Step 1.Greetings.

设计意图：让学生做好上课的准备。

Step 2. Think about it.

1. Would you like to be a biologist when you grow up? Why or why not?

2. What mysteries of nature do you know about?

设计意图：与学生进行一个简短的对话，进入本课主题。

Step 3. Show students the new words in this lesson.

设计意图：通过展示生词让学生为学习课文做好准备。

Step 4. Read the lesson and find out the phrases.

1.引起某人的注意 draw one’s attention                     
2.回到、返回     return to…
3.多达           as many as
4.下蛋           lay eggs
5.在大学里       at a university

6.小片的森林     small piece of forest

7.动身去某地     leave for sp.

设计意图：让学生带着任务读课文。

Step 5. Read the lesson again and finish the following questions.

1. In the United States and Mexico, farmers use chemicals that kill milkweed. (    )

2. Do the females lay eggs on only one plant?

________________________________.

3. What does Dr. Chip Taylor study? 

_______________________________________________.

4. Here, as many as ___________ butterflies spend the winter.

5. In Mexico, the butterflies always return to the same small piece of forest, which is only 20 kilometers wide.

Step 6. Language Points

1. attention

1)draw one’s attention to sth. (使某人注意某事).

2) catch one’s attention  (引起某人注意)

3) pay attention to sth.  (注意、留心)

4) give one’s attention to sth.  (关心)

2. as…as…

1) He is ___________ his father.(像…一样高)

2) I do my homework ___________ my sister does.(像…一样认真)

3) They see ___________ one hundred students in front of the library. (像…一样多)

3. lie 与 lay

1) lay (下蛋) --- laid --- laid --- laying