The purpose of this assessment probe is to elicit students’ ideas about decay and decomposers. It can be used to determine whether students recognize the need for a biological agent to break down once-living material as it uses it for energy. Elementary students build an understanding of biological concepts through directly observing phenomena, such as the rotting apple. Middle school students become familiar with the beneficial role of bacteria in ecosystems. They expand their understanding of decomposers and decay to include microorganisms and recognize their essential role in the decomposition process as matter recyclers. High school students approach decomposition from a molecular view, including the assortment of complex biological processes involved in breaking down once-living material. Teacher notes, standards, assessment, and references are provided. This book selection also includes the Table of Contents, Dedication, Preface, Introduction, and Index..