Target Grades:Middle School and High School (modification suggestions for each level are included).
Description: The activities in this unit engage students in collecting data about plant growth and gas exchange, then in developing a scientific explanation for their observations. A major focus of the unit is to engage students in the question of where the dry plant matter came from (i.e., not from the soil or water, but from the air), and what plant matter is (it is based on carbon). These activities will lay a foundation for tracing carbon through organisms and ecosystems, improving student understanding of the global carbon cycle.
Learning Goals: This unit is designed to help students make the connections described above by engaging them in two kinds of practices:
- Inquiry or investigating practices, in which students learn to:
- Make careful measurements of plants’ dry weight or biomass and gas exchange (absorbing and releasing carbon dioxide) in light and dark conditions, and
- Construct arguments from evidence about how plants grow and exchange gases with their environment, and how growth and gas exchange are related.
- Accounts or explaining and predicting practices. This unit addresses five different aspects of explaining and predicting plants’ growth and gas exchange. Two are core goals of this unit. They are:
- Identifying reactants and products of the key carbon-transforming
- Processes in plants: photosynthesis, biosynthesis, and cellular respiration.
- Explaining photosynthesis, biosynthesis, and cellular respiration using atomic-molecular theory
- Explaining energy transformations in photosynthesis, biosynthesis, and cellular respiration
- Locating photosynthesis, biosynthesis, and cellular respiration in the general carbon cycle
Lesson Plans: These documents contain teacher instructions and student worksheets for all of the lessons in this unit.
Teacher guide(download: PDF)
Student Activities (download: PDF)
Student Readings (download: PDF)
Additional Support Materials for Lessons:
Powers of 10 Poster (download) – Chart containing notations for spatial scales from 10^-10 to 10^5 meters, with areas for the four ‘benchmark’ scales (atomic-molecular, microscopic, macroscopic and large-scale) color-coded. This simple tool can be used to discuss the relative sizes of nearly any object that you might discuss in your courses, even outside of this unit.
Lesson 2: Powers of 10 (General) (download) – Presentation which moves students from the scale of the whole earth to a single carbon atom.
Lesson 3: Powers of 10 (Animated answers) (download)– Single slide with animation that brings in all of the powers of 10 cards in this lesson to their proper places on the chart (i.e.- an answer key).
Lesson 4: Powers of 10 (Air) (download) and Powers of 10 (Plant) (download) – Slideshows which move students through a subset of the powers of 10 to focus more directly on the structure of both air and plants. This introduction can then help students to make sense of the explanations that their observations in the upcoming activities will be pointing them towards. (Note: this animation–air molecule movement (download) is necessary for the final slide on the ‘air’ slideshow to work correctly.)
Lesson 5: Weight Gain and Loss (download) – Slideshow which guides students through the process and rationale for tracing wet and dry biomass separately.
Lesson 7: Probe Difficulties (download) – Sample probe graphs
Lesson 8: Plants & Photosynthesis (download) and Plants & Respiration (download) – Slideshows which build off of the ‘plant’ slideshow used in Lesson 4 to focus students on the structures that allow plants to undergo photosynthesis and respiration. Both slideshows have an animation you will need to download (Photosynthesis Video (download), Cell Respiration Video (download)).
Lesson 9: Sample Data and Graphing Template (download) – Excel template for graphing class data, or comparing to sample data set.
Lessons 10: Matter Tracing Process Tool (download) – Slideshow for class discussions of photosynthesis, biosynthesis and respiration.
Lesson 11: CO2 Process Tool (download) – Slideshow including a simple terrestrial carbon cycle and atmospheric accumulation tool.