Final answer:
The small lizard's behavior of sunbathing and seeking shade is essential for maintaining homeostasis by thermoregulating its body temperature, which involves speeding up their physiological processes when warm and conserving resources during estivation when it cools down.
Step-by-step explanation:
A small lizard utilizes the warmth of the sun to elevate its body temperature and thereby improve its physiological functions, such as muscle movement, which are more efficient at higher temperatures. Later in the day, it seeks a shaded area to cool down. This behavior is crucial for the lizard to maintain homeostasis, which is the regulation of a stable internal environment despite external changes. Homeostasis in reptiles like this lizard often involves behavioral adaptations to control body temperature, as they are ectothermic animals whose body temperature varies with the environment.
When too cold, the lizard increases its temperature by basking in the sun which makes it more agile and less vulnerable to predation; when too hot, it conserves energy and water by resting in the shade and slows down its metabolic processes, like breathing and heart rate, entering a state known as estivation.