Teacher sheet · Ages 10–11 · about 45–50 minutes
Photosynthesis: how a plant makes food
Lesson page: echoesof.science/school/plants/ages-10-11/ · Pupil worksheet: echoesof.science/school/plants/ages-10-11/print/
Learning aims
- Write the word equation for photosynthesis.
- Explain the roles of chloroplasts, chlorophyll and stomata.
- Describe water transport through roots and xylem, driven by transpiration.
- Use a control in an investigation.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: a big tree weighs tonnes. Where did all that material come from? Collect guesses. |
| 10 min | Read the text; build the word equation on the board. |
| 15 min | Set up the coloured-water flowers. |
| 10 min | Game: Inputs and outputs, then the quiz. |
| Next day | Observe the flowers and cut the celery; complete the worksheet. |
Materials for the experiment
- A white carnation, white chrysanthemum or a stick of celery with leaves
- Two glasses of water
- Food colouring (blue or red works best)
- Scissors (adult only) or a table knife
- A magnifying glass
Safety: Only an adult uses scissors or knives. Food colouring stains clothes and hands: wear an apron and cover the table.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Most of a plant's mass comes from the soil. | Most comes from carbon dioxide in the air and water; the soil gives water and minerals. |
| Plants breathe in carbon dioxide and animals breathe in oxygen. | Plants also use oxygen for respiration, day and night; photosynthesis is a separate process that runs in the light. |
| Xylem and phloem are the same. | Xylem carries water up; phloem carries sugars to where they are needed. |
Worksheet answers
- carbon dioxide + water → glucose + oxygen (light energy needed).
- Roots take up water; it travels up the xylem; water evaporating from the leaves (transpiration) pulls more water up.
- The petals or leaves turned the colour of the water because it travelled up the xylem. The plain glass is the control: it shows the colour came from the dye.
- Leaf outline with veins, stomata as small openings, and chloroplasts drawn in the cells.
Quiz answers
- Which is the word equation for photosynthesis? carbon dioxide + water → glucose + oxygen. Light energy turns carbon dioxide and water into glucose and oxygen.[1]
- Where in the leaf cell does photosynthesis happen? In the chloroplasts. Chloroplasts hold the chlorophyll that traps light.[1]
- What are the tiny holes in a leaf called? Stomata. Stomata let carbon dioxide in and oxygen out.[1]
- Which tubes carry water up from the roots? Xylem. Xylem carries water; phloem carries sugar.[3]
- What pulls water up the stem? Water evaporating from the leaves. Transpiration from the leaves pulls water upward.[3]
- Why are animals called consumers? They depend on plants for food, directly or indirectly. Animals cannot photosynthesise, so they rely on producers.[2]
Going further
Put a clear plastic bag over a leafy branch of a potted plant in the sun for an afternoon. Where does the water inside the bag come from?
Sources used in this lesson
- [1] Biology 2e, 8.1 Overview of Photosynthesis (OpenStax, Rice University): reliability High
- [2] Concepts of Biology, 5.1 Overview of Photosynthesis (OpenStax, Rice University): reliability High
- [3] Biology 2e, 30.5 Transport of Water and Solutes in Plants (OpenStax, Rice University): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/plants/sources/
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