Lesson Summary: In this lesson, students used the Claim, Evidence, and Reasoning (CER) framework to tackle the question, "If microorganisms are around us all the time, why aren’t we sick all the time?" Students began by exploring background information on microorganisms, including the immune system’s role in protecting the body and examples of how beneficial microbes coexist with humans. Using videos, readings, and class discussions, they gathered evidence to support their ideas. Students then formulated a claim addressing the question, cited evidence such as the role of good bacteria or immune responses, and provided reasoning that connected their evidence to the claim. After completing their CER responses, students shared and discussed their ideas in small groups, refining their arguments based on peer feedback. This lesson encouraged critical thinking and real-world application of scientific concepts, helping students understand the complex relationship between humans and microorganisms.