INTRODUCTIONEvery living organism has a metabolism. Metabolism is the sum of chemical reactions in the body, including anabolic and catabolic processes (Pfleugal, 2014). These processes require energy obtained by the body's respiration. Because an organism's respiration is linked to its energy consumption, researchers can observe changes in organisms' metabolism by examining their breathing rate. It is possible to measure respiration by observing either the evolution of the oxygen concentration or that of carbon dioxide in a closed environment. There are two categories of organisms: poikilotherms and homeotherms. The internal temperature of poikilotherms varies constantly as they depend on the external environment, while the internal temperature of homeotherms is kept relatively constant regardless of the external environment (Pfleugal, 2014). Because fish are poikilotherms, 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 inside a chamber as a method of comparing the respiration and metabolic rates of goldfish in two different fish water environments: regular (control) and caffeinated. Since caffeine stimulates the respiratory center, leading to increased oxygen consumption, goldfish are predicted to have higher oxygen consumption and metabolic rate when exposed to caffeine (Brinley, 2014 ). Thus, our hypothesis indicates that there will be a statistically significant change in oxygen consumption between the two environments, and our null hypothesis indicates that...... middle of paper ...... four different people have manipulated fish that was used to collect data. Each person handled the fish a little differently, which could cause variations in anxiety and fear in the fish. A lab worker, like me, who has worked with fish for almost ten years, would probably have less anxiety during the transfer than someone who has never used a fishing net before. Roughly handled fish could have increased their heart rate and metabolism out of fear and anxiety, and thus consumed a disproportionate amount of oxygen, which could skew the results. To eliminate this potential source of error, only one person would need to handle fish from all four groups. Overall, the data suggest that there is no significant difference between the metabolic rates of fish in ordinary fish water, compared to the metabolic rates of fish. fish exposed to caffeinated water.