.75% 1 235 252 260 212 2 204 228 248 276 3 240 268 232 292 4 224 252 224 276 5 236 196 276 280 6 244 220 224 236 7 264 264 200 260 8 196 252 260 256 9 200 ...read more.


It was difficult to compare the results as I started off with different heartrates for each variable, this therefore means that I will have to compare the averages. If I was to repeat this experiment again different condition would be used e.g. alcohol, as I would want to see what effect it has on the daphnia's heartbeat. I would also change the temperature, to see at which temperature the daphnia's heartrate is stimulated the most and I would use different daphnia's this is because I would obtain more accurate results. There are certain factors which could have had an effect on the results e.g. the heat of the light bulb, the effect of the temperature could have also caused the daphnia's heartrate to stimulate. When placing water with the pipette after each test so that the heartrate could go back to normal, that might not have been very accurate. This therefore means that if the experiment could be repeated I would need some level of accuracy e.g. the same amount of solution would be needed for each solution. But overall I felt my results were quite accurate as it showed which solution i.e. caffeine or aspirin was more stimulant on the daphnia's heartbeat. The rate of heartbeat was affected more by caffeine than aspirin. ...read more.

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