INTRODUCTION Every living organism has a metabolism. Metabolism is the sum of chemical reactions in one's body, including anabolic and catabolic processes (Pfleugal, 2014). These processes require energy which is obtained through the organism's respiration. Because an organism's respiration is linked to its energy consumption, researchers can observe changes in organisms' metabolism by observing their breathing rate. You can measure your breathing by observing the change in the concentration of oxygen or carbon dioxide in a closed environment. There are two categories of organisms: poikilotherms and homeotherms. The internal temperature of poikilotherms varies constantly because they depend on the external environment, whereas the internal temperature of homeotherms is kept relatively constant regardless of the external environment (Pfleugal, 2014). Because fish are poikilothermic, it is easy for researchers to observe changes in their metabolism due to changes in the external environment. One aspect of the fish's external environment that can be manipulated is the amount of caffeine present in the water. This experiment will examine changes in oxygen concentration within a chamber as a way to compare the respiration and metabolic rates of goldfish in two different fish aquatic environments: normal (control) and caffeinated. Because caffeine stimulates the respiratory center resulting in increased oxygen consumption, goldfish are expected to have a higher oxygen consumption and metabolic rate when exposed to caffeine (Brinley, 2014). Therefore, our hypothesis states that there will be a statistically significant change in oxygen consumption between the two environments, while our null hypothesis states that…middle of the paper…the first four different people handled the fish used for collect data. Each person handled the fish slightly differently, which could cause variations in anxiety and fear in the fish. A laboratory worker, like me, who has worked with fish for almost ten years, would probably cause less anxiety during the transfer, than someone who has never used a fishing net before. Fish that were roughly handled might have accelerated their heart rate and metabolism out of fear and anxiety, and therefore would have consumed a disproportionately large amount of oxygen, which might have skewed the results. To eliminate this potential source of error, we should have only one person handling the fish for all four groups. Overall, the data suggests that there is no significant difference between the metabolic rates of fish in normal water, when compared to fish exposed to caffeinated water..