Year 8 Science · Unit 1 · Lesson 8

Gas Exchange in Plants

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Learning Goals

Warm Up

Because… chain

Fill in the missing effects. Each cause leads to the next step in the chain.

Gases (such as CO₂ and O₂) are present in the environment outside the plant
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The leaf surface interacts with the outside environment
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Gases move between the plant and its surroundings
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Cells use the exchanged gases for their processes (photosynthesis during the day; respiration at all times)
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Overall outcome for the plant:

Your Turn

Real-world context

Aquatic plants such as Elodea can be found in ponds and aquariums across Australia, including at the Sydney Aquarium. When light shines on these plants, tiny bubbles of gas can be seen rising from the leaf surfaces. When the light is turned off, bubble production stops. This shows that plant gas exchange is linked to whether light is available, a real, observable biological process that happens through the surface of the leaves.

(a) What gas do you think is being released in the bubbles when light shines on the plant? Use what you know from this lesson about plant gas exchange to explain your answer.

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(b) A student says: "The bubbles prove that plants breathe just like animals." Evaluate this claim, what is correct about it, and what is a more precise scientific way to describe what is happening?

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Show What You Know

1. Both plants and animals need to exchange gases with the environment. Describe one similarity and one difference in how they do this, using what you have learned about leaves (plants) and the respiratory system (animals).

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 8 Science · Unit 1 · Lesson 8 · Apply Worksheet