This study investigates how lower elementary students used the technical terms in the context of ecology. We interviewed 44 students using several scenarios related to the ecosystem. We determined the general frequency of technical terms used from a preselected list commonly employed by scientists in their discourse about ecosystems. Then, we identified the contextualisation of the technical terms. The results showed three categories: "naming"--where the terms referred to an event or object without any appropriate scientific explanation, "partial explanation"--where the terms revealed a scientific idea mixed with other alternative conceptions, and complete "scientific explanation"--where the terms were used to completely convey the proper scientific idea. We discuss the practical implication of those results for teaching ecology.