Questions 1 through 3 refer to the following information.
Until recently, aging has been associated with declining body functions. Decreased heart, kidney, and brain functions were considered a natural part of the aging process. In the last decade, scientists have begun to suspect that this decline is not an unavoidable part of growing old. As more people live longer, one fact has become clear: Different people age at different rates. Why do some people not age as fast as others? A few years ago, the best answer would have been a combination of good luck, good habits, and good genes. But these answers were not entirely accurate. After all, some athletes die young, while some heavy smokers live to old age. The real answer is probably much more complicated. Biological, psychological, and environmental factors all influence what happens to a person as he or she grows older. New studies are concentrating on chemical pathways by which emotions and attitudes affect the body. Feelings such as loneliness and a loss of control over one’s own life may play a very real part in the decline associated with age. This new emphasis in no way denies that physical changes occur as one ages. By fifty years of age, some lung capacity is lost, and blood vessels are narrower. However, significant declines do not occur in the absence of disease or damage.
Questions 4 and 5 refer to the following information and diagram.
Ultraviolet light (UVL) in solar radiation can kill living organisms. However, not much UVL reaches Earth’s surface because the gases oxygen and ozone in the upper atmosphere absorb it. Oxygen absorbs a little UVL and in the process changes to ozone. The ozone then absorbs large amounts of UVL.There is evidence that the ozone in the atmosphere is disappearing, and some scientists believe that pollution may be stopping the reaction that converts oxygen into ozone. This would mean less ozone would be available to stop the UVL from reaching Earth. Overexposure to UVL can lead to skin cancer, cataracts, and weakened immune systems in humans. Increased UVL can also lead to reduced crop yield and disruptions in the marine food chain. Some scientists suggest that the chemical chlorofluorocarbon (CFC)—used in air conditioners, refrigerators, spray cans, and cleaning solutions—may be the main pollutant.
Ultraviolet light (UVL) in solar radiation can kill living organisms. However, not much UVL reaches Earth’s surface because the gases oxygen and ozone in the upper atmosphere absorb it. Oxygen absorbs a little UVL and in the process changes to ozone. The ozone then absorbs large amounts of UVL.
There is evidence that the ozone in the atmosphere is disappearing, and some scientists believe that pollution may be stopping the reaction that converts oxygen into ozone. This would mean less ozone would be available to stop the UVL from reaching Earth. Overexposure to UVL can lead to skin cancer, cataracts, and weakened immune systems in humans. Increased UVL can also lead to reduced crop yield and disruptions in the marine food chain.
Some scientists suggest that the chemical chlorofluorocarbon (CFC)—used in air conditioners, refrigerators, spray cans, and cleaning solutions—may be the main pollutant.
Questions 7 and 8 refer to the following information.
Mining companies often scrape away layers of soil to obtain minerals lying below the earth’s surface. Some companies store the removed soil in a pile. This means that surface soil ends up at the bottom of the pile. When the mineral excavation is completed, the miners return the soil to its original spot. Such mining practices have created problems. Biologists know that certain organisms live at very specific depths in the soil. Many of these organisms recycle nutrients and produce fertilizers for plants. Turning the soil upside down during excavation destroys the environments of these soil organisms, so they soon die. Although companies carefully replace the stored soil in the hole, the organisms have already been killed. Nutrients are no longer recycled, and the land becomes barren.
Questions 9 and 10 refer to the following information.
Nuclear power plants currently provide about 10 percent of the electricity used in the United Sates. As the need for power continues to grow, so do problems connected with nuclear power plants. A growing stock of nuclear wastes is one of the major problems. At present, nuclear power companies are sealing and storing wastes directly on their power plant sites. But they agree that this is just a temporary solution. In the 1970s, plans got underway to reprocess nuclear assemblies so their parts could be used to make more power. Then in 1977 the U.S. government banned the building of reprocessing plants. Political leaders feared that during the shipping and recycling of the nuclear wastes, someone might steal enough radioactive materials to manufacture an atomic bomb. In 1981 the government lifted the ban on reprocessing. Still no companies have built reprocessing plants because they are so expensive.