Adaptations Topic

Choosing the right concepts

This science revision note aims to help your child

– identify the correct concepts

– proper scientific keywords to explain the concepts clearly.

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Jackie has two plants of the same species and size in different parts of her house. Plant X is in the open garden under the sun, while Plant Y is under a shelter. She noticed that Plant X has slightly smaller leaves, while Plant Y has slightly larger leaves.

Scienceshifu - Adaptations - Leaves of different sizes

Explain why Plant X has smaller leaves than Plant Y.

STEP 1 – Identify the concepts

What is the difference between the surroundings of the plants that can cause the plants to adapt differently?

What!

Do you mean the same plant species can have leaves of different sizes?

Yes! That is possible.

They need to adapt to survive!

Why does plant X have smaller leaves? Remember: Plant X is under the sun.

Is it because it receives too much sunlight?

That cannot be as the more sunlight Plant X receives, the faster the rate of photosynthesis to make more food.

So more sunlight is beneficial to Plant X.

Hmmm…what else could cause the leaves of Plant X to be smaller?

Recall your science knowledge:

Scienceshifu - Sweating on a hot day

When the sunlight is of high intensity, do you feel the surrounding air is warmer (or even too hot for our liking)?

We then start to sweat.

Aha! Sweating! Plants give off water vapour.

Eureka!

The correct concept is the higher temperature of the surroundings. Plants lose water vapour through the stomata faster!

Alright! We’ve found the correct concept to explain why plant X is smaller.

Now, let us identify the correct concept for Plant Y.

Why does plant Y have larger leaves? Remember: Plant Y is under the shelter.

Can I use the same concept (temperature of surroundings affects water vapour loss) to explain for plant Y?

We don’t recommend that. That answer does not make sense as Plant Y has larger leaves and will have more stomata. Plant Y will be losing as much water vapour as (if not more than) Plant X.

Hence, using the same concept to explain Plant Y does not answer the question.

Instead, we can revisit the concept of light intensity received by the plant.

Plant Y receives less sunlight than plant X as Plant Y is under a shelter.

Hence, the correct concept is with less light intensity, plant Y has larger leaves to increase the exposed surface area to take in more sunlight to photosynthesise faster and make more food.

Step 2 – put your answer together

Question: Explain why Plant X has smaller leaves than Plant Y.

Answer:

Since Plant X is under the sun, the temperature of the surroundings is higher. This increases the loss of water vapour through the stomata of the leaves. So, Plant X has smaller leaves so there are fewer stomata and this reduces the amount of water vapour lost through the stomata.

Since Plant Y is under the shelter with less sunlight, it has larger leaves to increase the surface area exposed to the sun. Plant Y can take in more sunlight for photosynthesis faster and make more food.

Note: You need to compare!

Common mistakes

Wrong answer: The sizes of the leaves are different because the difference in the amount of sunlight affects how well the leaves grow. With more sunlight, there is a greater rate of photosynthesis, increasing the size of the leaves.

Teachers’ comments: This answer is not complete because the question tells you that Plant X is under the sun while Plant Y is under the shelter. Hence Plant X receives more sunlight. However, the question also tells you that Plant X has smaller leaves while Plant Y has larger leaves. We need to apply another concept to explain the difference.

Learning points