PASSAGE 2 – Questions 11-20

Anyone who has handled a fossilized bone knows that it is usually not exactly like its modern counterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone and other tissues have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is a wrong interpretation; fossils are frequently so dense because the pores and other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up but little from their surroundings. Probably all of the numerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bone, even in bone as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structure of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too — it has the same crystal structure as that of modern bone.

Although nothing remains of the original collagen, some of its component amino acids are usually still detectable, together with amino acids of the non-collagen proteins of bone.

PASSAGE 2 – Questions 11-20

Anyone who has handled a fossilized bone knows that it is usually not exactly like its modern counterpart, the most obvious difference being that it is often much heavier. Fossils often have the quality of stone rather than of organic materials, and this has led to the use of the term "petrifaction" (to bring about rock). The implication is that bone and other tissues have somehow been turned into stone, and this is certainly the explanation given in some texts. But it is a wrong interpretation; fossils are frequently so dense because the pores and other spaces in the bone have become filled with minerals taken up from the surrounding sediments. Some fossil bones have all the interstitial spaces filled with foreign minerals, including the marrow cavity, if there is one, while others have taken up but little from their surroundings. Probably all of the numerals deposited within the bone have been recrystallized from solution by the action of water percolating through them. The degree of mineralization appears to be determined by the nature of the environment in which the bone was deposited and not by the antiquity of the bone. For example, the black fossil bones that are so common in many parts of Florida are heavily mineralized, but they are only about 20,000 years old, whereas many of the dinosaur bones from western Canada, which are about 75 million years old, are only partially filled in. Under optimum conditions the process of mineralization probably takes thousands rather than millions of years, perhaps considerably less.

The amount of change that has occurred in fossil bone, even in bone as old as that of dinosaurs, is often remarkably small. We are therefore usually able to see the microscopic structure of the bone, including such fine details as the lacunae where the living bone cells once resided. The natural bone mineral, the hydroxyapatite, is virtually unaltered too — it has the same crystal structure as that of modern bone.

Although nothing remains of the original collagen, some of its component amino acids are usually still detectable, together with amino acids of the non-collagen proteins of bone.

Câu 11: What does the passage mainly discuss?

PASSAGE 3 – Questions 21-30

Impeachment

Under the Constitution, the House of Representatives has the power to impeach a government official, in effect serving as prosecutor. The Senate then holds the impeachment trial, essentially serving as jury and judge, except in the impeachment of a president when the chief justice presides. The president, vice president, and all civil officers of the United States are subject to impeachment; conviction means automatic removal from office.

The concept of impeachment originated in England and was adopted by many of the American colonial governments and state constitutions. At the Constitutional Convention, the framers considered several possible models before deciding that the Senate should try impeachments. Since 1789, only 17 federal officers have been impeached by the House, 14 of which were tried by the Senate. Three were dismissed before trial because the individual had left office, 7 ended in acquittal and 7 in conviction. All of those convicted were federal judges.

Impeachment is a very serious affair. It is perhaps the most awesome power of Congress, the ultimate weapon it wields against officials of the federal government. The House of Representatives is the prosecutor. The Senate chamber is the courtroom. The Senate is the jury and also the judge, except in the case of a presidential impeachment trial when the chief justice presides. The final penalty is removal from office. There is no appeal.

So grave is this power of impeachment, and so conscious is the Congress of this solemn power, that impeachment proceedings have been initiated in the House only sixty-two times since 1789. Only seventeen federal officers have been impeached: two presidents, one cabinet officer, one senator and thirteen federal judges. Sixteen cases have reached the Senate. Of these, two were dismissed before trial because the individuals had left office, seven ended in acquittal, and seven in conviction. Each of the seven Senate convictions has involved a federal judge.

The American colonial governments and early state constitutions followed the British pattern of trial before the upper legislative body on charges brought by the lower house. Despite these precedents, a major controversy arose at the Constitutional Convention about whether the Senate should act as the court of impeachment. Opposing that role for the Senate, James Madison and Charles Cotesworth Pinckney asserted that it would make the president too dependent on the legislative branch. They suggested, as alternative trial bodies, the Supreme Court or the chief justices of the state supreme courts. Hamilton and others argued, however, that such bodies would be too small and susceptible to corruption. In the end, after much wrangling, the framers selected the Senate as the trial forum.

There was also considerable debate at the convention in Philadelphia over the definition of impeachable crimes. In the original proposals, the president was to be removed on impeachment and conviction "for mal or corrupt conduct," or for "malpractice or neglect of duty." Later, the wording was changed to "treason, bribery, or corruption," then to "treason or bribery" alone. A final revision defined impeachable crimes as "treason, bribery, or other high crimes and misdemeanors."

In the Constitution, the House is given the "sole power of impeachment." To the Senate is given "the sole power to try all impeachments." Impeachments may be brought against "the President, Vice President, and all civil officers of the United States." Conviction is automatically followed by "removal from office."

While the framers very clearly envisaged the general necessity of initiating impeachment proceedings, they put in place only a general framework. [A] They left many questions open to differences of opinion and many details to be filled in. [B] Despite the open-endedness, as Peter Charles Hoffer and N.E.H. Hull note in their book Impeachment in America 1635-1805, thanks to the framers: a tool used in Parliament to curb kings and punish placemen was molded into an efficient legislative check upon executive and judicial wrongdoing. [C] The power of the English House of Commons to impeach anyone, for almost any alleged offense, was restrained; the threat of death and forfeiture upon conviction was lifted; and the interference of the Commons and the House of Lords with the regular courts of justice was limited. [D] American impeachment law shifted, at first inadvertently and then deliberately, from the orbit of English precedent to a native republican course. Federal constitutional provisions for impeachment reflected indigenous experience and revolutionary tenets instead of English tradition.

Câu 21: The word "power" in the passage is closest in meaning to ___________

PASSAGE 4 – Questions 31-40

"Producers, Consumers, and Decomposers"

Organisms that are capable of using carbon dioxide as their sole source of carbon are called autotrophs (self-feeders), or producers. These are the plants. They chemically fix carbon through photosynthesis. Organisms that depend on producers as their carbon source are called heterotrophs (feed on others), or consumers. Generally, these are animals. From the producers, which manufacture their own food, energy flows through the system along a circuit called the food chain, reaching consumers and eventually detritivores. Organisms that share the same basic foods are said to be at the same trophic level. Ecosystems generally are structured in a food web, a complex network of interconnected food chains. In a food web, consumers participate in several different food chains, comprising both strong interactions and weak interactions between species in the food web.

Primary consumers feed on producers. [A] Because producers are always plants, the primary consumer is called an herbivore, or plant eater. A carnivore is a secondary consumer and primarily eats meat. [B] A consumer that feeds on both producers (plants) and consumers (meat) is called an omnivore. [C]

Detritivores (detritus feeders and decomposers) are the final link in the endless chain. [D] Detritivores renew the entire system by releasing simple inorganic compounds and nutrients with the breaking down of organic materials. Detritus refers to all the dead organic debris-remains, fallen leaves, and wastes-that living processes leave. Detritus feeders-worms, mites, termites, centipedes, snails, crabs, and even vultures, among others work like an army to consume detritus and excrete nutrients that fuel an ecosystem. Decomposers are primarily bacteria and fungi that digest organic debris outside their bodies and absorb and release nutrients in the process. This metabolic work of microbial decomposers produces the rotting that breaks down detritus. Detritus feeders and decomposers, although different in operation, have a similar function in an ecosystem.

An example of a complex community is the oceanic food web that includes krill, a primary consumer. Krill is a shrimplike crustacean that is a major food for an interrelated group of organisms, including whales, fish, seabirds, seals, and squid in the Antarctic region. All of these organisms participate in numerous other food chains as well, some consuming and some being consumed. Phytoplankton begin this chain by harvesting solar energy in photosynthesis. Herbivorous zooplankton such as krill and other organisms eat Phytoplankton. Consumers eat krill at the next trophic level. Because krill are a protein-rich, plentiful food, they are a major link in this food web. To obtain krill, international factory ships, such as those from Japan and Russia, seek them out. The annual krill harvest currently supplies a million tons, principally as feed for chickens and livestock and as protein for human consumption.

Efficiency in a Food Web
Any assessment of world food resources depends on the level of consumer being targeted. Let us use humans as an example. Many people can be fed if wheat is eaten directly. However, if the grain is first fed to cattle (herbivores) and then we eat the beef, the yield of available food energy is cut by 90% (810 kg of grain is reduced to 82 kg of meat). Far fewer people can be fed from the same land area.

In terms of energy, only about 10% of the kilocalories (food calories, not heat calories) in plant matter survive from the primary to the secondary trophic level. When humans consume meat instead of grain, there is a further loss of biomass and added inefficiency. More energy is lost to the environment at each progressive step in the food chain. You can see that an omnivorous diet such as that of an average North American and European is quite expensive in terms of biomass and energy.

Food web concepts are becoming politicized as world food issues grow more critical. Today, approximately half of the cultivated acreage in the United States and Canada is planted for animal consumption-beef and dairy cattle, hogs, chickens, and turkeys. Livestock feed includes approximately 80% of the annual corn and non-exported soybean harvest. In addition, some lands cleared of rain forest in Central and South America were converted to pasture to produce beef for export to restaurants, stores, and fast-food outlets in developed countries. Thus, lifestyle decisions and dietary patterns in North America and Europe are perpetuating inefficient food webs, not to mention the destruction of valuable resources, both here and overseas.

Câu 31: According to paragraph 1, which of the following is TRUE about autotrophs?