This Concept Introduction / Review Activity directly supports NGSS Standard MS.LS4.6: Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time. The purpose of this 45 minute, 5E investigation is to explain how natural selection affects populations over generations by influencing which traits become more or less common. Students will read passages about natural selection and mathematical representations in tracking trait changes over time. Students will answer structured questions to analyze how traits shift in populations due to environmental pressures. Varied instructional grouping and activities can be applied to this foundational concept introduction and review activity. This package includes a lesson plan, instructor activity guide, students activity guide, response worksheet, answer key, and digital response worksheet. Just print, prep, and it’s ready to go.