Assessing students' systems reasoning in ecology

In this study, several assessment rubrics were used to analyse students' systems reasoning about food web perturbations and pollutant effects within ecosystems. An analytic paper/pencil task and a constructive interview task prompted the reasoning of two classes of 11 year old students (n = 52), before and after they participated in a month-long, hands-on unit in which they constructed, observed, and manipulated mini-ecosystems. When analysing population dynamics in response to perturbations within a food web students used predominately one-way linear, rather than more sophisticated two-way and cyclic reasoning, both before and after the instructional unit. They thus had limited models of patterns of relationships and reciprocal effects in ecosystems. When tracing how three different pollutants travel through and affect an ecosystem, 10 out of 16 focal students noted only effects that occur when pollutants come into direct contact with organisms, rather than indirect impacts on organisms. These results point to limitations in awareness of patterns of systems interactions, and naive or missing domain-specific knowledge, as constraining students' systems reasoning in ecology.