2015考研英语作文素材精选 (十二)
考研英语作文是一个考察综合运用语言的部分，需要同学们运用逻辑思维下笔成文，因此，考前看一些意义深远、质量好的文章很有必要。以下是2015考研英语作文备考素材精选，请作参考。2015考研英语作文素材精选 (十二)
41.American black bears
American black bears appear in a variety of colors despite their name. In
the eastern part of their range, most of these brown, red, or even yellow coats.
To the north, the black bear is actually gray or white in color. Even in the
same litter, both brown and black furred bears may be born.
Black bears are the smallest of all American bears, ranging in length from
five to six feet, weighing from three hundred to five hundred pounds Their eyes
and ears are small and their eyesight and hearing are not as good as their sense
of smell.
Like all bears, the black bear is timid, clumsy, and rarely dangerous , but
if attacked, most can climb trees and cover ground at great speeds. When angry
or frightened, it is a formidable enemy.
Black bears feed on leaves, herbs. Fruit, berries, insects, fish, and even
larger animals. One of the most interesting characteristics of bears, including
the black bear, is their winter sleep. Unlike squirrels, woodchucks, and many
other woodland animals, bears do not actually hibernate. Although the bear does
not during the winter moths, sustaining itself from body fat, its temperature
remains almost normal, and it breathes regularly four or five times per
minute.
Most black bears live alone, except during mating season. They prefer to
live in caves, hollow logs, or dense thickets. A little of one to four cubs is
born in January or February after a gestation period of six to nine months, and
they remain with their mother until they are fully grown or about one and a half
years old. Black bears can live as long as thirty years in the wild , and even
longer in game preserves set aside for them.
42.Coal-fired power plants
The invention of the incandescent light bulb by Thomas A. Edison in 1879
created a demand for a cheap, readily available fuel with which to generate
large amounts of electric power. Coal seemed to fit the bill, and it fueled the
earliest power stations. (which were set up at the end of the nineteenth century
by Edison himself). As more power plants were constructed throughout the
country, the reliance on coal increased throughout the country, the reliance on
coal increased. Since the First World War, coal-fired power plants had a
combined in the United States each year. In 1986 such plants had a combined
generating capacity of 289,000 megawatts and consumed 83 percent of the nearly
900 million tons of coal mined in the country that year. Given the uncertainty
in the future growth of the nearly 900 million tons of coal mined in the country
that year. Given the uncertainty in the future growth of nuclear power and in
the supply of oil and natural gas, coal-fired power plants could well provide up
to 70 percent of the electric power in the United States by the end of the
century.
Yet, in spite of the fact that coal has long been a source of electricity
and may remain on for many years(coal represents about 80 percent of United
States fossil-fuel reserves), it has actually never been the most desirable
fossil fuel for power plants. Coal contains less energy per unit of weight than
weight than natural gas or oil; it is difficult to transport, and it is
associated with a host of environmental issues, among them acid rain. Since the
late 1960's problems of emission control and waste disposal have sharply reduced
the appeal of coal-fired power plants. The cost of ameliorating these
environment problems along with the rising cost of building a facility as large
and complex as a coal-fired power plant, have also made such plants less
attractive from a purely economic perspective.
Changes in the technological base of coal-fired power plants could restore
their attractiveness, however. Whereas some of these changes are intended mainly
to increase the productivity of existing plants, completely new technologies for
burning coal cleanly are also being developed.
43.Statistics
There were two widely divergent influences on the early development of
statistical methods. Statistics had a mother who was dedicated to keeping
orderly records of government units (states and statistics come from the same
Latin root status) and a gentlemanly gambling father who relied on mathematics
to increase his skill at playing the odds in games of chance. The influence of
the mother on the offspring, statistics, is represented by counting, measuring,
describing, tabulating, ordering, and the taking of censuses-all of which led to
modern descriptive statistics. From the influence of the father came modern
inferential statistics, which is based squarely on theories of probability.
Describing collections involves tabulating, depicting and describing
collections of data. These data may be quantitative such as measures of height,
intelligence or grade level------variables that are characterized by an
underlying continuum---or the data may represent qualitative variables, such as
sex, college major or personality type. Large masses of data must generally
undergo a process of summarization or reduction before they are comprehensible.
Descriptive statistics is a tool for describing or summarizing or reducing to
comprehensible form the properties of an otherwise unwieldy mass of data.
Inferential statistics is a formalized body of methods for solving another
class of problems that present great of problems characteristically involves
attempts to make predictions using a sample of observations. For example, a
school superintendent wishes to determine the proportion of children in a large
school system who come to school without breakfast, have been vaccinated for
flu, or whatever. Having a little knowledge of statistics, the superintendent
would know that it is unnecessary and inefficient to question each child: the
proportion for the sample of as few as 100 children. Thus , the purpose of
inferential statistics is to predict or estimate characteristics of a population
from a knowledge of the characteristics of only a sample of the population.
44.Obtaining Fresh water from icebergs
The concept of obtaining fresh water from icebergs that are towed to
populated areas and arid regions of the world was once treated as a joke more
appropriate to cartoons than real life. But now it is being considered quite
seriously by many nations, especially since scientists have warned that the
human race will outgrow its fresh water supply faster than it runs out of
food.
Glaciers are a possible source of fresh water that has been overlooked
until recently. Three-quarters of the Earth's fresh water supply is still tied
up in glacial ice, a reservoir of untapped fresh water so immense that it could
sustain all the rivers of the world for 1,000 years. Floating on the oceans
every year are 7,659 trillion metric tons of ice encased in 10000 icebergs that
break away from the polar ice caps, more than ninety percent of them from
Antarctica.
Huge glaciers that stretch over the shallow continental shelf give birth to
icebergs throughout the year. Icebergs are not like sea ice, which is formed
when the sea itself freezes, rather, they are formed entirely on land, breaking
off when glaciers spread over the sea. As they drift away from the polar region,
icebergs sometimes move mysteriously in a direction opposite to the wind, pulled
by subsurface currents. Because they melt more slowly than smaller pieces of
ice, icebergs have been known to drift as far north as 35 degrees south of the
equator in the Atlantic Ocean. To corral them and steer them to parts of the
world where they are needed would not be too difficult.
The difficulty arises in other technical matters, such as the prevention of
rapid melting in warmer climates and the funneling of fresh water to shore in
great volume. But even if the icebergs lost half of their volume in towing, the
water they could provide would be far cheaper than that produced by
desalinization, or removing salt from water.
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