Young Children’s Thinking About Decomposition: Early Modeling Entrees to Complex Ideas in Science

Abstract

This study was part of a multi-year project on the development of elementary students’ modeling approaches to understanding the life sciences. Twenty-three first grade students conducted a series of coordinated observations and investigations on decomposition, a topic that is rarely addressed in the early grades. The instruction included in-class observations of different types of soil and soil profiling, visits to the school’s compost bin, structured observations of decaying organic matter of various kinds, study of organisms that live in the soil, and models of environmental conditions that affect rates of decomposition. Both before and after instruction, students completed a written performance assessment that asked them to reason about the process of decomposition. Additional information was gathered through one-on-one interviews with six focus students who represented variability of performance across the class. During instruction, researchers collected video of classroom activity, student science journal entries, and charts and illustrations produced by the teacher. After instruction, the first-grade students showed a more nuanced understanding of the composition and variability of soils, the role of visible organisms in decomposition, and environmental factors that influence rates of decomposition. Through a variety of representational devices, including drawings, narrative records, and physical models, students came to regard decomposition as a process, rather than simply as an end state that does not require explanation.

Appendix: Classroom Pre- and Post-written Assessment

Every year, in the autumn, all the leaves fall off of the trees to the ground below. You may have enjoyed raking the leaves into huge piles and jumping in them. Although you have only been around for 6 or 7 years, the leaves have been falling each of those years and many more. That’s a lot of leaves!! Why aren’t there mountains of leaves covering everything after all this time? In the space below, carefully explain what you think is happening so that a student in Mrs. Smith’s class would understand. Draw and label a picture to help you explain what is happening to the leaves.