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How does Organisms Ward off Invaders
The livelihood of each species in the vast and intricate assemblage of living things depends on the existence of other organisms．This interdependence is sometimes subtle，some times obvious．Perhaps the most straightforward dependence of one species on another occurs with parasites，organisms that live on or in other living things and derive nutrients directly from them．The parasitic way of life is widespread．A multitude of microorganisms(including viruses and bacteria，and an army of invertebrates or creatures lacking a spinal column(including crustaceans，insects，and many different types of worms)make their livings directly at the expense of other creatures．In the face of this onslaught，living things have evolved a variety of defense mechanisms for protecting their bodies from invasion by other organisms．
Certain fungi and even some kinds of bacteria create substances known as antibiotics into their external environment．These substances are capable of killing or inhibiting the growth of various kinds of bacteria that also occupy the area，thereby eliminating or reducing the competition for nutrients．The same principle is used in defense against invaders in other groups of organisms．For example，when attacked by disease--causing fungi or bacteria，many kinds of plants produce chemicals that help to ward off the invaders．
Members of the animal kingdom have developed a variety of defense mechanisms for dealing with parasites．Although these mechanisms vary considerably，all major groups of animals are capable of detecting and reacting to the presence of“foreign”cells．In fact，throughout the animal kingdom from sponges to certain types of wornls shellfish，and all vertebrates(creatures possessing spinal column)
there is evidence that transplants of cells or fragments of tissues into an animal are accepted only if they come from genetically compatible or closely related individuals．
The ability to distinguish between“self”and“non-self”，while present in all animals，is most efficient among vertebrates，which have developed an immune system as their defense mechanism．The immune system recognizes and takes action against foreign invaders and transplanted tissues that are treated as foreign cells．
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Deport them or not
In a country that defines itself by ideals，not by shared blood，who should be allowed to come，work and live here？In the wake of the Sept．1 1 attacks these questions have never seemed more pressing．
On Dec．11，2001，as part of the effort to increase homeland security，federal and local authorities in 14 states staged“Operation Safe Travel”-raids on airports to arrest employees with false identification(身份证明)．In Salt Lake City there were 69 arrests．But those captured were anything but terrorists，most of them
illegal immigrants from Central or South America．Authorities said the undocumented workers’illegal status made them open to blackmail(讹诈)by terrorists．
Many immigrants in Salt Lake City were angered by the arrests and said they felt as if they were being treated like disposable goods．
Mayor Anderson said those feelings were justified to a certain extent，“We’re saying we want you to work in these places，we’re going to look the other way in terms of what our laws are，and then when it’s convenient for us，or when we can try to make a point in terms of national security，especially after Sept．1 1，then you’re disposable．There are whole families being uprooted for all of the wrong reasons，”Anderson said．
If Sept．1 1 had never happened．the airport workers would not have been arrested and could have gone oil quietly living in America．probably indefinitely．Ana Castr0，a manager at a Ben＆Jerry’s ice cream shop at the airport，had been workin9 10 years with the same false Social Security card when she was arrested in the December airport raid．Now she and her family are living under the threat of deportation(驱逐出境)．Castro’s case is currently waiting to be settled．While she awaits the outcome，the government has granted her permission to work here and she has returned to her job at Ben&Jerry’s．
According to the author，the United States claims to be a nation__________． 查看材料
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How to Stay Slim
Here&39;s a familiar version of the boy-meets-girl&39;s situation. A young man has at last plucked up courage to invite a dazzling young lady out to dinner. She has accepted his invitation and he is overjoyed. He is determined to take her to the best restaurant in town, even if it means that he will have to live on memories and hopes during the month to come. When they get to the restaurant, he discovers that this material creature is on a diet. She mustn&39;t eat this and she mustn&39;t drink that. Oh, but of course, she doesn&39;t want to spoil his enjoyment. Let him by all means eat as much fattening food as he wants : it&39;s the surest way to an early grave. They spend a truly memorable evening together and never see each other again.
What miserable dieters are! You can always recognize them from the sour expression on their faces. They spend most of their time turning their noses up at food. They are forever consulting calorie charts ; gazing at themselves in mirrors ; and leaping onto weighing-machines in the bathroom. They spend a lifetime fighting a losing battle against spreading hips, protruding tummies and double chins. Some wage all-out war on FAT. Mere dieting is not enough. They exhaust themselves doing exercises, sweating in sauna baths, being pummeled and massaged by weird machines. The really wealthy diet-mongers pay vast sums for "health cures" . For two weeks they can enter a "nature clinic" and be starved to death for a hundred guineas a week. Don&39;t think it is only the middle-aged who go in for these fads. Many of these bright young things you see are suffering from chronic malnutrition : they are living on nothing but air, water and the goodwill of God.
Dieters undertake to starve themselves of their own free will; so why are they so miserable？ Well, for one thing, they&39;re always .hungry. You can&39;t be hungry and happy at the same time. All the horrible concoctions they eat instead of food leave them permanently dissatisfied. "Wonder food is a complete food, " the advertisement says, "just dissolve a teaspoonful in water." A complete food it may be, but not quite as complete as a juicy steak. And, of course, they&39;re always miserable because they feel so guilty. Hunger just proves too much for them and in the end they lash out and devour five huge guilt-inducing cream cakes at a sitting. And who can blame them ？ At least three times a day they are exposed to temptation. What utter torture it is always watching other tucking into piles of mouth-watering food while you munch a water biscuit and sip unsweetened lemon juice!
The sentence "...he will have to live on memories and hopes during the month to come" indicates the boy__________. 查看材料
The Influence of Western Movie
Whv does the Western movie especially have such a hold(影响)on our inclination？Chiefly，because it offers serious insights into the problem of violence such as can be found almost nowhere else in our culture．One of the well—known peculiarities of modem civilized opinion is its refusal to acknowledge the value of violence．This refusal is a virtue．but like many virtues it involves a certain deliberate blindness and it encourages hypocrisy(虚伪)．We train ourselves to be shocked or bored by cultural images of violence，and our very concept of heroism tends to be a passive one．We are less drawn to the brave young men who kill large numbers of our enemies than to the heroic prisoners who endure torture without surrendering．And in the criticism of popular culture，the presence of images of violence is often assumed to be in itself a sufficient ground for condemnation．
These attitudes，however，have not reduced the element of violence in our culture but have helped to free it from moral control by letting it take on the air of“liberation”．The celebration of acts of violence is left more and more to the irresponsible．The gangster(匪徒)movie，with its numerous variations belongs to a cultural“underground”which praises violence aid sets it against all our higher social attitudes．It is a more“modem”style. than the Western movie，perhaps even more profound，because it confronts industrial society on its own ground—the city and because，like much of our advanced art，it gains its effects by a coarse insistence on its own narrow logic．But it is anti-social resting on fantasies of irresponsible freedom．If we are brought finally to concede to the denial of these fantasies，it is only because they have been shown to be dangerous，not because they have given way to higher values of behavior．
In war movies，certainly，it is possible to present violence within a framework of responsibility．But there is the disadvantage that modem war is a co-operative enterprise in which violence is largely impersonal and heroism belongs to the group more than to the individual．The hero of a war movie is most often simply a leader supposed to be brave；you are supposed to get the job done and stay alive(this too，of course，is a kind of heroic posture，but a new and“practical”one)．At its best，the war movie may represent a more civilized point of view than the Western，and if it were not continually spoiled by ideological sentimentality we might hope to find it developing into a higher form. of drama．But it cannot supply the values we seek in the Western．
The author considers gangster movies to be__________． 查看材料
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