Lesson Plan

• Describe how light intensity, CO₂ concentration and temperature affect the rate of photosynthesis in whole plants.
• Design and conduct a controlled investigation that varies one factor while keeping others constant.
• Measure oxygen evolution accurately and calculate photosynthetic rates.
• Analyse data to identify the limiting factor and explain trends using enzyme‑kinetics concepts.

• Projector and screen
• Worksheet/record sheet for data collection
• Elodea sprigs (or spinach leaves)
• Transparent water bath with graduated cylinder (inverted)
• Variable‑intensity lamp and lux meter
• Thermometers
• CO₂ syringe or gas burette
• Safety goggles and lab coats

Begin with a quick video showing how plants capture light in different environments to spark curiosity. Ask students what they already know about factors that can speed up or slow down photosynthesis. Explain that today they will investigate three key variables and will be able to predict which factor limits the reaction under given conditions.

1. Starter – “Limiting Factors” brainstorming (5 min).
2. Mini‑lecture on photosynthetic rate measurement and variables (10 min).
3. Demonstration of the gas‑collection set‑up using Elodea (15 min).
4. Student investigations (choose one factor) – set up, collect O₂ data (30 min).
5. Data analysis – plot graphs, calculate rates, identify limiting factor (10 min).
6. Plenary – groups share findings; teacher highlights enzyme‑kinetics link (5 min).

Summarise how each variable influences the photosynthetic rate and why only one can be limiting at a time. Exit ticket: write the factor that limited your experiment and one real‑world example where that factor is critical. For homework, students draft a brief report describing their method, results and interpretation.