Passage 25

Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured in microns. Rod shaped bacteria are usually from two to four microns long, while rounded ones are generally one micron in diameter. Thus if you enlarged a bacterium a thousand times, it would be just about the size of a pinhead. An adult human magnified by the same amount would be over a mile (1.6 kilometers) tall.

Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds that bacteria are barely visible as tiny rods or dots. One cannot make out anything of their structure. Using special stains, one can see that some bacteria have attached to them wavy-looking “hairs” called flagella. Others have only one flagellum. The flagella rotate, pushing the bacteria though the water. Many bacteria lack flagella and cannot move about by their own power while others can glide along over surfaces by some little understood mechanism.

From the bacterial point of view, the world is a very different place from what it is to humans. To a bacterium, water is as thick as molasses is to us. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. Bacteria under the microscope, even those with no flagella, often bounce about in the water. This is because they collide with the water molecules and are pushed this way and that. Molecules move so rapidly that within a tenth of a second the molecules around a bacterium have all been replaced by new ones, even bacteria without flagella are thus constantly exposed to a changing environment.

1. Which of the following is the main topic of the passage?

2. Which of the following is the smallest?

3. According to the passage, someone who examines bacteria using only a microscope that magnifies 100 times would see ……….. .

4. The relationship between a bacterium and its flagella is most nearly analogous to which of the following?

5. In paragraph 3, the author compares water to molasses, in order to introduce which of the following topics?

Passage 26

If by “suburb” is meant an urban margin that grows more rapidly than its already developed interior, the process of suburbanization began during the emergence of the industrial city in the second quarter of the nineteenth century. Before that period, the city was a small highly compact cluster in which people moved about on foot and goods were conveyed by horse and cart. But the early factories built in the 1830’s and 1840’s were located along waterways and near railheads at the edges of cities, and housing was needed for the thousands of people drawn by the prospect of employment. In time, the factories were surrounded by proliferating mill towns of apartments and row houses that abutted the older, main cities. As a defense against this encroachment and to enlarge their tax bases, the cities appropriated their industrial neighbors. In 1854, for example, the city of Philadelphia annexed most of Philadelphia County. Similar municipal maneuvers took place in Chicago and in New York. Indeed, most great cities of the United States achieved such status only by incorporating the communities along their borders.

       With the acceleration of industrial growth came acute urban crowding and accompanying social stress conditions that began to approach disastrous proportions when, in 1888, the first commercially successful electric traction line was developed. Within a few years the horse-drawn trolleys were retired and electric streetcar networks crisscrossed and connected every major urban area, fostering a wave of suburbanization that transformed the compact industrial city into a dispersed metropolis. This first phase of mass-scale suburbanization was reinforced by the simultaneous emergence of the urban Middle class whose desires for homeownership in neighborhoods far from the aging inner city were satisfied by the developers of single-family housing tracts.

1.Which of the following is the best title for the passage?

2.The author mentions that areas bordering the cities have grown during periods of ……………. .

3.In paragraph 1, the word “encroachment” refers to which of the following?

4. Which of the following was NOT mentioned in the passage as a factor in nineteenth-century suburbanization?

5. It can be inferred from the passage that after 1890 most people traveled around cities by …………. .

Passage 27

     The most familiar speleothems (from the Greek word spelaion for cave and thema for deposit), the decorative dripstone features found in caves, are stalactites and stalagmites. Stalactites hang downward from the ceiling of the cave and are formed as drop after drop of water slowly trickles through cracks in the cave roof. Stalagmites grow upward from the floor of the cave, generally as a result of water dripping from an overhead stalactite. A column forms when a stalactite and a stalagmite grow until they join. A “curtain” or “drapery” begins to form on an inclined ceiling when drops of water trickle along a slope.

Natural openings on the surface that lead to caves are called sinkholes, or swallow holes. Streams sometimes disappear down these holes and flow through the cavern. Rivers may flow from one mountain to another through a series of caves. Some caverns have sinkholes in their floors. Water often builds up a rim of dripstone around the edge of the hole. Dripping water often contains dissolved minerals as well as acid. These minerals too will be deposited; and they may give rich coloring to the deposits. If minerals in the water change, layers of different colors may be formed.

1. Stalagmites are formed by …………… .

2. What are Sinkholes?

4. Which speleothem grows upward from the floor?

4. An “inclined ceiling” is one which is ………… .

5. Which of the following are NOT caused by dripping water?

6. The information in the passage is most relevant to which field of study?

7.“Curtains” can also be called ……….. .

8.The word speleothem comes from which language?

9.What are stalagmites formed by?

10. Which speleothem hangs from the ceiling of a cave?

Passage 28

Horse owners who plan to breed one or more mares should have a working knowledge of heredity and know how to care for breeding animals and foals. The number of mares bred that actually conceive varies from about 40 to 85 percent, with the average running less than 50 percent. Some mares that do conceive fail to produce living foals. This means that, on average, two mares are kept a whole year to produce one foal, and even then, some foals are disappointments from the standpoint of quality.

By careful selection, breeders throughout history have developed various kinds of horses with a wide variety of characteristics to suit many different needs. The Great Horse of the Middle Ages, for example, was bred for size and strength to carry a heavily armored knight. The massive horses of such breeds are often called “cold blooded.” The Arabs bred lithe desert horses that were small and swift. These animals are often referred to as “hot blooded.” Cross-breeding of hot-blooded horses for certain characteristics produced breeds ranging from riding horses to draft horses.

The Thoroughbred is considered by many to be the highpoint of elegance and fine selective breeding. Many persons mistakenly apply the name Thoroughbred to any purebred horse. But a Thoroughbred is a distinct breed of running horses that traces its ancestry through the male line directly back to three Eastern stallions: the Byerly Turk, the Darley Arabian, and the Godolphin Barb.

For convenience the breeds of horses are often divided into three major groups: (1) ponies, (2) heavy, or draft horses, and (3) light horses.

1.Which of the following is NOT an example of an Eastern stallion?

2.Which of the following was NOT a characteristic of the Great Horse of the Middle Ages?

3.It can be inferred from the passage that cold-blooded and hot-blooded horses were cross-bred for what reason?

4.In paragraph 2, the word “lithe” is similar in meaning to ………. .

5.Which of the following is NOT one of the major divisions of horse breeds?

6.According to the passage, which of the following horses is considered to be the finest purebred?

7.To conceive is to ……… .

8.A foal is a(n) ……….. .

9.The average amount of mares bred which actually conceive is less than what percent?

10.A mare is a(n) ………… .