Page 13 - 新思维科学学生用书9 样章

1 Photosynthesis and the carbon cycle

When the Earth was first formed, about 4.6 billion years ago, there was almost no oxygen in the Earth’s

atmosphere. Scientists think that oxygen first began to collect in the air when bacteria first began to
photosynthesise. (There were no plants at that time – they did not appear on Earth until about 500
million years ago.) If photosynthesis had never begun on Earth, then no animals would ever have been
able to live here.

Questions
3 The picture shows a lizard eating a grasshopper. Grasshoppers

eat grass.
Explain how the lizard relies on photosynthesis to provide

it with energy.
4 Explain one other reason (apart from food) why the lizard
would not be able to survive if there were no plants on
Earth.

Summary checklist

I can write the word equation for photosynthesis.
I can explain that photosynthesis is the way that plants make carbohydrates,
using energy from light.
I can explain why photosynthesis is important for most life on Earth.

I can collect results carefully, and record them in a chart that I design myself.
I can use my results to make a conclusion.

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