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How life began on the earth


Unit 4

Astronomy: the science of the stars

What is Astronomy? Astronomy is the scientific study of the universe and the heaven bodies (such as the sun, the moon, and st

ars, gas, and dust within it).

What do you know about the universe?

Scientists now think Pluto is too small to be called a planet.

We live on the same planet — the earth

1. Do you know the origin of life on the earth? 2. Each religion or culture has its own ideas about how life began on earth.

In Chinese culture…

sky

earth Pangu 盘古 separates(分) the sky ____________ from the earth.

_____________ Nuwa (女娲) made human beings.

In western countries:
God (上帝) ______________ created

the world and all living things.

Pre-reading

Do you know what a scientific idea is?
Background knowledge The Big Bang is the term used to describe a huge explosion that scientists believe happened about 15 billions years ago. Nobody knows what caused the Big Bang. But it was the event that created our universe.

The Big Bang

The universe began with a Big Bang.

Reading: How Life Began on the Earth
Read the title and look at the pictures, Predict what the reding will be about.

The evolution/development of life on the earth.

What is the writing style of this text?
A. narration(记叙文) B. exposition(说明文) C. argumentation (议论文) D. practical wrting(应用文) In what order is the text developed?
It is developed in time order.

( 1 ) Fast Reading

How life began on the earth
Read the passage on P25 quickly, and conclude the main idea of each paragraph.

1. No one knows exactly how the earth began, as it happened so long ago.However However, according to a widely accepted theory, the universe began with a "Big Bang" that threw matter in all directions. After that, atoms began to form and combine to create stars and other bodies.

Main idea: A widely accepted theory about the formation of the universe.

2. For several billion years after the "Big Bang", the the earth the earth earth was still just a cloud of dust. What it was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe. The earth became so violent that it was not clear whether the earth the shape would last or the not.earth It exploded loudly with fire and rock. They were in time to produce carbon, nitrogen, water vapour and other gases, which were to make the the earth's earth's atmosphere. What is even more important is that as the earth cooled down, water began to appear on its surface. the earth's

Main idea: The formation of the earth.

3.water Water had also appeared on other planets like water Mars but, unlike the earth, it had disappeared later. It was not immediately obvious that water water was to be fundamental to the development of life. What many scientists believe is that the continued presence of water water allowed the earth to dissolve harmful gases and acids into the oceans and seas. This produced a chain reaction, which made it possible for life to develop.

Main idea: The importance of water for life.

4. Many millions of years later, the first extremely small plants plants began to appear on the surface of the water. They multiplied and filled the oceans and seas with oxygen, which encouraged the later development of early shellfish and all sorts of fish. Next, green plants began to grow on land. They were followed in time by land animals animals. Some were insects. Others, called amphibians, were able to live on land as well as in the water. Later when the plants grew into forests, reptiles appeared for the first time. They produced young Main idea: The eggs. development of plants and generally by laying After that, some huge animals, called dinosaurs, developed. They laid eggs too and animals on the earth. existed on the earth for more than 140 million years. However, 65 million years ago the age of the dinosaurs ended. Why they suddenly disappeared still remains a mystery. This disappearance made possible the rise of mammals on the earth. These animals were different from all life forms in the past, because they gave birth to young baby animals and produced milk to feed them.

5. Finally about 2.6 million years ago some small clever cleveranimals animals, now with hands and feet, appeared and spread all over the earth. Thus they have, in their turn, become the most important animals on the planet. But they are not looking after the earth very well. They are putting too much carbon dioxide into the atmosphere, which prevents heat from escaping from the earth into space. As a result of this, many scientists believe the earth may become too hot to live on. So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved.

Main idea:The arrival of humans and their impact on the earth.

Passage structure
A widely accepted theory about the Para 1: formation of the universe.

Main body

Para 2: The formation of the earth. Para 3: life The importance of water for life. development Para 4: The development of plants and animals on the earth. The arrival of humans and their Para 5: impact on the earth.

( 2 ) Detailed Reading

Part 2: The development of life on the earth.

Para.2 The formation of the earth.

How did the earth come into being? (1) After the Big Bang, what happened? (2) What happened to the solid globe next? (3) What did the water vapour and gases were to make? (4) What appeared after the earth cooled down?

(1) After the Big Bang, what happened?

a cloud of dust

Settled into

a solid ball

(2) What happened to the solid globe next?

exploded with In time produced water vapour and gases fire and rock

(3) What did the water vapour and gases were to make?

the earth’s atmosphere

(4) What appeared after the earth cooled down?

Water appeared on its surface which is important for the beginning of life on the earth.

Retell the formation of the earth
Big Bang a solid _______ ball/globe

dust a cloud of _____

fire and _____ rock it exploded loudly with _____
the earth ’s atmosphere ___________

cooled down the earth ______

water

Para.3 The importance of water for life.

What did the water do?

3. Water had also appeared on other planets like Mars but, unlike the earth, it had disappeared later. It was not immediately obvious that water was to be befundamental fundamentalto tothe development of life. What many scientists believe is that the continued presence of water allowed the earth to dissolve harmful gases and acids into the oceans and seas. This produced a chain reaction, which made it possible for life to develop.

Para.4 The development of plants and animals on the earth.

Make a timeline of the development of life

Many millions of years later, the first extremely small plants began to appear on the surface of the water. They multiplied and filled the oceans and seas with oxygen, which encouraged the later development of early shellfish and all sorts of fish. Next, green plants began to grow on land. They were followed in time by land animals. Some were insects. Others, called amphibians, were able to live on land as well as in the water. Later when the plants grew into forests, reptiles appeared for the first time. They produced young generally by laying eggs. After that, some huge animals, called dinosaurs, developed. They laid eggs too and existed on the earth for more than 140 million years. However, 65 million years ago the age of the dinosaurs ended. Why they suddenly disappeared still remains a mystery. This disappearance made possible the rise of mammals on the earth. These animals were different from all life forms in the past, because they gave birth to young baby animals and produced milk to feed them.

Para.5 The arrival of humans and their impact on the earth.

clever animals with hands and feet

5. Finally about 2.6 million years ago some small clever animals, now with hands and feet, appeared and spread all over the earth. Thus they have, in their turn, become the most important animals on the planet. But they are not looking after the earth very well. They are putting too much carbon dioxide into the atmosphere, which prevents heat from escaping from the earth into space. As a result of this, many scientists believe the earth may become too hot to live on.Why? So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved.
What impact do humans have on the earth?

The earth is getting warmer each year.
What effects will this have? How to solve this problem?

Suggested Answers: The earth will be so hot that no life will exist(存在)on the earth any more. To solve this problem, people should protect the earth carefully. They must stop putting too much carbon dioxide into the air , reduce pollution, control the population and so on .

We only have one earth. Without other livings, we human cannot live.

Homework
Write a summary of the development of life on the earth with the help of the statements in Ex2, using proper discourse markers and sentence connectors.


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