◎英國(guó)大使館文化教育處

Read a conversation between a biology student and his friend.

So,Simon,you’re studying biology.Can you explain a little bit about it?

Biology is about all the things on our world that are alive—plants,animals,as well as very small living things that we cannot see.Biology tries to explain why life is like it is.

It sounds complicated.There are so many different kinds of plants and animals.

That’s true.Different kinds of plants and animals can look very different.But they usually keep alive in the same way.For example,nearly all plants photosynthesize.This is how they get their energy.If we understand photosynthesis,then it makes things a lot more simple.

Photosynthesis.I remember studying this at school.I don’t think I understand it very well.

Well,I will try and explain.Plants take light from the sun,as well as water from rain and rivers,and carbon dioxide from the air.Carbon dioxide is a type of gas that people and animals make when they breathe.Inside the green parts of each plant is something called“chlorophyll”.This helps the plant to make sugar using light,water and carbon dioxide.Then the plant uses the sugar to make energy,so it can grow.

Why is it so important?

Before photosynthesis,there were no plants,flowers,trees,animals or people—just an empty world with only very small living things that we cannot see.

Did it help animals and people then?

Yes,by making oxygen.Oxygen is the gas that keeps you and me and every other human alive.We breathe in oxygen and it keeps our hearts going.But it is photosynthesis that makes oxygen.

Oxygen? You didn’t say oxygen earlier.

That’s because it is not used by plants.It is made by them during photosynthesis but they don’t need it.We do.

Wow.That’s lucky.Thanks,plants!

Activity 1 Complete the sentences.

Look at the following “word family”.These words have the same meanings but their grammar is different.

a.alive b.live c.life

Complete each sentence below using one of these words.

1.People who eat healthy food _____ for a long time.

2.She had a very bad accident.It’s very lucky she’s still _____.

3.He died when he was 96 years old.He had a long and interesting _____.

Activity 2 Look at the words below (a–d) and complete the sentences(1–4).

a.complicated b.breathe c.energy d.light

1.If something is _____,it is difficult to understand.

2.Do exercise,you need _____.

3.When you _____,you take air into your body.

4.The sun makes the world warm and gives it _____.

Activity 3 Complete the sentences below using the words in the list (a–e).

a.humans b.breathe c.oxygen d.light e.energy

Photosynthesis is one of the most important things that happen in the world.Plants use 1._____,water and carbon dioxide to make sugar.This sugar then gives them the 2._____ they need to grow.Photosynthesis is also important for 3._____.Because it makes 4._____,which we need to 5._____.Without photosynthesis,humans and animals cannot live.