Which organ system is primarily involved in sensing environmental changes in insects?

The nervous system is primarily responsible for sensing environmental changes in insects. This system allows insects to detect stimuli from their surroundings, such as light, sound, temperature, and chemical signals, through specialized sensory organs. These sensory inputs are then processed by the nervous system, enabling insects to respond accordingly to their environment, which is crucial for their survival, navigation, feeding, and avoiding predators.

Unlike the circulatory, respiratory, or digestive systems, which have specialized functions of transporting nutrients and gases or breaking down food, the nervous system specifically focuses on perception and reaction to environmental factors. Thus, it plays a critical role in an insect's ability to adapt to changes in its habitat and respond to threats or opportunities.