2015考研必背36篇新概念经典作文:Snake poison
— New Concept English Book 3 Lesson 56
Lesson 20 Snake poison蛇毒
First listen and then answer the following question.
听录音,然后回答以下问题。
What are the two different ways in which snake poison acts?
How it came about that snakes manufactured poison is a mystery. Over the periods their saliva, a mild, digestive juice like our own, was converted into a poison that defies analysis even today. It was not forced upon them by the survival competition; they could have caught and lived on prey without using poison, just as the thousands of non-poisonous snakes still do. Poison to a snake is merely a luxury; it enables it to get its food with very little effort, no more effort than one bite. And why only snakes? Cats, for instance, would be greatly helped; no running fights with large, fierce rats or tussles with grown rabbits -- just a bite and no more effort needed. In fact, it would be an assistance to all carnivores though it would be a two-edged weapon when they fought each other. But, of the vertebrates, unpredictable Nature selected only snakes (and one lizard). One wonders saliva into why Nature, with respect from that of others, as other on the blood.
In the conversion of saliva into poison, one might suppose that a fixed process took place. It did not; some snakes manufacture a poison different in every respect from that of others, as different as arsenic is from strychnine, and having different effects. One poison acts on the nerves, the other on the blood.
The makers of the nerve poison include the mambas and the cobras and their venom is called neurotoxic. Vipers (adders) and rattlesnakes manufacture the blood poison, which is known as haemolytic. Both poisons are unpleasant, but by far the more unpleasant is the blood poison. It is said that the nerve poison is the more primitive of the two, that the blood poison is, so to speak, a newer product from an improved formula. Be that as it may, the nerve poison does its business with man far more quickly than the blood poison. This, however, means nothing. Snakes did not acquire their poison for use against man but for use against prey such as rats and mice, and the effects on these of viperine poison is almost immediate.
JOHN CROMPTON The snake
参考译文
蛇是怎样产生毒液的,这是一个谜。蛇的唾液本来和我们人的消化液一样柔和,但经过漫长的时间,演变成了今天仍无法分析清楚的毒液。毒液不是生存竞争强加给它们的,它们也可以不用毒液捕捉动物而生存,就像今天成千上万的无毒蛇那样。毒液对毒蛇来说只不过是一种舒适生存的优越手段,它使蛇不用费多大力气就能捕获到食物,轻咬一口即可。为什么只有蛇才有毒液呢?譬如说,如果猫有毒液,那对猫会大有帮助,它就不必再和又大又凶的老鼠边跑边博斗了,也不必再和大兔子扭斗了,只要咬一口,就不必再费大力气。因此,任何食肉动物有了毒液,都能从中获益。不过,当它们相互撕打时,毒液就成了利弊参半的武,可以杀死对方,也可以被对方的毒液杀死。然而,在脊椎动物中,大自然神秘模测地只选择了蛇(还有一种蜥蜴),人们弄不清楚大自然为什么在某些蛇的身上调制出如此高效的毒液来。
人们可能认为,唾液转变成毒液,其中有固定的程序。其实没有。有些蛇产生的毒液也在各方面与另外一些毒蛇产生的毒液不同,就像砒霜不同于马钱子碱一样。不同毒蛇产生的毒液产生的效果不同,一种毒液作用于神经,另一种毒液作用于血液。
产生神经毒液的蛇有一种非洲树眼镜蛇和眼镜蛇,它们的毒液称为神经毒素。蝰蛇(蝮蛇)和响尾蛇产生血液毒素,称为溶血性毒液。这两种毒液都很可怕,但溶血性毒液尤其厉害。据说,神经毒液在两种毒液中是较为原始的一种,而溶血性毒液,打个比方说,是根据改良配方生产的一种较新的产品。不过,神经毒辣液比溶血性毒液在人身上起作用快得多。但是,这没有什么关系,因为蛇有毒液不是用来对付人的,而是对付它的猎物,诸如鼠类,毒液对这些猎物会立刻起作用。
相关阅读:
2022考研初复试已经接近尾声,考研学子全面进入2023届备考,跨考为23考研的考生准备了10大课包全程准备、全年复习备考计划、目标院校专业辅导、全真复试模拟练习和全程针对性指导;2023考研的小伙伴针也已经开始择校和复习了,跨考考研畅学5.0版本全新升级,无论你在校在家都可以更自如的完成你的考研复习,暑假集训营带来了院校专业初步选择,明确方向;考研备考全年规划,核心知识点入门;个性化制定备考方案,助你赢在起跑线,早出发一点离成功就更近一点!
考研院校专业选择和考研复习计划 | |||
2023备考学习 | 2023线上线下随时学习 | 34所自划线院校考研复试分数线汇总 | |
2022考研复试最全信息整理 | 全国各招生院校考研复试分数线汇总 | ||
2023全日制封闭训练 | 全国各招生院校考研调剂信息汇总 | ||
2023考研先知 | 考研考试科目有哪些? | 如何正确看待考研分数线? | |
不同院校相同专业如何选择更适合自己的 | 从就业说考研如何择专业? | ||
手把手教你如何选专业? | 高校研究生教育各学科门类排行榜 |
相关推荐
跨考考研课程
班型 | 定向班型 | 开班时间 | 高定班 | 标准班 | 课程介绍 | 咨询 |
秋季集训 | 冲刺班 | 9.10-12.20 | 168000 | 24800起 | 小班面授+专业课1对1+专业课定向辅导+协议加强课程(高定班)+专属规划答疑(高定班)+精细化答疑+复试资源(高定班)+复试课包(高定班)+复试指导(高定班)+复试班主任1v1服务(高定班)+复试面授密训(高定班)+复试1v1(高定班) | |
2023集训畅学 | 非定向(政英班/数政英班) | 每月20日 | 22800起(协议班) | 13800起 | 先行阶在线课程+基础阶在线课程+强化阶在线课程+真题阶在线课程+冲刺阶在线课程+专业课针对性一对一课程+班主任全程督学服务+全程规划体系+全程测试体系+全程精细化答疑+择校择专业能力定位体系+全年关键环节指导体系+初试加强课+初试专属服务+复试全科标准班服务 |