[外语类试卷]大学英语六级模拟试卷346及答案与解析.doc
《[外语类试卷]大学英语六级模拟试卷346及答案与解析.doc》由会员分享,可在线阅读,更多相关《[外语类试卷]大学英语六级模拟试卷346及答案与解析.doc(38页珍藏版)》请在麦多课文档分享上搜索。
1、大学英语六级模拟试卷 346及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a short essay entitled on Graduate Mania. You should write at least 150 words following the outline given below. 1. 目前很多人报考研究生; 2. 你认为 此现象的原因是什么; 3. 你的看法。 二、 Part II Reading Comprehen
2、sion (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark: Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the stat
3、ement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Rain forests Tropical rainforests are the most diverse ecosystem (生态系统 ) on Earth, and also the oldest. Today, tropical rainforests cover only 6 percent of the Earths ground s
4、urface, but they are home to over half of the planets 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 whe
5、n 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 st
6、eady climate is due to the position of rainforests on the globe. Because of the orientation of the Earths 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 arc not especia
7、lly 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 resource
8、s 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 (树冠 ) level at the to
9、p of the forest, with thinner greenery levels underneath. Some large trees grow so tall that they even tower over the canopy layer. As you go lower, down into the rainforest, you find less and less greenery. The forest floor is made up of moss, fungi, and decaying plant matter that has fallen from t
10、he upper layers. The reason for this decrease in greenery is very simple the overabundance of plants gathering sunlight at the top of the forest blocks most sunlight from reaching the bottom of the forest, making it difficult for robust plants to thrive. The Forest for the Trees The ample sunlight a
11、nd extremely wet climate of many tropical areas encourage the growth of towering trees with wide canopies. This thick top layer of the rainforest dictates the lives of all other plants in the forest. New tree seedlings rarely survive to make it to the top unless some older trees die, creating a “hol
12、e“ in the canopy. When this happens, all of the seedlings on the ground level compete intensely to reach the sunlight. Many plant species reach the top of the forest by climbing the tall trees. It is much easier to ascend this way, because the plant doesnt have to form its own supporting structure.
13、Some plant species, called epiphytes, grow directly on the surface of the giant trees. These plants, which include a variety of orchids and ferns, make up much of the understory, the layer of the rainforest right below the canopy. Epiphytes are close enough to the top to receive adequate light, and
14、the runoff from the canopy layer provides all the water and nutrients(养分 )they need, which is important since they dont have access to the nutrients in the ground. Stranglers and Buttresses Some epiphytes eventually develop into stranglers. They grow long, thick roots that extend down the tree trunk
15、 into the ground. As they continue to grow, the roots form a sort of web structure all around the tree. At the same time, the strangler plants branches extend upward, spreading out into the canopy. Eventually, the strangler may block so much light from above, and absorb such a high percentage of nut
16、rients from the ground below, that the host tree dies. Competition over nutrients is almost as intense as competition for light. The excessive rainfall rapidly dissolves nutrients in the soil making it relatively infertile except at the top layers. For this reason, rainforest tree roots grow outward
17、 to cover a wider area, rather than downward to lower levels. This makes rainforest trees somewhat unstable, since they dont have very strong anchors in the ground. Some trees compensate for this by growing natural buttresses. These buttresses are basically tree trunks that extend out from the side
18、of the tree and clown to the ground, giving the tree additional support. Rainforest trees are dependent on bacteria that are continually producing nutrients in the ground. Rainforest bacteria and trees have a very close, symbiotic (共生的 ) relationship. The trees provide the bacteria with food, in the
19、 form of fallen leaves and other material, and the bacteria break this material down into the nutrients that the trees need to survive. One of the most remarkable things about rainforest plant life is its diversity. The temperate rainforests of the Pacific Northwest are mainly composed of a dozen or
20、 so tree species. A tropical rainforest, on the other hand, might have 300 distinct tree species. All Creatures, Great and Small Rainforests are home to the majority of animal species in the world. And a great number of species who now live in other environments, including humans, originally inhabit
21、ed the rainforests. Researchers estimate that in a large rainforest area, there may be more than 10 million different animal species. Most of these species have adapted for life in the upper levels of the rainforest, where food is most plentiful. Insects, which can easily climb or fly from tree to t
22、ree, make up the largest group (ants are the most abundant animal in the rainforest). Insect species have a highly symbiotic relationship with the plant life in a rainforest. The insects move from plant to plant, enjoying the wealth of food provided there. As they travel, the insects may pick up the
23、 plants seeds, dropping them some distance away. This helps to disperse the population of the plant species over a larger area. The numerous birds of the rainforest also play a major part in seed dispersal. When they eat fruit from a plant, the seeds pass through their digestive system. By the time
24、they excrete (排泄 ) the seeds, the birds may have flown many miles away from the fruit-bearing tree. There are also a large number of reptiles and mammals in the rainforest. Since the weather is so hot and humid during the day, most rainforest mammals are active only at night, dusk or dawn. The many
- 1.请仔细阅读文档,确保文档完整性,对于不预览、不比对内容而直接下载带来的问题本站不予受理。
- 2.下载的文档,不会出现我们的网址水印。
- 3、该文档所得收入(下载+内容+预览)归上传者、原创作者;如果您是本文档原作者,请点此认领!既往收益都归您。
下载文档到电脑,查找使用更方便
2000 积分 0人已下载
下载 | 加入VIP,交流精品资源 |
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 外语类 试卷 大学 英语六级 模拟 346 答案 解析 DOC
