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 vpn免费下载 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 itsfood 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 vpn免费下载 the vertebrates, unpredictable Nature selected only snakes (and one lizard)．One wonders vpn软件免费 also why Nature, with some vpn软件免费 snakes, concocted poison of such extreme potency.
In the conversion of saliva into poison, one might suppose that a fixed process took place．It did not; some snakes manufactured a poison different in every respect from that of others, 免费vpn as different as arsenic is from strychnine, and having different effects．One poison acts on the nerves, the other on vpn免费下载 the blood．
The makers of the nerve poison include vpn软件免费 the mambas and the cobras and their 免费vpn venom vpn免费 is called neurotoxic．Vipers (adders) and rattlesnakes manufacture the blood poison, vpn免费 which is known as haemolytic．Both poisons 15are unpleasant, vpn软件免费 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 vpn软件免费 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 免费vpn for use against preysuch as rats and mice, and the effects on these of viperine poison is almost immediate.
JOHN CROMPTON The snake
New words and expressions生词和短语
saliva (1.1) [sə'laivə]n．唾液
conversion (1.10) [kən'və:ʃən] n．转变
digestive (1.2) [di'dʒestiv]adj．助消化的
arsenic (1.11) ['a:snik]n．砒霜
defy (1.2) [di'fai]v．使不可能
strychnine (1.12) ['strikni:n] n．马钱子碱
analysis (1.2) [ə'næləsis]n．分析
mamba (1.13) ['ma:mbə]n．树眼镜蛇
prey (1.3) [prei] n．被捕食的动物
cobra (1.13) ['kəubrə] n．眼镜蛇
fierce (1.6) [fiəs] adj．凶猛的
venom (1.13) ['venəm] vpn软件免费 n．毒液
tussle (1.6) ['tʌsl]n．扭打
neurotoxic (1.13)[ˌnjuərəuˈtɔksik] adj．毒害神经的
carnivore (1.7) ['ka:nivɔ:] n．食肉动物
viper (1.14)['vaipə]n．蝰蛇
vertebrate (1.8) ['və:tibrit]n．脊椎动物
adder (1.14) ['ædə] n．蝮蛇
lizard (1.9) ['lizəd]n．蜥蜴
rattlesnake (1.14) ['rætlsneik] n．响尾蛇
concoct (1.9) [kən'kɔkt] v．调制
haemolytic (1.14)[ˌhi:məu'litik] adj．溶血性的
potency (1.10) ['pəutənsi] n．效力
viperine (1.19) ['vaipərin] adj．毒蛇的
Notes on the text课文注释
1How it came about that snakes…a mystery.
这句话的主语是一个句子：How it came about that snakes manufactured poison，谓语部分是 is a mystery。主语从句中的it是形式主语，真正主语是that snakes manufactured poison，因为主语太长，所以使用it作先行主语的结构。
Refer to the text to see how the following vpn免费下载 words have been used, then write vpn免费下载 sentences of your own using these words: mild (1.1); converted (1.2); defies analysis 免费vpn (1.2); the survival competition (1.3); vpn免费下载 carnivore (1.7); a twoedged weapon (11.7-8); concocted (1.9); extreme potency (1.9); viperine (1.19).
The paragraph段落
ADrawing your information from the first paragraph (lines 1-9), write a list of points in note form to answer the following question: Why is the author justified in stating that Nature behaved in an unpredictable way in allowing snakes to manufacture poison?
BRead the last paragraph again (lines 13-19)．Then, using the list of points given below, reconstruct the paragraph in your vpn免费 own words as far as possible．Do not refer to the passage until you have finished vpn免费 the exercise.
1Nerve poison (e.g．mambas): neurotoxic．
2Blood poison (e.g．vipers): haemolytic．
3Blood poison the more unpleasant.
4Nerve poison possibly the more primitive.
5Blood poison a 免费vpn later development.
6But nerve poison acts more quickly on man.
7Purpose of poison: not vpn软件免费 against man, but snake's prey: e.g．rats.
CWrite a paragraph of about 200 words on one of the following subjects:
1Our vpn免费下载 fear of snakes.
2The survival competition.
Key structures关键句型
ACompare these two vpn免费下载 sentences:
Instead of saying: They had the ability to catch and live on prey without using poison if they wanted to (but they 免费vpn didn't).
We can say: They could have caught and lived on prey without using poison．(1.3)
Write sentences vpn免费 vpn免费下载 using the following expressions:
could have succeeded; could have stayed; could have bought.
BWrite sentences using the following expressions:
force upon (11.2-3); live on (1.3); conversion into (1.10); different from (1.11); act on (1.12); effect on (1.19).
CCompare these two sentences:
Instead of saying: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still catch and live on prey without using poison.
We can say: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still do．(11.3-4)
Complete the following sentences by adding the correct vpn软件免费 form of do:
1Even though he has retired, he still gets up early just as vpn软件免费 vpn免费 he always____.
2He certainly enjoys music as much as you____.
3If you act as he ____ you won't be very vpn免费 popular.
DStudy the following sentence:
Both poisons are unpleasant, but by far the more unpleasant is the blood poison．(11.14-15)
Why is the more used here and not the most?
Write two sentences vpn免费下载 using the more and the most.
ENote how the word far has been added for emphasis in this sentence: Nerve poison does its business … far more quickly than … (1.17)
The word much may be used in the same way．We can say much more quickly, using much in an emphatic way.
Write sentences using the following phrases: much more expensive; far more difficult; far less exciting;much less interesting.
Special difficulties难点
A Study the following pairs of words and then write sentences of your own to bring out the difference.
1merely (1.4)----only
I'm not blaming you．I'm merely trying to find out how this happened．
Only the head of the department can authorize a withdrawal from a course.
2fierce (1.6)----furious
You can see armed guards along the border accompanied by fierce dogs.
He was terribly annoyed．Indeed, he 免费vpn was furious!
3take place (1.10)----take part
All vpn免费 these events took place before you were born.
How many of you are taking part in the play?
4prey (1.3)----pray
The tiger seized its prey and tore it into pieces.
You've done your best．All you can do now is pray for success.
Explain the verbs vpn软件免费 in italics in the following:
How it came about that snakes manufacture poison is a mystery．(1.1)
I'm sorry I said vpn免费 that．I don't vpn免费 know what came over me.
He came up with some very interesting ideas.
I came across an old friend of yours while I was abroad．
CWrite sentences using the following words and phrases: enable (1.4); running 免费vpn fights (1.6); in fact (1.7); in every respect (1.11); so to speak (1.16); be that as it may (11.16-17).
DSupply full stops and commas where necessary in the following paragraph．Do not refer to the passage until you have finished the exercise:
The makers of the nerve poison include the mambas and the cobras and their vpn免费 venom is vpn软件免费 called vpn免费下载 neurotoxic vipers vpn软件免费 (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 vpn软件免费 blood poison is so to speak vpn免费 a newer product from an improved formula be that as it may the nerve poison does its vpn免费 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 vpn软件免费 such as rats and mice and the effects on these 免费vpn of viperine poison is 免费vpn almost immediate．(11.13-19)
Multiple vpn软件免费 choice questions多项选择题
Choose the correct answers to the following questions.
Comprehension理解
1One of these statements is true．Which one?
a．Snakes need poison to vpn免费下载 digest their food．
b．Snakes can feed on other animals without 免费vpn the use of poison.
c．Non-poisonous snakes find survival more difficult than poisonous ones.
d．All snakes are capable of manufacturing poison.
2The possession of poison in the saliva makes hunting ____.
a．easy for all carnivores
b．a two-edged weapon when vpn免费 carnivores fight each other
c．almost effortless for snakes
d．unpredictable, as Nature intended
3The poison that acts on the blood ____.
a．acts less rapidly than nerve vpn免费下载 poison
b．doesn't affect the victim as badly as nerve poison
c．is made by snakes like mambas and cobras
d．was probably the first of the two kinds of 免费vpn poison to be developed
4Human beings ____.
a．can't vpn免费下载 compare with prey such as 免费vpn rats and mice
b．respond to all snake poisons in the same way
c．are likely to survive nerve poison but not blood vpn免费 poison
d．are not the intended victims of snake poison
Structure句型
5They ____ have been able to catch and live on prey without using poison．(1.3)
a．might
b．should
c．would
d．must
6They could have caught and lived on prey without ____ poison．(1.3)
a．to 免费vpn use
b．use
c．the use of
d．have used
7For ____ snakes, poison is merely a luxury．(1.4)
a．these
b．a
c．-
d．an
8Blood poison is the more unpleasant ____．(1.15)
a．of them all
b．of the two
c．in the world
d．among them both
Vocabulary词汇
9Saliva is a natural ____．(11.1-2)
a．oil in the body
b．snake-poison
c．digestive process
d．body fluid
10Poison would be ____ to all carnivores．(1.7)
a．an asset
b．a help
c．a necessity
d．a disadvantage
11Arsenic and strychnine ____ us in different ways．(1.11.11-12)
a．effect
b．result
c．affect
d．cause
12The 免费vpn nerve 免费vpn poison is thought to be ____(11.15-16)
鄂公网安备42010202000179号 )
分享
收藏
