3. Checks and balances system Checks and balances ...

Machines are designed to help restore our intrinsic system of checks and balances of our biology.

A．genetic

B．innate

C．internal

D．inert

A、The Judicial branch can review the laws passed by Congress or executive orders issued by President.

B、The judicial branch is restrained by Congress who has the power to create and eliminate lower federal courts.

C、The President, with the advice and consent of the Senate, has the right to appoint the justices of the Supreme Court.

D、The President can veto laws passed by Congress by letting 10 days pass without signing it.

A、Every debit balance represents an expense.

B、Assets are represented by debit balances.

C、Liabilities are represented by debit balances.

D、Income is included in the list of debit balances.

第一篇 Immune Functions

The immune system is equal incomplexity to the combined intricacies of the brain and nervous system. Thesuccess of the immune system in defending the body relies on a dynamicregulatory com- munication network consisting of millions and millions ofcells. Organized into sets and subsets,these cells pass information back andforth like clouds of bees flying around a hive (蜂巢). The result is a sensitive system of checks andbalances that produces an immune response that is prompt, appropriateeffective, and self-limiting.

At the heart of the immunesystem is the ability to distinguish between self and nonself. When im- munedefenders encounter cells or organisms carrying foreign or nonselfmolecules,the immune troops move quickly to eliminate the intruders(入侵者). Virtually everybody cell carries distinctive molecules that identify it as self. The body's immunedefenses do not normally attack tissues that carry a self-marker. Rather,immune cells and other body cells coexist peaceably in s state known asself-toler- ance. When a normally functioning immune system attacks a nonselfmolecule, the system has the abil- ity to"remember" the specifics ofthe foreign body. Upon subsequent encounters with the same species ofmolecules, the immune system reacts accordingly. With the possible exception ofantibodies(抗体)

passed during lactation (哺乳期),this so called immune system memory is notinherited. Despite the occurrence of a virus in your family, your immune systemmust "learn" from experience with the many millions of distinctivenonself molecules in the sea of microbes(微生物)in which we live. Learning en- tails producing theappropriate molecules and cells to match up with and counteract each nonselfinvader.

Any substance capable oftriggering an immune response is called an antigen(抗原). Antigens are notto be confused with allergens (过敏原), which are most often harmless substances that provoke the immunesystem to set off the inappropriate and harmful response known as allergy. Anantigen can be a virus, a bacterium or even a portion or product of one ofthese organisms. Tissues or cells from another individual also act as antigens;because the immune system recognizes transplanted tissues as foreign, itrejects them. The body will even reject nourishing proteins unless they arefirst brokendown by the digestive system into their primary, nonantigenicbuilding blocks. An antigen announces its for- eignness by means of intricateand characteristic shapes called epitopes(抗原表位) , which protrude(突出) from its surface. Most antigens, even thesimplest microbes, carry several different kinds of epitopes on their surface;some may even carry several hundreds. Some epitopes will be more effective thanothers at stimulating an immune response. Only in abnormal situation does theimmune system wrongly identify self as nonself and execute a misdirected immuneattack.

What is used to describe the communication network consisting of cells in theimmune system?

A.The immune system's memory

B.Immune troops eliminating intruders

C.Bees flying around a hiv

D.A sea of microbes

The balance of nature is a delicate system of checks and counter-checks. Nature has its own way of checking the life and distribution of the different organisms and helping their growth. An epidemic may be considered nature's way of checking population growth. Man in his attempt to conquer nature and to utilise it to his advantage has interfered with the balance of nature, thereby creating problems of a complex nature. Nature's ways of maintaining the balance are intricate and not easily understood and man's application of his scientific knowledge and techniques has upset this balance so much that today, being aware of the disastrous consequences, he takes measures against them.

No animal or plant can live in isolation, for different organisms are parts of a vast dynamic complex of living things. As no man. or community is serf-sufficient, no organism can live by itself. When man interferes with the interdependence and interrelationships of the different organisms, he is, in effect, upsetting their balanced relationships and his action can have a chain reaction. If we prevent fish eggs from being deposited in a pond, we are allowing an unchecked growth of weeds. The waterfowl which feeds on tadpoles will look for alternatives, thereby tending to upset these blanced relationships. It is important that for the preservation of beauty in nature the balance of nature is maintained.

Man for his own survival has to make his peace with plant and animal life, the size and distribution of which he has interfered with. It is to be noted that in every plant and animal community there is a trend towards a balance between the different species. When each successive species is of. the right number to maintain a constant population, a balance between the different species is maintained and this state is referred to as the climax stage. Man is forever upsetting the balance of the climax stage. He has added to the numbers of animals and plants that are useful to him. In the process he has unwittingly helped the increase in the number of insects and vermin and as a result he has to wage a relentless war against them. if man continues to interfere with the balance of nature, it is possible that some animals and birds may soon become extinct. The indiscriminate hunting of whales has reduced the number of some species almost to the verge of extinction and international laws have been drawn up to protect them.

The balance of nature is to be maintained in order to prevent soil deterioration. Human intervention has altered the established relationship between the plants of an area and the soil of that area. Animals introduced by man, sheep and goats for example, have led to widespread soil deterioration. By cutting down trees or by practising unsuitable systems of agriculture, man destroys the crumb structure of soil, thereby making it susceptible to erosion. Soil erosion results in loss of soil fertility and maintaining soil fertility is considered the biggest problem facing mankind apart from the prevention of war. The increase in world population and the growth of civilisation have been the two major factors that have led man to cut down forests on an unprecedented scale and the erosion caused by the cutting down of huge areas of forests has resulted in floods on a scale hitherto unknown. Soil erosion can whittle away soil fertility and if adequate and effective measures are not taken it can become a menacing spectre tearing at the prosperity of many countries.

Pollution, in its different forms, interferes with the balance of nature. Water pollution affects nature's balance in oceans, lakes and rivers. Man-made pollution of water is due to municipal sewage, dumping by factories and the depositing of pesticides. Solid wastes can permeate the soil and pollute lakes and rivers.

Man has to adopt the philosophy of thrift by conserving natural resources and not destroying the

A．simple and easily understood

B．intricate and not easily understood

C．mysterious and unknown

D．everchanging

A、prevent the government from misusing its power

B、prevent the government from being strong

C、pacify those who opposed the Constitution

D、meet the demands of small states