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THERMOREGULATION

Desert organisms experience temperature extremes. Yet the temperature of their body affects their life functions -- too hot and the proteins in their body breakdown (eventually leading to death); too cold and their body functions slow down. Thus plants and animals have various strategies to regulate their body temperature for optimum performance.

Concepts:

• Van't Hoff's Rule: for every temperature rise of 10 degrees C, rate of biochemical reactions (most body functions) doubles, up to a point (when proteins break down).
• Energy Pie: all energy taken in by plants and animals is portioned out to the following areas -- growth, reproduction, activity, maintenance, and storage. Savings in one area (e.g., maintenance which includes thermoregulation) means more energy can be diverted to other areas (e.g., storage for hard times later).

Types of Thermoregulation:

• Behavioral Thermoregulation: using posture, orientation, and microclimate selection to regulate body temperature. For example, a lizard that wants to heat up will spread eagle (posture) on the top of a hot rock (microclimate) and turn its entire back to the sun (orientation).
• Physiological Thermoregulation: altering metabolic generation of heat to regulate body temperature.

Types of Animals based on means of thermoregulation:

• Ectotherms: animals whose principal source of body heat is the environment. Includes essentially all animals except birds and mammals.
• Endotherms: animals whose principal source of body heat is from their own body generating heat metabolically. Birds and mammals are endotherms.