Unit 1

　　Part Ⅱ Reading Comprehension (Skimming and Scanning)

　　(15 minutes)

　　Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet1.

　　For questions 14, mark

　　Y (for YES) if the statement agrees with the information given in the passage;

　　N (for NO) if the statement contradicts the information given in the passage;

　　NG (for NOT GIVEN) if the information is not given in the passage.

　　For questions 5-10, complete the sentences with the information given in the passage.

　　Rainforests

　　Tropical rainforests are the most diverse ecosystem(生態(tài)系統(tǒng))on Earth, and also the oldest. Today, tropical rainforests cover only 6 percent of the Earth's ground surface, but they are home to over half of the planet's plant and animal species.

　　What Is a Rainforest?

　　Generally speaking, a rainforest is an environment that receives high rainfall and is dominated by tall trees. A wide range of ecosystems fall into this category, of course. But most of the time when people talk about rainforests, they mean the tropical rainforests located near the equator.

　　These forests receive between 160 and 400 inches of rain per year. The total annual rainfall is spread pretty evenly throughout the year, and the temperature rarely dips below 60 degrees Fahrenheit.

　　This steady climate is due to the position of rainforests on the globe. Because of the orientation of the Earth's axis, the Northern and Southern hemispheres each spend part of the year tilted away from the sun. Since rainforests are at the middle of the globe, located near the equator, they are not especially affected by this change. They receive nearly the same amount of sunlight, and therefore heat, all year. Consequently, the weather in these regions remains fairly constant.

　　The consistently wet, warm weather and ample sunlight give plant life everything it needs to thrive. Trees have the resources to grow to tremendous heights. and they live for hundreds, even thousands, of years. These giants, which reach 60 to 150 ft in the air, form the basic structure of the rainforest. Their top branches spread wide in order to capture maximum sunlight. This creates a thick canopy(樹冠)level at the top of the forest, with thinner greenery levels underneath. Some large trees grow so tall that they even tower overthe canopy layer.