The "Needs of Seeds" formative assessment probe can be used to find out whether students recognize that seeds have needs both similar to and different from plants and other living organisms (Keeley, Eberle, and Tugel 2007). The probe reveals whether students overgeneralize the needs of seeds by assuming they have the same needs as the adult plants that grow and develop from a seed during the life cycle of the plant. Through a process of elicitation, exploring, and testing their ideas about seeds, engaging in argumentation and sense making, and reflecting back on their initial thinking, "Needs of Seeds" provides an assessment springboard for students to learn about the needs of living things, hone their skills of inquiry, and experience the nature of science. In addition, teachers can gather valuable formative assessment information about their students' thinking and their ability to identify the evidence they need to support their ideas. (Contains 2 figures.)