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Investigate the effect of huddling on heat loss.

Extracts from this document...

Introduction

Huddle investigation PLANNING A Aim: to investigate the effect of huddling on heat loss Hypotheses: 1. That the larger the huddle, the smaller the amount of heat lost. That is, an organism (test tube) on its own will lose more heat than if it were huddled in a group. In an experiment using test tubes, this will be supported by data which shows that a test tube by itself will lose more heat in the same amount of time than if it were in a huddle. 2. The temperature loss should decrease proportionally as the size of the huddle grows. 3. Also, the organism (test tube) in the centre of the huddle will lose less heat than an organism or test tube on the outside of the huddle. The reasoning behind this hypothesis is that as the huddle group grows in size, the amount of exposed 'surface area' will be reduced per test tube. Although in practice not every test tube is exposed, theoretically, this is a way of comparing huddles. Also, in a huddle of many organisms, or test tubes, if there is a centre test tube which is not 'exposed', it will be warmer than those on the periphery of the huddle. This hypothesis can be supported by data collected in the experiment by measuring the temperature of the centre of the huddle and the periphery of the huddle. The centre will be warmer because it has no surface area exposed to the outside. Huddling is a behavioural adaptation to the cold climate. 'Huddling' (in the case of penguins) is when a group of penguins stand closely together, nestling, in an attempt to reduce heat loss collectively as a group. This idea is effective because as a group, the penguins have lesser surface area exposed to the cold per penguin. Thousands of penguins have been seen in the Antarctic nestling together. ...read more.

Middle

of the 10 Test Tube Huddle Trial 1 Trial 2 Trial 3 Trial 4 Time (mins) Inner TT Outer TT Inner TT Outer TT Inner TT Outer TT Inner TT Outer TT 0 46.0 44.0 46.0 44.0 49.0 48.0 48.0 46.0 1 45.5 43.0 45.0 44.0 49.0 47.0 48.0 45.0 2 45.0 43.0 45.0 44.0 48.0 46.0 47.0 44.0 3 45.0 42.0 44.0 42.0 47.5 45.5 46.5 43.0 4 44.0 41.0 44.0 42.0 47.0 45.0 46.5 42.5 5 43.0 40.5 44.0 41.5 46.0 44.0 46.0 41.5 6 42.0 39.5 43.0 40.5 45.5 43.0 46.0 41.0 Physical Measurements of the huddle Table showing the physical measurements of the huddle and the test tubes 1-test tube 7-test tube huddle 10-test tube huddle Circumference (cm) 6.9 24.5 31.6 Length of test tube (cm) 15.0 DATA PROCESSING AND PRESENTATION Change in temperature in the experiments Table showing the change in temperature (Initial temperature - Final temperature) Temperature (�C) Trial 1 Trial 2 Trial 3 Trial 4 Average 1-test tube huddle 6.0 5.5 6.0 8.0 6.375 7 test-tube huddle - INNER test tube 2.5 1.5 2.0 3.0 2.250 7 test tube huddle - OUTER test tube 3.0 3.5 4.0 5.0 3.875 10 test-tube huddle - INNER test tube 4.0 3.0 3.5 2.0 3.125 10 test tube huddle - OUTER test tube 4.5 3.5 5.0 5.0 4.500 The variations in starting temperature in this case were ignored, as it was the initial temperature minus the final temperature calculated, thus the change was measured. It can be seen that the average change in the 1-test tube experiments were vastly different to those obtained in the other experiments. However this figure may be distorted by the result of Trial 4. If we look at the individual results from Trials 1 to 3, they are comparable with the results from the outer test tubes of the 10-test tube huddle. In this way, they do not look so atypical. ...read more.

Conclusion

We have to take note of the fact that glass absorbs and retains heat, and so the 'heat loss' we are attempting to measure may not be completely accurate. However, if we draw parallels between the test tube and skin of the animal, this may be accurate because the animal would retain the heat in its fur/feathers, thus not all the heat would be lost to the external environment. The heat loss in the water can be paralleled with the core temperature of the animal. I did not take into account the area exposed at the top of the test tubes, or at the bottom of the test tube because these would have been too difficult to measure. The meniscus of the water would prove difficult to measure, as would the curve of the bottom of the test tube. Furthermore, heat lost from the top would not be through glass (there is on glass at the top of the test tube). The bottom of the test tube is also thicker than the sides. Thus, heat lost from both these gaps would not be the same as heat lost from the sides. In order to keep the experiment consistent, these were ignored as part of the calculation for 'surface area'. Time restrictions must also be considered. Although the time the temperatures were measured over was fairly small (6 minutes), there were still palpable differences between the experiments, and the hypotheses could be supported with the data collected. The differences were not so small it was difficult to establish whether or not there was a pattern. However if the experiment was conducted over an even longer period of time (perhaps 10 minutes), the patterns may be even more distinct. Perhaps in the long run the 10-huddle may have performed better than the 7-huddle in heat loss. The temperature could also only be measured to 1 decimal place, but my partner and I decided to round up to the nearest half or whole number. This way, interpretation is clearer and reading the thermometer can be done with ease. ...read more.

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A high level of attention to detail is shown throughout this account. A clear understanding of concepts is evident. There are few errors.

Marked by teacher Adam Roberts 18/07/2013

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