Good Learning Co.
SavannahYear 8
← Science
ScienceLife processes25 min★★ difficulty

Inside a leaf: stomata and the gas trade

A leaf is a solar panel with a breathing problem. It needs carbon dioxide from the air, but every opening that lets gas in also lets water vapour out.

Part of your national curriculum
  • Biology: material cycles and energy: Understand the role of leaf stomata in gas exchange in plants and the dependence of almost all life on Earth on the ability of photosynthetic organisms to use sunlight

Lesson overview

What you'll learn in this lesson

Understand the role of leaf stomata in gas exchange in plants and the dependence of almost all life on Earth on the ability of photosynthetic organisms to use sunlight

Key learning points

  • • The layers of a leaf
  • • Stomata: adjustable pores
  • • Why the rest of life depends on this

This lesson at a glance

  • 25 minutes
  • 16 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

stomataexchangeplantsdependencealmost

Scroll down — the lesson carries on below

Part 1 of 16 · Discover6%
1

Watch & discover

Part 1 of 16

Watch first

Inside a leaf: stomata and the gas trade

An English teaching video on this topic from iNewittAll. Watch it, then scroll down for the lesson.

In a nutshell

Understand the role of leaf stomata in gas exchange in plants and the dependence of almost all life on Earth on the ability of photosynthetic organisms to use sunlight

2

Learning cycle

Part 2 of 16

Learning cycle 1 of 2

Part 1 · The layers of a leaf

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 16

Learn

The layers of a leaf

Light passes through a thin waxy cuticle and a clear upper layer, then reaches the palisade cells packed with chloroplasts. Below them, spongy cells sit in a maze of air spaces so gases can reach every cell.

4

Explore the idea

Part 4 of 16

Learn

Stomata: adjustable pores

Most stomata are on the underside of the leaf. Each pore sits between two guard cells. When the guard cells swell with water they curve apart and the pore opens; when the plant is short of water they slacken and the pore closes, protecting the plant but pausing photosynthesis.

5

Quick check

Part 5 of 16

Quick check

Where are most stomata found?

6

Quick check

Part 6 of 16

Quick check

What opens and closes a stoma?

7

Reset break

Part 7 of 16

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
8

Learning cycle

Part 8 of 16

Learning cycle 2 of 2

Part 2 · Why the rest of life depends on this

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 16

Learn

Why the rest of life depends on this

Photosynthetic organisms — plants, algae and some bacteria — are the only large-scale route by which sunlight energy enters food chains. Almost every other organism, including us, eats that captured energy second-hand and breathes the oxygen released as a by-product.

10

Quick check

Part 10 of 16

Quick check

Which gas diffuses into the leaf for photosynthesis?

11

Quick check

Part 11 of 16

Quick check

Why do almost all food chains depend on photosynthesis?

12

Explore the idea

Part 12 of 16

Worked example

Worked example: explaining a wilting plant

A plant left unwatered on a hot windowsill grows slowly even though it has plenty of light. Explanation: water loss is high, so guard cells close the stomata to conserve water. With the pores closed, carbon dioxide cannot diffuse in, so the rate of photosynthesis falls and growth slows — light was never the limiting factor.

13

Challenge round

Part 13 of 16

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

14

Challenge round

Part 14 of 16

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

Most ____ are on the underside of the leaf.

Photosynthetic organisms — ____, algae and some bacteria — are the only large-scale route by which sunlight energy enters food chains.

____ every other organism, including us, eats that captured energy second-hand and breathes the oxygen released as a by-product.

15

Mastery quiz

Part 15 of 16

Marked quiz

End of lesson quiz: Inside a leaf: stomata and the gas trade

4 questions, marked with the reasoning shown. No timer.

  1. 1. Where are most stomata found?

  2. 2. What opens and closes a stoma?

  3. 3. Which gas diffuses into the leaf for photosynthesis?

  4. 4. Why do almost all food chains depend on photosynthesis?

16

Lesson round-up

Part 16 of 16

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 16 · Watch & discover

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    Understand the role of leaf stomata in gas exchange in plants and the dependence of almost all life on Earth on the ability of photosynthetic organisms to use sunlight

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