TOEFL Speaking Task 3

In biology, the term “behavioral thermoregulation” refers to the actions an animal takes to control its body temperature by moving to different environments or changing its posture. This is distinct from physiological thermoregulation, which involves internal mechanisms like sweating or shivering. Behavioral thermoregulation allows animals to maintain an optimal temperature for survival and activity without expending extra energy. For example, ectotherms—animals that rely on external heat sources—often use this strategy to warm up or cool down, as they cannot generate their own body heat internally.

Professor: Let me give you a concrete example from a desert lizard species. During the cool morning, the lizard is sluggish because its body temperature is low. So, it emerges from its burrow and lies flat on a sun-warmed rock, exposing its entire belly to the surface. This maximizes heat absorption, and within an hour, its body temperature rises enough for it to hunt insects actively. But by midday, the desert sand becomes scorching hot—over 50 degrees Celsius. To avoid overheating, the lizard does not stay on the hot ground. Instead, it climbs up a vertical plant stem or a small bush, where the air temperature is cooler, and it angles its body so that only a small part touches the plant, reducing heat gain. It also lifts its tail and feet to minimize contact with the hot surface. By moving between these microhabitats and adjusting its posture, the lizard keeps its body temperature within a safe range, allowing it to remain active without frying or freezing.