“Lab 5: Photosynthesis: Why Do Temperature and Light Intensity Affect the Rate of Photosynthesis in Plants?” is one of 27 lab investigations for the high school student from the book, Argument-Driven Inquiry in Biology: Lab Investigations for Grades 9-12. This application lab assumes a basic understanding of photosynthesis and can be used as part of a learning sequence in which students work to make sense of a real-world phenomenon related to photosynthesis. The lab asks students to design experiments, construct arguments, and develop conceptual models to answer the guiding question. “Checkout Questions” are provided to facilitate student reflection on what was learned. Students are assigned a short investigation report to finish processing their experience. Significant background information is provided for teachers and to a lesser degree in the student hand-out in the introduction. The standards addressed in the lesson are also included in the teacher’s notes. Teachers are encouraged to refer to the introductory chapters and appendices of the book for important background on the practice of argumentation and resources for classroom implementation. Student handouts are provided in the book, but a separate student laboratory manual is also available: https://www.nsta.org/store/product_detail.aspx?id=10.2505/9781681400143. Additional supporting resources are also available at http://www.argumentdriveninquiry.com/.