Philip Gibson - Our World

Contents

. Our world

2. How things started

3. From gas and dust to stars and planets

4. The young planet Earth

5. The changing Earth

6. Where did life start?

7. The first life

8. Early bacteria

9. Life in the seas

10. The first life on land

11. Creatures of both land and water

12. Reptiles

13. The first mammals

14. More and more mammals

15. The first birds

16. Charles Darwin

17. More and more changes

18. Stronger and more beautiful

1. Our world

N ew Words:

find / found (out)

been

planet

scientist

Earth

billion

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W hat do you know about our world? Do you know a lot, or do you only know a little? You know a lot about where you live, dont you? You know a lot about your house and the places near your house. You have found out a lot about those places.

B ut what about the bigger world in which you live? What about your planet? What do you know about planet Earth?

The Planet Earth

D o you know how old the Earth is? Do you know how long animals and plants have been on Earth? Do you know where the Earth came from?

N obody really knows where our planet came from. That is a very difficult question to answer. Scientists have studied this question for a long time. They have been trying to find the answer, but they have not really found it yet. Even scientists who have studied this question all their lives are not really sure where the Earth and the other planets came from.

H owever, scientists have found out a lot of other things about the Earth. One of the most interesting things they have found out is how old the Earth is. They have found out that our planet is very old. It is very, very old! The Earth has been here for a long, long time. It is about four billion years old!

D o you know how much a billion is? A billion is a really large number. It is much, much bigger than a million. A billion is 1,000 million. That makes our planet very, very old! It makes the Earth about 4,000 million years old!

F our billion years ago, there were no people on the Earth. There were no animals, no fish, no birds and no insects. There were not even any plants! There was just the young planet Earth with no life on it.

H owever, the planet has changed a lot in those 4 billion years. Our planet has changed into the Earth we know today. Our planet has changed into a place where there are millions of different kinds of life. Now, everywhere we look on planet Earth, we can find life.

S cientists think that the first life on Earth started about 3 billion years ago. That was when the Earth was already one billion years old. The scientists who study this question think that all life may have started many thousands of meters under the sea. They think that the first kinds of animal and plant life were very, very small. We would not be able to see those plants and animals just using our eyes.

L arger sea animals , like the fish we see in the worlds seas today, have been on Earth for about 600 million years. Animals and birds, like the ones we see today, have only been on Earth for about 150 million years.

P eople came long after that. Really, people have not lived on Earth for very long at all! People came long after all the other animals, birds, fish and insects. People like us have only been on the Earth for a few hundred thousand years.

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Lee and his mother are talking about where Lee has been today

L ee

Hello, Mom.

M om

Hello, Lee. Where have you been? I have been looking for you.

L ee

I have been at Toms house. I have been with Tom.

M om

And what have you been doing?

L ee

Weve been looking for insects.

M om

Looking for insects? Did you find any?