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Experiment to determine whether caffeine can have an effect on the heart rate.

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Experiment to determine whether caffeine can have an effect on the heart rate. Background knowledge Caffeine is an xanthine alkaloid, that is a known steroid that can promote hypertension and hyperactivity. It is commonly used in drinks that are supposed to "pick you up". They are caffeine rich and give the drinker a boost of energy. It also has medicinal uses in aspirin and some weight loss drugs. It acts as a stimulant and increases the number of stimulatory neurotransmitters released. Due to this it has been linked to restlessness, insomnia, twitching and raised levels of stress, which leads to higher blood pressure. Caffeine is an addictive drug; people who consume large amounts of caffeine often have withdrawal symptoms after extended periods of time. These symptoms are similar to those found in heroin addicts; just not as severe. Excessive consumption over longer periods of time can produce peptic ulcers, due to an increase in stomach acid production. It is produced naturally in over 60 plants as a pesticide, which paralyzes and kills certain insects that feed upon it. Hypothesis: Due to the information stated in the background knowledge, I can predict that caffeine will induce a higher heart rate in the Daphnia, as opposed to daphnia exposed to no caffeine. ...read more.


In order to maintain accurate results, the fleas should be of equal size. The same flea must not be used for more than one caffeine involved experiment as the heart rate of the flea might still be affected and a caffeine overdose may harm the flea. Method: Apparatus: * Culture of Daphnia * Cavity slides * Dropping pipettes. * Distilled water * Caffeine solution * Cotton wool * Beakers * Measuring cylinders * Syringe * Stop clock/timer * Paper towels * Microscope 1. Set up the microscope and all the equipment. Make sure it is all clan to prevent contamination of caffeine solution. 2. Dilute the caffeine solution to the required concentrations. 3. Take a Daphnia out of the pond culture and place it onto the cotton wool in the cavity slide containing distilled water. This is the control experiment. 4. Start counting the beats of the Daphnia's heart when it is I the distilled water. 5. Remove the distilled water and cotton wool and replace it with fresh cotton wool and the caffeine solution that is being tested. (Ensure that the Daphnia is on top of the cotton wool at all times and, during the replacing of cotton wool, is not distressed too much as this can increase the heart rate of the Daphnia) 6. ...read more.


Other experiments conducted on animals have produced more dramatic results. Spiders were given caffeine and allowed to build their web whilst others were not given any caffeine. The results, shown left, are plain to see. This is because caffeine is a stimulant, which can affect the central nervous system and the heart. It has been likened to the hormone adrenalin, in that it can increase a person's mental alertness in moderation and can affect stamina and the central nervous system. The results are not as valid as I would have previously expected. As we did not have enough time, all of the experiments could not be carried out effectively, or repeated enough times to achieve more accurate results. Human error would have played an important part in this experiment as the recording of the data was carried out by eye. The reaction times of the people counting the number of beats per 15 seconds would have had an influence as the Daphnia's heartbeat could be very irregular. To reduce this in future experiments, more efficient equipment should be used such as a high speed camera that can be reviewed later to count exactly how many beats there were in the time frame. The experiment should also be repeated more times in order to achieve more accurate results and an effective average. ...read more.

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