Which of the following describes a lack of regular pattern in organisms in unchanging habitats?

The term that describes a lack of regular pattern in organisms within unchanging habitats is "arrhythmic." This concept refers to behaviors or biological rhythms that do not display a predictable cycle or pattern. In stable environments, one might expect certain behaviors or activities to follow a regular rhythm, but when organisms are arrhythmic, their actions appear random or unpredictable, despite the consistent nature of their surroundings.

The other terms have specific meanings that do not convey this randomness. For instance, "pecking order" refers to a social hierarchy within a group of animals, typically establishing dominance and subordinate relationships. "Crepuscular" describes animals that are active during twilight hours, whereas "nocturnal" pertains to organisms that are active at night. Both of these terms indicate regular patterns based on light conditions rather than a lack of pattern.