Investigating the effect of caffeine concentration on the heart rate of DaphniaIntroductionDaphnia, commonly known as water fleas, are tiny crustaceans that live in water. The diameter of adult female bodies is approximately 3-5 mm. The upper skeleton is transparent, making the internal organs visible. This allows us to calculate the heart rate of Daphnia by observing them under a microscope. Background Caffeine is found naturally in some plants such as coffee beans and tea leaves. Caffeine is also added to other drinks. Caffeinated drink (100 ml) Amount of caffeine (mg) Caffeine per 1 ml of drink Coffee 55 0.55 mg Tea 35 0.35 mg Coca Cola 15 0.15 mg Caffeine is known medically as trimethylzanthine. Caffeine acts as a cardiac stimulant, meaning it increases your heart rate. Adenosine is a natural chemical found in the body that binds to the respective adenosine receptors in the sinoatrial node and slows the activity of nerve cells. Caffeine also binds to these receptors, resulting in an increase in the activity of these nerve cells. Caffeine consumption also causes the release of the hormone adrenaline in the body, further increasing the speed of bodily functions. Caffeine also narrows blood vessels, which is why some headache medicines and painkillers contain sources of caffeine. 2 cups of strong coffee has been shown to increase heart rate in humans by approximately 15 beats per minute. Hypothesis As the concentration of caffeine increases, the heart rate of the daphnia also increases. Prediction The prediction for this experiment is that the higher the concentration of caffeine, the higher the heart rate in beats per minute. This is because caffeine acts as a stimulant, causing the hormone adrenaline b...... middle of paper ......from the lamp on cannot be easily controlled and could be a factor in the increased frequency cardiac. The heart rate may also increase due to the Daphnia's efforts to escape from the slide cavity due to limited water availability. Conclusion The results of the experiment indicate that the initial hypothesis was acceptable as the higher the concentration of caffeine, the higher the heart pressure. Daphnia yew. The results do not show this link in all cases; this could be due to the increase in temperature due to the heat produced by the microscope lamp, which leads to an increase in the heart rate of the Daphnia. This may explain the results for the 0.2% caffeine concentration. To improve the accuracy of the results, the same person should conduct all experiments as different people may count heart rate at different rates, leading to variations in the results.