Lab Section 8
4 Oct. 2005
In this experiment the oxygen consumption of a mouse in environments of varying temperatures was studied. The hypothesis behind this experiment was that more oxygen would be consumed at a lower temperature to maintain body heat. To measure the rate of oxygen consumption a mouse was given a specific amount of oxygen. The amount consumed in a specific time was measured and compared to the rates at a colder temperature. Just as expected, oxygen was consumed more rapidly at a lower temperature. This would lead to the conclusion that more oxygen is required to maintain homeostasis in a system. Introduction
Metabolic rate is a measurement of energy used by an animal within a specific period of time. This can be measured in a number of ways: recording an animal’s heat loss with a calorimeter, determining the amount of carbon dioxide an animal produces, recording an animal’s food intake compared to the food’s chemical energy potential and the amount of waste the animal creates, and finally by measuring the amount of oxygen a test subject consumes during a given period of time1. The mouse used in the experiment is an endotherm. Endotherms use energy produced through metabolism to maintain and generate consistent body heat2. Endotherms also generally have a higher metabolic rate than ectotherms (organisms that gain heat from their surroundings) 1. Factors other than endothermic or ectothermic status also influence metabolic rate, including size and activity. Size is inversely proportional to metabolic rate. Higher metabolic rates have been found in small endothermic animals; however there is no concrete explanation for this finding1. Activity also affects metabolic rate. The longer and activity lasts the lower the maximum metabolic rate becomes. In the absence of activity an organism is said to be either at its basal metabolic rate (for endotherms) or is standard metabolic rate (for ectotherms). These rates can be affected by many outside factors including time, temperature, nourishment, and physical characteristics1. Metabolic rate is also a way of maintaining homeostasis in an organism. Homeostasis is the relationship between the body’s internal regulatory factors (for example, metabolic rate) and outside factors that affect an organism’s internal systems1. Multicellular organisms cannot survive without a homeostatic internal environment3. Without thermoregulation brought about by a constant metabolic rate reactions and interactions between bodily chemicals would not function properly and homeostasis would no longer exist. In other words, an endothermic organism cannot carry on normal functions if it internal temperature varies greatly from the homeostatic norm1. One method of thermoregulation is through evaporation. Water on the surface of an organism absorbs a great deal of heat as it evaporates, thus carrying heat away from the body and maintaining the body’s internal temperature. Other methods of thermoregulation include conduction, convection, and radiation1. In order for the metabolic rate to be maintained there must be a supply of energy to meet fluctuating demands. This energy is produced by the controlled oxidation of sugars, starches and other energy yielding organic molecules. In short, oxygen and an organic molecule react to produce water, carbon dioxide and energy2. The energy produced is used to maintain the metabolic rate. Therefore, if the amount of oxygen consumed can be determined the average metabolic rate can be estimated as can fluctuations therein. Therefore, concerning the oxygen consumption experiment; as the need for energy increases with lowering surrounding temperatures, the consumption of oxygen will increase in order to maintain homeostasis. Materials and Methods
A respirometer was the primary device used in this experiment. This piece of...