CBL Interfacing

Shivering Isn't Enough: Heat Conservation In Homeotherms

Introduction

Have you ever been out in such cold weather that you start to shiver like crazy. This happens to be an important adaptation you have for building up body heat when you're really cold. Shivering works because the muscles which cause shivering must increase their rate of cell respiration. Most of the energy which is released from this cell respiration is released in the form of heat so shivering causes the release of heat from your muscle cells.

But shivering is not enough for most birds and mammals which live in cold habitats. These animals are homeothermic, meaning that they must keep their body temperatures fairly constant.

Birds and mammals have a wide variety of adaptations which they use to avoid the loss of too much heat. One way they maintain body heat is to regulate blood flow, sending enough blood to the skin to keep the surface cells alive, but not sending too much, which would result in the loss of too much heat.

Another mechanism is behavioral. Simply seeking a good shelter, such as a burrow, is one example of a behavior which helps these animals conserve heat.

The amount of insulation and the shape of the body play an important role in conserving heat. These are the two properties which we will examine in today's laboratory. We are going to conduct two experiments.

In the first experiment, we will consider the amount of insulation an animal has. We will use a beaker to represent a "naked" animal, and a beaker with cloth around it to represent an animal with fur or feathers. Equal volumes of hot water will be placed in each container. A temperature probe will be placed in each container and we will monitor the change in temperature over a period of time.

We will seek to answer the question-how quickly does each "animal" lose heat? State this question in the form of a hypothesis:

If....,then....

The independent variable in this experiment is time. The dependent variable is temperature.

In the second part of the experiment we will examine the effect of the shape of an animal on loss of body heat. For example, take the following two blocks.

They both have the same volume-64 mm3. However, their surface areas are different. The cube has a surface area of 96 mm2, while the rectangular solid has a surface area of 168 mm2.

In the second part of the lab we will seek to answer the question-How does increasing the surface area, but not the volume, affect how quickly an animal loses body heat? State this question in the form of a hypothesis:

If....,then......

The independent variable in this experiment is time. The dependent variable is temperature.

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