Summary The respiratory system is responsible for regulating the exchange of gases between the body and the external environment. Differences in respiratory rate indirectly influence basal metabolic rate (BMR) by providing the components necessary for the formation of adenosine triphosphate (ATP) (Williams et al., 2011). Observation of gas exchange was measured and recorded for two mice (mus musculus) weighing 25 g and 27 g under the conditions of room temperature, cold temperature (8°C), and room temperature after fasting using a volumemeter. Oxygen consumption and carbon dioxide production rates were measured and used to calculate BMR, respiratory quotient (RQ), and oxidation rate. The mouse at room temperature was calculated to have a BMR of 2361.6 mm3/g/hour. In cold and fasting conditions, BMR values ​​decreased to 2246.4 mm3/g/hour and 2053.2 mm3/g/hour, respectively. Glucose oxidation rates increased with these treatments while fat oxidation rates decreased. Respiratory quotient (RQ) values ​​were calculated to determine the fuel source for metabolic activity. On a relative scale, protein or fat appeared to be the primary fuel source for all three treatments, although the 8°C mouse had the highest RQ and may have used relatively more glucose. It was also concluded that the BMR in mice is higher than in humans. Introduction In this experiment, mice were studied as examples of organisms that employ physiological mechanisms to maintain and regulate core body temperature. The breathometer uses the principle of water displacement. When the amount of gas in the restimeter changes, this will be reflected in an equivalent displacement of water in the pipette. Remember that at the same temperature and pressure,...... the central part of the paper... tends to be influenced by many other factors such as diseases, human presence or different external environments. Works Cited Akin , JA (2011) Homeostatic processes for thermoregulation. Nature Education Knowledge.3, 7.Biology 2A03 Lab 4 Respiratory Gas Exchange in a Mouse Lab Manual. Winter Term 2014 (2014). Department of Biology. McMaster University.Gordon, CJ (2012) The mouse: an “average” homeotherm. J Ther Bio.37, 286-290.Minke, B. and Maximilian, P. (2011) Rhodopsin as a thermosensor? Science.331, 1272-1273.Williams, C.T., Goropashnaya, A.V., Buck, C.L., Fedorov, V.B., Kohl, F., Lee, T.N., & Barnes, B.M. (2011). Hibernation above permafrost: effects of ambient temperature and season on the expression of metabolic genes in liver and brown adipose tissue of Arctic ground squirrels. J Experi Biol. 214, 1300-1306.