问题 单项选择题

阅读以下文字,完成46—50题。鲸鱼不同于其他鱼类,是温血动物,从冰天雪地的南、北极到酷热的赤道都可以看到鲸鱼的踪迹,无论是在什么样的环境下,鲸鱼的体温均保持在36℃左右,常在极圈活动的鲸鱼会具有局部异温功能。像鲸鱼、海豹和海豚这些大部分时间或一直都待在海里的哺乳动物,用特殊的高级脂肪“外衣”保持自己的体温。但对于那些必须通过潜水进行捕食的动物来说,光有皮毛保护是不够的,因为厚重毛发里的空气会被极强的水压挤出来,皮毛的保温功能会大大降低。而北冰洋和南极周围的海洋深水水温可以降至零下40度,没有其他的保暖措施显然不行。鲸鱼和其他温血动物最大的不同点在于,其活动环境是在较低温的水中,水有相当大的比热及传热能力,因此温度变化很快,鲸鱼无法以聚集、筑巢等方式维持体温,于是演化出超厚的皮下脂肪。过去曾记录到鲸鱼脂肪厚达50公分。鲸脂是一层包裹整个身体的厚重脂肪“外衣”,重量可以达到体重的一半!这层脂肪含有细细的血管组织,除帮助保持体温,还为很多需要长途跋涉进行繁殖和觅食的海洋动物提供了重要能量储备。除此之外,这层脂肪还可以帮助快速游动的动物将身体塑造成流线型,减少在水中游动时所消耗的能量,同时提高速度。动物栖身的海水温度越冷,其自身的脂肪也就越厚。鲸脂是通过吸食母体乳液获得的。举例来说,一只灰鲸幼仔每天要喝掉30加仑乳液,这些乳液的功能相当于人造黄油。但这么厚的皮下脂肪还是不能完全阻挡体温外流,因此鲸鱼还需要摄取大量食物,维持身体体温所需能量。鲸鱼的前鳍、尾鳍、背鳍并无鲸脂的分布,当鲸鱼潜到阳光照射不到的深海,或是南、北极时,鲸鱼的鱼鳍难道不会冻到无法活动吗?对此,鲸鱼鳍上的动脉分为无数平行的小动脉,每条小动脉周围又被许多纵行的静脉血管包围,形成一个个血管束,利用动脉与静脉的紧密接触减少热能的散失,这点和企鹅脚不怕冷的道理是一样的。这个特别的系统,主要控制鲸鳍末端有可能散失的热,继而保持体温,但当鲸鱼因为活动,所产生的体热增加时,这个机制就会自行关闭,动脉血将一直保持着原有的温度到达鳍肢,并把过多的热量散发出去,中途就不再把一部分热量传递给静脉。此外,鲸鱼还会透过血管的收缩,有效维持体温,当鲸鱼潜进深海中时,周围温度低,鲸鱼体表的血管会收缩,将血液集中送往脑部、心脏、肝、肾等内脏器官,从而维持内部体温;相反的,当水温上升时,体表的血管便会扩张,加速散热。

鲸鱼在进入深海水域时通常()。

A.开始大量消耗鲸脂

B.开启鲸鳍的血管束系统

C.体温与水温保持一致

D.减少活动量和捕食量

答案

参考答案:B

解析:鲸脂的消耗在文中只是提到运动时会消耗,但低温时会不会自动大量消耗并没有提及,所以A项错误。 文章第一段提到“无论是在什么样的环境下,鲸鱼的体温均保持在36℃左右”,所以不可能与深海水域的水温保持一致,C项错误。 鲸鱼在进入深海水域时,外界温度降低,其自身应该增加热量以抵消热量的散失,但减少活动量和捕食量显然不利于热量的增加,不合常理,当然D项内容文章本身也没有提及,故错误。 根据第五段可知,B项功能就是为了解决“鲸鱼潜到阳光照射不到的深海”时鱼鳍保温的问题,所以B项正确。故选B。

单项选择题
阅读理解

阅读理解。

     Two hours from the tall buildings of Manhattan and Philadelphia live some of the world's largest black

bears. They are in northern Pennsylvania's Pocono Mountains, a home they share with an abundance of

other wildlife.

     The streams, lakes, meadows, mountain ridges and forests that make the Poconos an ideal place for

black bears,have also attracted more people to the region. Open spaces are threatened by plans for housing

estates and important habitats are endangered by highway construction. To protect the Poconos' natural

beauty from irresponsible development, the Nature Conservancy (大自然保护协会) named the area one

of America's "Last Great Places"

     Operating out of a century-old schoolhouse in the village of Long Pond, Pennsylvania, the

conservancy's bud Cook is working with local people and business leaders to balance economic growth

with environmental protection. By forging partnerships with people like Francis Altemose, the Conservancy

has been able to protect more than 14,000 acres of environmentally important land in the area.

      Altemose's family has farmed in the Pocono area for generations. Two years ago Francis worked with

the Conservancy to include his farm in a county farmland protection program. As a result, his family's land

can be protected from development and the Altemoses will be better able to provide a secure financial future

for their 7-year-old grandson. Cook attributes the Conservancy's success in the Poconos to having a local

presence and a commitment to working with local residents

      "The key to protecting these remarkable lands is connecting with the local community," Cook said. "The

people who live there respect the land. They value quite forests, clear streams and abundant wildlife. They are

eager to help with conservation effort. For more information on how you can help The Nature Conservancy

protect the Poconos and the world's other"Last Great Places," please call 1-888-564 6864, or visit us on the

World Wide Web at www.tnc.org.

1. The purpose in naming the Poconos as one of America's " Last Great Places" is to ________.

A. gain support from the local community

B. protect it from irresponsible development

C. make it a better home for black bears

D. provide financial security for future generations

2. We learn from the passage that _______.

A. the population in the Pocono area is growing

B. wildlife in the Pocono area is dying out rapidly

C. the security of the Pocono residents is being threatened

D. farmlands in the Pocono area are shrinking fast

3. What is important in protecting the Poconos according to Cook?

A. The setting up of an environmental protection website

B. Support from organizations like The Nature Conservancy

C. Cooperation with the local residents and business leaders

D. Inclusion of farmlands in the region's protection program

4. The passage most probably is ________.

A. an official document

B. a news story

C. an advertisement

D. a research report