UNIT 5 Look into Science Lesson 28 The Stuudy of Living Things 课件2.ppt

1、Look into Science,Unit 5,Lesson 28 The Study of Living Things,Introduction,Content,1,2,3,Contents,Homework,Introduction,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?,Question,Do you know some types of butterflies? Can you tell us

2、 something about that?,Content,Dr.Chip Taylor teaches biology at a university in the United States.,He studies one kind of North American butterfly.,Just like a migrating bird, this butterfly travels about 4000 kilometers south in fall. Fantastic facts about the butterfly have been drawing Dr.Taylor

3、s attention.,In Mexico, the butterflies always return to the same small piece of forest, which is only 20 kilometers wide.,Here, as many as 230 million butterflies spend the winter. They can cover some trees almost completely.,The butterflies that return to the south are the great-great grandchild o

4、f the butterflies that left for the north.,When they begin to travel north in spring, the females lay eggs. They lay eggs on only one plant: milkweed.,But in Mexico, people cut down the trees that the butterflies need to rest on because they want more land for farming.,In the United States and Canad

5、a, farmers use chemicals that kill milkweed. This worries Dr.Taylor a lot.,Now things are improving. Mexico has begun to protect parts of its forests and encouraged farmers to use less chemicals.,Scientists still dont understand how the butterflies know when to fly south.,If they are even a few days

6、 late, they will freeze. And how do all the great-great grandchild find the same forest in Mexico every year? This is both puzzling and interesting for many scientists.,There are many mysteries yet to be discovered by those who interesting in science. Would you like to study biology?,I. Memory all the new words and expressions.,II. Finish the exercises on the textbook.,Work in class,I. Collect some information about m