Lesson Plan

• Describe how diffusion facilitates gas exchange and nutrient transport in organisms.
• Explain the factors that affect the rate of diffusion.
• Analyse real‑life examples of diffusion in respiratory surfaces and cellular transport.
• Predict the impact of impaired diffusion on organism health.
• Apply knowledge of diffusion to evaluate adaptations that enhance exchange.

• Projector or interactive whiteboard
• PowerPoint slides covering diffusion concepts
• Diagram handouts of an alveolus and leaf stomata
• Worksheet with Fick’s law calculations and scenario questions
• Model of a lung/alveolar membrane (optional)
• Markers and chart paper for group activity

Begin with a short video of bubbles rising in water to spark curiosity about how substances move without energy. Ask students what they already know about gas exchange in lungs and leaves, linking to prior lessons on cell membranes. State that by the end of the lesson they will be able to describe diffusion, its controlling factors, and why it is vital for life.

1. Do‑now (5'): Quick quiz on concentration gradients and equilibrium.
2. Mini‑lecture with slides (10'): Define diffusion, introduce Fick’s first law, and list factors influencing rate.
3. Demonstration (8'): Diffusion of food colouring in water to illustrate surface area and distance effects.
4. Guided analysis (12'): Examine alveolus diagram, label structures, and discuss O₂/CO₂ exchange.
5. Group worksheet activity (10'): Scenarios on impaired diffusion and adaptations that enhance it.
6. Check for understanding (5'): Exit ticket – write the single factor they consider most important for diffusion speed.

Summarise that diffusion is a passive, energy‑free process essential for gas exchange, nutrient uptake, waste removal and osmoregulation. Collect exit tickets and highlight common correct answers. For homework, ask students to research one animal or plant adaptation that improves diffusion and prepare a brief poster.