This paper reports on a study of ecology teaching and learning in a Swedish primary school class (age 10-11 yrs). A teaching sequence was designed to help students read nature in a river ecosystem. The teaching sequence had a 'bottom up' approach, taking as its starting point a common key organism - the freshwater shrimp. From this species and its ecology, the perspective was broadened to involve studies of the interrelations between organisms and finally to the relationship between biotic and abiotic factors. A large part of the instruction took place outdoors. Students were interviewed three times during the course when they were presented with a tray full of objects (both biotic and abiotic) from the ecosystem. The students' task was to name and describe the objects and then to link them up in as many relevant ways as possible, explaining the reasons for the links. The interviews have been transcribed onto concept maps and SOLO-taxonomy was used to illustrate their developing ecological understanding. Results indicate how students related several abstract processes and correlations back to the key organism studied early in the teaching sequence.