Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Biology
Lesson Topic: Investigate and describe the effects of variation of temperature, humidity and light intensity on transpiration rate.
Learning Objective/s:
  • Describe how temperature, humidity, and light intensity affect transpiration rate.
  • Explain the relationship between the water‑vapour pressure gradient and stomatal behaviour.
  • Analyse experimental data to determine the effect of each factor on transpiration.
  • Evaluate sources of error and suggest improvements to the experimental design.
Materials Needed:
  • Potometer (or graduated syringe) with airtight connections
  • Uniform pot plant (e.g., bean or pea)
  • Thermometer
  • Hygrometer or digital humidity sensor
  • Lux meter
  • Measuring cylinder and water source
  • Timer/stopwatch
  • Data collection worksheet
 Introduction:
Plants lose water through transpiration, a process that can be dramatically altered by their environment. Students already know that stomata regulate gas exchange and that temperature, humidity, and light influence plant physiology. By the end of the lesson they will be able to predict how each factor changes the transpiration rate and design a simple experiment to test it.
Lesson Structure:
  1. Do‑now (5') – Students answer a quick question on factors affecting transpiration on a worksheet.
  2. Mini‑lecture (10') – Review key concepts and introduce the quantitative relationship R = k·a(I)·ΔP using a projector.
  3. Demonstration (10') – Set up the potometer, show how to record baseline water level and read sensors.
  4. Group investigation (20') – Students conduct trials varying one factor (temperature, humidity, or light) while recording data on the worksheet.
  5. Data analysis (10') – Calculate transpiration rates, plot graphs, and discuss trends.
  6. Plenary (5') – Teacher summarises findings and addresses misconceptions.
Conclusion:
To consolidate learning, we revisited how each environmental variable modifies the water‑vapour pressure gradient and stomatal opening. For the exit ticket, students write one prediction about how an untested condition would affect transpiration. Homework: complete a short report interpreting their graphs and suggest one way to improve the experimental design.