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    The effect of light intensity on rate of photosynthesis in pondweed: plan

    I can plan an investigation into the effect of light intensity on the rate of photosynthesis in pondweed.

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    New

      The effect of light intensity on rate of photosynthesis in pondweed: plan

      I can plan an investigation into the effect of light intensity on the rate of photosynthesis in pondweed.

      Lesson details

      Key learning points

      1. Pondweed is a plant that photosynthesises in the light, releasing oxygen gas as a waste product.
      2. Planning an investigation into the effect of light intensity on the rate of photosynthesis in pondweed.
      3. Identifying the independent variable (light intensity) and planning how to vary it.
      4. Identifying factors that should be controlled and how they could be controlled (e.g. temperature).
      5. Planning methods to measure the dependent variable (number of bubbles and volume of gas given off).

      Keywords

      • Rate - a measure of how much change occurs per unit of time

      • Light intensity - the amount of light reaching a given surface area in a period of time

      • Hypothesis - an idea, for example an idea about an outcome of an experiment, based on observations and understanding

      • Variable - a factor that can be changed during an experiment

      • Control variable - a factor that is kept the same during an experiment

      Common misconception

      Some pupils do not consider how to control variables carefully enough. This means results are likely to be less accurate and so do not provide conclusions that can be used to support a hypothesis.

      Each type of variable is considered during the lesson and repeated to help pupils to understand the differences between each type of variable.

      Use real practical equipment to provide pupils to think about the types of equipment that can be used and to help pupils analyse risk effectively. Ask pupils to handle the equipment and consider how they might use it, so they can approach the tasks with workable ideas.
      Teacher tip

      Equipment

      Licence

      This content is © Oak National Academy Limited (2026), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

      Download quiz pdf

      6 Questions

      Q1.
      What is the basic purpose of photosynthesis in plants?

      to absorb nutrients from the soil
      to produce carbon dioxide and water
      Correct answer: to produce glucose and oxygen
      to store sunlight

      Q2.
      Where in the plant cell does photosynthesis occur?

      Correct answer: in the chloroplasts
      in the mitochondria
      in the nucleus
      in the cytoplasm

      Q3.
      What is an independent variable in an experiment?

      a factor that cannot be measured
      Correct answer: a factor that is changed during an experiment
      a factor that is kept the same
      a factor that doesn’t affect the results of the experiment

      Q4.
      Which type of variable is kept the same during an experiment?

      independent
      dependent
      Correct answer: control

      Q5.
      What is measured as the dependent variable in this photosynthesis experiment?

      An image in a quiz
      amount of light absorbed by the plant
      Correct answer: number of bubbles and volume of gas given off
      temperature of the water
      the mass of the plant before and after the experiment

      Q6.
      What safety measures should be considered when handling experimental apparatus?

      Ignore safety guidelines.
      Use equipment without checking it first.
      Correct answer: Wear safety goggles and handle equipment carefully.
      Correct answer: Ensure all equipment is correctly set up before use.

      Assessment exit quiz

      Download quiz pdf

      6 Questions

      Q1.
      What is the main product of photosynthesis?

      carbon dioxide
      Correct answer: glucose
      water
      light

      Q2.
      Which part of the plant cell captures light for photosynthesis?

      cell membrane
      mitochondria
      nucleus
      Correct answer: chloroplasts

      Q3.
      What is the independent variable in an experiment investigating the effect of light intensity on the rate of photosynthesis?

      carbon dioxide concentration
      Correct answer: light intensity
      temperature
      type of plant

      Q4.
      Which of the following is an example of a control variable in a light intensity experiment?

      Correct answer: distance of the plant from the lamp
      type of plant
      number of oxygen bubbles produced
      change of colour of universal indicator

      Q5.
      How can the distance of the plant from the lamp be controlled in the experiment?

      Correct answer: by using a ruler to measure the distance
      Correct answer: by marking a fixed position for the lamp
      Correct answer: by placing the plant on a stand at a set height
      by trying to keep the plant and lamp in the same position throughout

      Q6.
      What would be plotted on the x-axis in a graph of light intensity and photosynthesis rate?

      rate of photosynthesis
      Correct answer: light intensity
      temperature of the water
      carbon dioxide concentration

      Lesson appears in

      UnitBiology / Photosynthesis: factors affecting the rate

      AQABiology

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      OCRBiology

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      UnitCombined science / Photosynthesis: factors affecting the rate

      AQACombined science

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      OCRCombined science

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