We have developed an experimental module that introduces high school students to guided scientific inquiry. It is designed to incorporate environmental health and ecological concepts into the basic biology or environmental-science content of the high school curriculum. Using the red worm, a familiar live species that is amenable to classroom experimentation, students learn how environmental agents affect the animal's locomotion by altering sensory neuron-muscle interactions and, as a result, influence its distribution in nature. In turn, the results of these experiments have direct application to human-caused environmental disruptions that cause changes in species distribution and indirectly increase the recognition that environmental chemicals affect human health. Students undertake a series of explorations to identify how red worms sense their environment and then apply that knowledge to understand the effects of chemical exposure on locomotor behavior. The activities are designed to generate critical thinking about neuromuscular processes and environmental pollutants that affect them.