1、Unit 2 Cloning.阅读理解Have you seen Jurassic Park? In this film, scientists use DNA kept for tens of millions of years to clone dinosaurs. They find trouble，however，when they realize that the cloned creatures are smarter and more dangerous than expected. Thats nothing more than a fiction.But could we r
2、eally clone endangered animals?To date, the most successful attempt to do so was the cloning of a gaur，a rare oxlike animal from southeast Asia. Scientists used a cow to bring the cloned baby gaur, named Noah. Two days after birth，however，Noah died from a common bacterial infection.Other endangered
3、species that may be cloned include the African bongo antelope(羚羊), the Sumatran tiger, the cheetah(猎豹), and the giant panda.Next，could we really clone extinct animals?In theory？Yes.To do this, you need a wellkept source of DNA from the extinct animals such as wool mammoth(毛象)，Tasmanian tiger，or even
4、 dinosaur, and a closely related species, still living，which could serve as a_surrogate_mother.In reality? Probably not. On the one hand, its not likely that extinct animals DNA could survive undamaged for such a long time. Cloning such extinct animals as wool mammoth, Tasmanian tiger，or dinosaur is
5、 much more difficult due to the lack of properly wellpreserved DNA. On the other hand, for example, a gaur can have a cow as a surrogate mother, definitely not a monkey. But what about an extinct animal as unique as the panda? What species could possibly serve as a surrogate mother?Cloning presents
6、many exciting possibilities.However, even if extinct animals were brought back，they could not survive in todays world. Not only do most extinct animals have no habitat to live in, but the other plants and animals they depended on for food may also be gone as well.本文说明了在克隆灭绝动物的过程中遇到的种种困难与障碍。即使克隆成功了，其
7、赖以生存的食物链也已经被破坏，被克隆出来的动物也无法继续走下去。1It can be learned from the text that _.Athe gaur is an extinct speciesBthe gaur lives in Asia and is endangeredCscientists have cloned the African bongo antelopeDboth the cheetah and the giant panda live in Asia答案：B解析：细节理解题。根据第二、三段可知，印度野牛生活在亚洲的东南部，濒临灭绝。2The underline
8、d words “a surrogate mother” probably refer to a female who _.Agives birth to a baby of its ownBcannot give birth to a babyCgives birth to a baby for another femaleDprovides DNA答案：C解析：词义猜测题。根据第五段的描述可知，此处表示的是，把一种动物的DNA提取出来之后，在另外一种动物的体内进行胚胎繁殖，而这种动物就被称为a surrogate mother，由此判断，画线部分意思为“代孕妈妈”，故C项正确。3The d
9、ifficulty in cloning an extinct species is the lack of _.Aboth the wellpreserved DNA and a surrogate motherBboth the habitat to live in and the wellpreserved DNACboth the wellpreserved DNA and plants to live onDboth the habitat to live in and plants to live on答案：A解析：细节理解题。根据文章倒数第二段中的“On the one hand
10、.On the other hand.”两个方面的表述可知，克隆的困难在于一是要寻找灭绝动物的保存完好的DNA，二是要寻找到合适的代孕的物种，故A项正确。4In the authors opinion, it is possible that _.Aall the extinct species may be clonedBextinct species may be cloned and easily surviveCa gaur can have a monkey as a surrogate motherDsome extinct species may be cloned, but n
11、ot survive答案：D解析：细节理解题。根据最后一段的表述可知，也许克隆存在众多的可能性，但是即使克隆成功了，也许会由于其赖以生存的食物链已经被破坏而无法继续存活下去。由此判断D项正确。.语法填空The polar bear is found in the Arctic Circle and some big land masses as far south as Newfoundland.While they are rare north of 88，there is evidence _1_ they range all the way across the Arctic，and a
12、s far south as James Bay in Canada. It is difficult to figure out a global population of polar bears as much of the range has been _2_ (poor) studied；however，biologists calculate that there are about 20,00025,000 polar bears worldwide.Modern methods _3_ tracking polar bear populations have been empl
13、oyed only since the mid1980s，and are expensive _4_(perform) consistently over a large area.In recent years some Inuit people in Nunavut _5_(report) increases in bear sightings around human settlements，leading to a _6_(believe) that populations are increasing.Scientists have responded by _7_(note) th
14、at hungry bears may be congregating (聚集) around human settlements，leading to the illusion (错觉) that populations are _8_(high) than they actually are. Of _9_ nineteen recognized polar bear subpopulations，three are declining，six _10_(be) stable，one is increasing, and nine lack enough data.1that解析：考查同位
15、语从句的引导词。分析句子结构可知，所填词引导同位语从句，解释说明evidence的具体内容，从句中不缺少成分且意义完整，故用that引导。2poorly解析：考查词性转换。修饰动词studied应用形容词poor的副词形式poorly。3of/for解析：考查介词。a method of/for doing sth.“做某事的方法”。4to_perform解析：考查非谓语动词。此处是“主语beadj.不定式”结构，不定式用主动形式表示被动含义。5have_reported解析：考查动词的时态。根据句中的时间状语in recent years可判断用现在完成时。6belief解析：考查词性转换。根据空格前的不定冠词a可知，此处应填believe的名词形式belief(看法，信念)。7noting解析：考查非谓语动词。介词后接动词时，应用其动名词形式。respond by doing sth.“通过做某事回应”。8higher解析：考查形容词比较级。根据空格后的than可知，此处应用high的比较级形式higher。9the解析：考查冠词。此处特指确认的19个北极熊亚种群，故用定冠词the。10are解析：考查动词的时态和主谓一致。此处陈述客观事实，应用一般现在时；six指代six polar bear subpopulations，谓语动词应用复数。
