必修3unit4 how life began on the earth

Unit 4 Astronomy

the science of the stars授课人：何艳双

Match the main idea with each paragraphPara.1 Para.2A.The importance of water for life B.A theory about how the universe was formed

Para.3Para.4 Para.5

C.The formation(形成) of the earthD.The arrival of humans and their effects on the earth E.The development of plants and animals

Para.1

a widely accepted theory

1.what is the widely accepted theory? The universe began with a “Big Bang”. 2.How did the Big Bang create the universe? First of all , threw matter in all directions it _____ _________. After that , atoms began to ________. form Then, atoms combined to create _____and stars ___________ other bodies .

Para.2

The formation(形成) of the earth

How did the earth form?

Para.2

The formation(形成) of the earth 1 settled into 2

a cloud of dust

A solid globeexploded with fire and rock cooled down

4

3

water

atmosphere:

carbon,

nitrogen, water and other gases

Para.3

The importance of water for life

1.What makes the earth different from the other planets? A. It produced a lot of heat. B. The continued presence of water C. Water disappeared. D. It was the oldest planet. 2.What’s the importance of the presence of water on the earth? Water allowed the earth to dissolve __________ harmful gases and acids into the oceans and seas, producing a_______________. chain reaction

Para.4Put the following into the right orderA. Insects and amphibians appeared

B. Dinosaurs appeared.C. Small plants grew on the water.

D. Reptiles appeared.E. Shellfish and other fish appeared. F. Plants began to grow on dry land. G. Mammals appeared. C E F A D

B

G

Para.5 The arrival of humans and theireffects on the earthFind out a sentence in this paragraph to describe the picture:CO2

They are putting too much carbon dioxide into the atmosphere, which prevents heat from escaping from the earth into space.

As a result, the earth may become too hot to live on .

Fill in the blanks with the proper words:The universe began with a________. “Big Bang” After that, the earth was a cloud of ____.Later, it dust settled into a solid ____. globe It ________ exploded loudly with fire and rock .They were in ____ time to produce many things, which were to make the earth’s atmosphere. As the earth cooled down, _____ appeared. Then life began to develop. water

The small plants___________ mulitplied and filled the oceans and seas with oxygen.This encouraged development of early shellfish and all the ____________ sorts of fish. Later, land animals appeared. Small clever animals spread all over the world. They are putting too_______carbon much dioxide into the atmosphere, which_______ prevents heat from escaping the earth into space. Whether Whetherlife lifewill willcontinue continueon onthe theearth earthfor for millions ______ millionsof ofyears yearsto tocome comewill willdepend dependon on whether whetherthis thisproblem problemcan canbe besolved. solved.

Di

scussionWhat can we do to take care of the earth?solar energy plant … recycle rubbish prevent the fields from becoming…make the air…

save …

We have only one earth!We should take care of the earth!

Homework1. Read the passage again after class and retell it. 2. Write a composition about how to protect our earth.