Final answer:
The term for when an organism slows down its body systems during cold temperatures is hibernation, a state of torpor allowing survival by conserving energy and resources.
Step-by-step explanation:
The term for when an organism slows its body systems during periods of cold temperatures is hibernation. Hibernation is a state of torpor that occurs typically over the winter months, allowing animals to survive cold conditions by significantly lowering their metabolic rate. This process helps them conserve energy when food is scarce. Animals, such as bats, squirrels, and snakes, are known to hibernate. In contrast, estivation is another form of torpor that occurs during hot, dry periods, such as summer in desert regions.