Page 12 - 新思维科学学生用书9 样章

1.1 Photosynthesis

Activity 1.1.2

Photosynthesis and respiration
In Stage 8, you learnt about respiration.

Think about each of these questions on your own. Then turn and discuss them with
your partner.
• What similarities are there between photosynthesis and respiration?
• What differences are there between photosynthesis and respiration?

Now share your ideas with the rest of the class.

Why is photosynthesis important?

First, photosynthesis provides energy, in the form of chemical energy in nutrients, for most other
organisms.

Plants use the energy in sunlight to make glucose. From glucose other carbohydrates are made. These
carbohydrates contain some of the energy that was originally in the sunlight.

Think about what you have learnt about food chains. When animals eat food, they get some of the
energy that was captured by plants. Most of the energy in all the food in the world comes from plants.

A food chain shows us how this energy is passed along from one organism to another.

The second reason that photosynthesis is so important is that it provides oxygen for the Earth’s
atmosphere. Animals and plants, of course, need oxygen for respiration.

Oxygen is a waste product of photosynthesis. It is released from the leaves of plants and mixes with the
other gases in the atmosphere. About 20% of the air around us is oxygen.

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