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Temperature regulation in mammals & birds.

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TEMPERATURE REGULATION IN MAMMALS & BIRDS Sahir Kara 11Hill Experiment Aim: To investigate how the shape and size of an organism affects the rate of temperature loss away from the organism. Background Knowledge: Most of the substances transported in the blood are carried dissolved in plasma. The main constituent of blood plasma is water (90% of blood plasma) (RESOURCE 1), from which heat can be lost by conduction, convection, radiation or evaporation. (RESOURCE 2) The limbs of a mammal or bird can easily be simulated using water-filled test tubes of differing sizes, to represent 'models' of a real life situation. The main method of transferring heat energy in a fluid (e.g.: water) is by convection. As a generalisation, most mammals and birds live in habitats where their body temperature is above that of their surroundings. (RESOURCE 3) Therefore, heat energy is principally lost from the bodies of mammals and birds by convecting and radiating away. Any liquid that is warmer than its surroundings will expand, so its particles occupy a greater volume than before (as they vibrate with the heat energy supplied). This in turn means that there is a decrease in density of the liquid, and the warmer particles move upwards (convection) and away (radiation) from the organism, through the blood vessels and protective skin. (RESOURCE 2) Mammals and birds (which are all warm-blooded organisms) have the ability to regulate their body temperatures, keeping their bodies within a set optimum range. Therefore, any heat energy lost is replaced by expending energy from food taken in, to keep body temperatures constant (37degrees in humans). (RESOURCE 1) Prediction: I predict that the larger the surface area / volume ratio of a 'model', the greater the rate of heat loss away from the simulation will be. Therefore, the surface area / volume ratio of a 'model' is directly proportional to the rate of heat loss away from the 'model'. ...read more.


* Test tube rack * Stopwatch * Thermometer Plan: Firstly, all apparatus required will be organised and arranged in the area in which the experiment will take place. The six test tubes will be taken one at a time, starting with the test tube numbered '1', and finishing with test tube '6'. Test tube '1' will be taken, a thermometer placed in it, and filled with boiling water taken directly from a kettle. The test tube will be placed in a test tube rack, and the stopwatch switched on when the temperature of the water reduces to 70�C. Continuous measurements of temperature of the water will be taken every 15 seconds, until 150 seconds (10 measurements) have been completed. The test tube will be thoroughly cleaned and dried, and the procedure repeated twice more for test tube '1'. The entire experiment will be repeated for test tubes '2', '3', '4', '5' and '6', taking 3 results for each different test tube. Resources Used: RESOURCE 1: Text Book: 'Coordinated Science - Biology' by 'Jones & Jones' RESOURCE 2: Text Book: 'Physics Study Guide' by 'Palfreyman & Maunder' RESOURCE 3: Information sheet: 'Temperature regulation in mammals and birds' RESOURCE 4: Text Book: 'Higher GCSE Mathematics' by 'D.Rayner' Results: Below shows the averages taken for temperature of the test tubes at the given time intervals: FOR RAW DATA TAKEN FROM THE EXPERIMENT, please see 'attached sheet 1'. Graphical Results: Firstly, 'time' (secs.) was plotted against 'temperature' (�C), in order to get a basic graphical result of the temperature of each test tube at every time interval. Then, in order to find how the shape and size (SA / Volume ratio) of a test tube affects the rate of temperature loss away from the test tube, a second graph was plotted (showing 'SA / Volume ratio' against 'rate of heat loss'). The rate of heat loss away from the model was found by drawing a tangent to the midpoint (75 seconds) of each line on the first graph. ...read more.


Although the readings have been found to be relatively inaccurate, I believe that the evidence collected was quite reliable. Obtaining 3 results for each SA / volume ratio of test tube made it possible to identify anomalous results, of which there seem to be 4 (highlighted grey on the above table). These anomalous results can be attributed to human error, movement of the test tube, and inaccuracies of the thermometers used. These anomalous results were averages of each of the 3 readings for every test tube, and were plotted on the first graph. The fact that the rates plotted on the second graph were up to 10.2% away from the line of best fit indicates that these anomalies may have contributed to the inaccuracies. Therefore, I believe that although inaccuracies found were vast, the evidence obtained is reliable enough to support a firm conclusion. This is because even though the results were inaccurate, the inaccuracies were consistent throughout, meaning that the overall outcome of the experiment was correct (although the actual readings may not have been). In order to improve the accuracy of the evidence further, the following changes could be made to the overall experiment: * Electronic temperature sensors, and precise data logging could have been used to measure the exact temperature at the given time intervals. * Electronic measuring devices could also have been used to measure the exact rate of heat loss away from the 'model' in each case. This is instead of drawing a tangent to each line on the first graph (to find the rate), which is a relatively inaccurate method. * The experiment could have been completed in an isolated area (where the movements of others would not have affected the results). To extend the experiment with new lines of enquiry, I could investigate how the volume of used water in one test tube affects the heat loss away from the model. Furthermore, I could experiment with real organisms, to investigate how heat loss away from their bodies is affected by different factors (such as external temperature etc.). Page 2 ...read more.

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