Build a Model of Photosynthesis (advanced)
Goal:
Students will build a physical or visual model to represent the process of photosynthesis and understand how oxygen was introduced to Earth's atmosphere by cyanobacteria.

Background
Over 2 billion years ago, tiny organisms called cyanobacteria began performing photosynthesis. This process uses sunlight, carbon dioxide (CO₂), and water (H₂O) to make food—and it releases oxygen (O₂) as a byproduct.

This oxygen built up in the atmosphere over time, changing the world forever! It caused a mass extinction of organisms that couldn’t survive in oxygen and allowed new, aerobic (oxygen-using) organisms to evolve.

Photosynthesis equation:
CO₂ + H₂O + sunlight → O₂ + glucose (sugar)

Instructions
Step 1: Create Model Parts
Make separate labeled parts for:

• Inputs:
  • Carbon dioxide (CO₂) – cutout of air bubble or gas cloud
  • Water (H₂O) – raindrop or wave shape
  • Sunlight – yellow sun or ray
• Outputs:
  • Oxygen (O₂) – bubble or air puff
  • Glucose – sugar cube or simple hexagon

Step 2: Arrange on a Poster or Table
Set up the “reactants” on the left, with arrows pointing toward a cyanobacteria cell or chloroplast in the center. On the right, arrange the “products” coming out with arrows.

Label it:
Photosynthesis: The Oxygen-Making Machine!

Step 3: Explain the Model
Ask students to describe:

• What goes in to the cyanobacteria (CO₂, H₂O, sunlight)
• What comes out (O₂ and glucose)
• Why this matters for Earth’s history

Discussion Questions

• Why do scientists say cyanobacteria changed the world?
• What would Earth be like if photosynthesis had never evolved?
• Why did the rise of oxygen cause some life to go extinct?
• What types of organisms benefited from the new oxygen-rich environment?

Wrap-Up 

• Point to each part of their model and explain it
• Make sure they can articulate:“Photosynthesis is important because…”