In the present study, we have applied a word association procedure for assessing conceptual change in science education, leaning on the presuppositions of the theory of social representations. The proposed method was applied both before and after a university population ecology course. Our results have shown that the teaching procedure can change representations of stimulus terms, which could be considered analogous to "strong restructuring." The methodology proved to be quite efficient in monitoring stimulus terms' extentness, as well as associations' centrality, validity, and coherence. The easiness of collecting data, as well as the potential of conducting rather unbiased longitudinal studies can contribute to the attractiveness of the methodology.