关闭图标
log图标

www.toeflonline.cn

  • 使用手机注册
  • 使用邮箱注册
  • 手机号不能为空!

    验证码不能为空!

    用户名不能为空!

    密码不能为空!

  • 邮箱不能为空!

    验证码不能为空!

    用户名不能为空!

    密码不能为空!

已有账号? 登录到雷哥托福
关闭图标
log图标
  • 使用手机找回密码
  • 使用邮箱找回密码
  • 手机号不能为空!

    验证码不能为空!

    密码不能为空!

  • 邮箱不能为空!

    验证码不能为空!

    密码不能为空!

又想起来了
加入生词本

listen

英['lɪs(ə)n] 美['lɪsn]
vi. 听,倾听;听从,听信
n. 听,倾听

已添加
×

我要举报草莓小菇凉评论

用户头像
草莓小菇凉:说的非常好,十分有道理,棒棒棒!

06-08 15:44:55

请选择举报类型:

举报电话:400-6021-727    举报QQ:2095453331
×
logo图标
分享到雷哥托福

分享成功图标分享成功

邀请名师点评成功,管理员正在安排老师进行点评。

继续做题 返回首页
支付雷豆失败图标 雷豆余额不足 购买雷豆 返回
报告题目错误
请选择错误类型:
请描述一下这个错误:

取消

TPO-15-A Warm Blooded Turtle

When it comes to physiology, the leatherback turtle is, in some ways, more like a reptilian whale than a turtle. It swims farther into the cold of the northern and southern oceans than any other sea turtle, and it deals with the chilly waters in a way unique among reptiles.

A warm-blooded turtle may seem to be a contradiction in terms. Nonetheless, an adult leatherback can maintain a body temperature of between 25 and 26°C (77-79°F) in seawater that is only 8°C (46.4°F). Accomplishing this feat requires adaptations both to generate heat in the turtle’s body and to keep it from escaping into the surrounding waters. Leatherbacks apparently do not generate internal heat the way we do, or the way birds do, as a by-product of cellular metabolism. A leatherback may be able to pick up some body heat by basking at the surface; its dark, almost black body color may help it to absorb solar radiation. However, most of its internal heat comes from the action of its muscles.

Leatherbacks keep their body heat in three different ways. The first, and simplest, is size. The bigger the animal is, the lower its surface-to-volume ratio; for every ounce of body mass, there is proportionately less surface through which heat can escape. An adult leatherback is twice the size of the biggest cheloniid sea turtles and will therefore take longer to cool off. Maintaining a high body temperature through sheer bulk is called gigantothermy. It works for elephants, for whales, and, perhaps, it worked for many of the larger dinosaurs. It apparently works, in a smaller way, for some other sea turtles. Large loggerhead and green turtles can maintain their body temperature at a degree or two above that of the surrounding water, and gigantothermy is probably the way they do it. Muscular activity helps, too, and an actively swimming green turtle may be 7°C (12.6°F) warmer than the waters it swims through.

Gigantothermy, though, would not be enough to keep a leatherback warm in cold northern waters. It is not enough for whales, which supplement it with a thick layer of insulating blubber (fat). Leatherbacks do not have blubber, but they do have a reptilian equivalent: thick, oil-saturated skin, with a layer of fibrous, fatty tissue just beneath it. Insulation protects the leatherback everywhere but on its head and flippers. Because the flippers are comparatively thin and blade-like, they are the one part of the leatherback that is likely to become chilled. There is not much that the turtle can do about this without compromising the aerodynamic shape of the flipper. The problem is that as blood flows through the turtle’s flippers, it risks losing enough heat to lower the animal’s central body temperature when it returns. The solution is to allow the flippers to cool down without drawing heat away from the rest of the turtle’s body. The leatherback accomplishes this by arranging the blood vessels in the base of its flipper into a countercurrent exchange system.

In a countercurrent exchange system, the blood vessels carrying cooled blood from the flippers run close enough to the blood vessels carrying warm blood from the body to pick up some heat from the warmer blood vessels; thus, the heat is transferred from the outgoing to the ingoing vessels before it reaches the flipper itself. This is the same arrangement found in an old-fashioned steam radiator, in which the coiled pipes pass heat back and forth as water courses through them. The leatherback is certainly not the only animal with such an arrangement; gulls have a countercurrent exchange in their legs. That is why a gull can stand on an ice floe without freezing.

All this applies, of course, only to an adult leatherback. Hatchlings are simply too small to conserve body heat, even with insulation and countercurrent exchange systems. We do not know how old, or how large, a leatherback has to be before it can switch from a cold-blooded to a warm-blooded mode of life. Leatherbacks reach their immense size in a much shorter time than it takes other sea turtles to grow. Perhaps their rush to adulthood is driven by a simple need to keep warm.

谈到生理学,棱皮龟在某种程度上更像是一只爬虫,而不是一只乌龟。它比任何其他的海龟更深入地游到北部和南部海洋的寒冷中,它以爬行动物中独特的方式处理寒冷的水域。

 

温血龟似乎是矛盾的。尽管如此,一个成年的棱皮可以在仅8°C(46.4°F)的海水中保持25至26°C(77-79°F)的体温。要完成这个壮举,需要适应龟体内产生的热量,并防止它逃逸到周围的水域。皮革显然不像我们所做的那样产生内部热量,也不像鸟类那样产生细胞代谢的副产品。一个棱皮可以通过在表面上晒太阳来吸收一些体温,其黑暗,几乎黑色的身体颜色可能有助于它吸收太阳辐射。然而,其内部的大部分热量来自肌肉的作用。

 

皮革背部以三种不同的方式保持身体的热量。第一个也是最简单的就是尺寸。动物越大,其表面积与体积比越低;对于每一盎司的体重来说,热量可以通过的比例较小。一个成年的棱皮是最大的龟龟的两倍,因此需要更长的时间来冷却。通过纯粹的体积保持高的体温称为巨大的体温。它适用于大象,鲸鱼,也许适用于很多大型恐龙。它显然是以更小的方式用于其他一些海龟。大log龟和绿海龟的体温可能比周围水温高一两度,巨大的温度可能就是这样做的。肌肉活动也有帮助,一只积极游泳的绿海龟比它游过的海水温度高7°C(12.6°F)。

 

然而,巨大的温度不足以在北部寒冷的水域保持棱皮的温暖。对于鲸鱼来说,这是不够的,它补充了一层厚厚的绝缘脂肪(脂肪)。棱皮没有鲸脂,但它们的确有一种爬行类动物:厚厚的,油饱和的皮肤,下方有一层纤维状的脂肪组织。绝缘保护皮革到处都是,但它的头部和鳍状肢。由于脚蹼比较薄且呈刀刃状,因此它们是可能变冷的棱皮的一部分。龟没有太多的可以做这个,而不妥协的脚蹼的空气动力学形状。问题是,当血液流过龟的鳍状肢时,有可能失去足够的热量来降低动物返回时的中心体温。解决的办法是让脚蹼冷却下来,而不用从龟体的其余部分吸走热量。皮革装置通过将鳍状肢底部的血管布置成逆流交换系统来实现这一点。

 

在逆流交换系统中,携带来自鳍状肢的冷却血液的血管足够接近携带来自身体的温血的血管,以从较暖和的血管获取一些热量;因此,热量在到达鳍状物本身之前从输出到输入的器皿转移。这与老式蒸汽散热器中的安排是一样的,在这个蒸汽散热器中,盘绕的管子像水道一样来回传递热量。皮革当然不是唯一具有这种安排的动物;海鸥腿上有逆流交换。这就是为什么一只鸥能够在没有冻结的情况下站在浮冰上。

 

所有这一切当然只适用于成人皮革。幼鱼体积太小,无法保持体温,即使采用隔热和逆流交换系统。我们不知道皮革背后有多大的年代,或者有多大的年龄,才能从冷血型转向温血型的生活方式。皮革背甲在比其他海龟成长更短的时间内达到了巨大的规模。也许他们急于成年是由一个简单的需要保持温暖。


中文翻译

The phrase “unique among” in the passage is closest in meaning to

  • It swims farther into the cold of the northern and southern oceans than any other sea turtle, and it deals with the chilly waters in a way unique among reptiles. A natural to B different from all other C quite common among D familiar to unique among
正确答案: B

网友解析

  • 用户头像

    joannazz  发表于 2018-01-16 11:34:35

    词汇题
    解析:unique独特的,与B最近

题目讨论

雷哥托福微信

  • 微信公众号:toeflgo

    二维码
  • 小托君:Toefl12345

    二维码
查看详情图片

您已提交评论成功

确定