Unit 3 Animals Are Our Friends.Lesson 17 Save the Tigers.教学课件

课件14张PPT。Lesson 17 Save the TigersNew wordsStructures and Expressionsat the beginning of… 在……之初drop to 下降到；跌至food chain 食物链in balance 保持平衡in danger 处于危险状态cut down 把……砍倒；减少as well （除某事或某人外）还；也Where can you usually see a tiger?Think About It2.Do you think tigers need our help?How many tigers was there at the beginning of 20th century？
Read and Answer:世纪的表达：
century的复数为centuries。当表示第几世纪，要用序数词前加定冠词the
*This book was written _____ (century) ago。
The telephone was invented in _____(a/an/the)19th century.centuriesthethe number of 和a number of的区别the number of表示......的数量后接可数名词的复数形式，作主语时，谓语动词用单数。
The number of the students in our school ____(be) about 3500.
a number of为许多、大量，作主语时，谓语动词用复数。
A number of students ___(be) playing in the playground.are isa few thousand 几千
thousands of 数以千计的
当hundred, thousand 前面是基数词one, two, three…, a few, many 时，其后不加s.
当hundred, thousand 后面加s时，需要跟of修饰可数名词复数。
Eg: There are three thousand students in our school.
Thousands of students are on the square.Read and Answer:
Where do tigers live in?
food chainbe important to sb./sth.
·······对于·······来说是重要的
be important for sb. to do sth.
做某事对某人来说是重要的Eg : Time is important to me.
时间对我来说很重要
It is important for you to learn
English well.
对你来说学好英语很重要Read and Answer:
Why do some people hunt and kill tigers?in danger（ of） 处于(······)危险之中，of后
接名词 或V-ingEg: The sick man is in danger of death.
这个病人有死亡的危险。 n.
You’re in danger of catching a cold.
你有患感冒的危险。 V-ing
The little boy is in danger! Let’s go
and help!
这个小男孩有危险！让我们去帮忙吧！
as well 位于句首或句末，在局末尾时，
不用逗号分开。用于肯定句。
too 位于句末，前面用逗号分开。
用于肯定句。
either 位于句尾，其前有无逗号均可。
用于否定句。
also 位于be动词和助动词之后，
行为动词之前，用于肯定句。表示“也”的短语和单词