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CBL Interfacing

Shivering Isn't Enough: Heat Conservation In Homeotherms


Teacher Tips

Length of Lab: two 40-45 minute periods.

1. Remind students to fully insert the I/O cable in the CBL and TI 82.

2. At the onset of the experiment, both set ups should be at the same temperature. In the second experiment, with different shaped "animals", students should use one graduated cylinder for measuring the water which goes into each animal. Students may be tempted to measure the first quantity of water and place it in the beaker and then measure the second quantity of water and leave it in the graduated cylinder. They should pour the second quantity into a second graduated cylinder. Each transfer of water is accompanied by a temperature drop. Avoiding a second transfer will result in the "elongated animal" starting out at a higher temperature.

3. For the second experiment, the layer of oil should be place on the surface of the water immediately to avoid a significant temperature drop due to evaporation before the experiment begins.

4. The probes should be in the same approximate position in each set up to reduce the number of potential variables.

Here is some sample data showing an insulated animal (beaker with scarf) vs. a non-insulated animal (beaker without scarf).

Answer To Questions

:

1) For each animal tested, describe the relationship between temperature and time. In each experiment, which animals tend to lose heat most easily? Base your answers on the slopes which you determined.

For all four animals the temperature drops. It drops most quickly at the beginning and then more slowly as time progresses. The slopes are all negative, but the slope of the non insulated animal is more negative (lower) than the slope of the insulated animal. The slope of the elongated animal is more negative (lower) than the slope of the box shape animal.

2) How does the layer of insulation affect heat loss in your animals? How does the shape of the animal affect heat loss in your animals? Do your results support or refute your hypotheses? Explain.

Insulation and a smaller surface area to volume ratio reduce heat loss. Whether or not this supports the students' hypothesis will depend on what hypothesis they chose to make.

3) Consider the four animals drawn below. One rabbit and one fox lives in a cold weather climate where it must conserve heat. One rabbit and one fox lives in a warm weather climate. Based on your results, match the four animals to their climates. Be sure to explain the basis of your choices.

A. show picture of desert jack rabbit.

B. show picture of snow shoe hare.

C. show picture of arctic fox.

D. show picture of desert fox.

The desert fox and desert jack rabbit, with more elongated limbs and ears will lose heat more readily than the arctic fox and snow shoe hair which have shorter legs and ears and a thicker coat of fur.

4) Describe some ways in which homeotherms conserve heat which are not covered in this lab.

Some other ways in which homeotherms conserve heat is by regulating blood flow to their skin and their extremities, counter current blood flow in long legged wading birds, shivering, oil coating to keep cold water away from skin, coat color, hibernation, and behavioral, including seeking shelter.

5) Describe some ways in which homeotherms lose excess heat which are not covered in this lab.

Animals lose excess heat through sweating (evaporation), panting (evaporation), regulating blood flow bringing more heat to the surface and through behavioral cooling mechanisms such as heat avoidance (seeking shelter during the day) or sitting in the shade.

6) What are the differences between homeothermic and poikilothermic animals.

Homeothermic animals (birds and mammals) maintain a constant body temperature while the body temperature of poikilothermic organisms fluctuates with the environment.

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