请jcz2008进来看一下

jcz2008

Botany, the study of plants, occupies a peculiar position in the history
of human knowledge. For many thousands of years it was the one field of
awareness about which humans had anything more than the vaguest of
insights. It is impossible to know today just what our Stone Age
ancestors knew about plants, but form what we can observe of pre-
industrial societies that still exist a detailed learning of plants and
their properties must be extremely ancient. This is logical. Plants are
the basis of the food pyramid for all living things even for other
plants. They have always been enormously important to the welfare of
people not only for food, but also for clothing, weapons, tools, dyes,
medicines, shelter, and a great many other purposes. Tribes living today
in the jungles of the Amazon recognize literally hundreds of plants and
know many properties of each. To them, botany, as such, has no name and
is probably not even recognized as a special branch of “ knowledge” at
all.

jcz2008

Unfortunately, the more industrialized we become the farther away we
move from direct contact with plants, and the less distinct our
knowledge of botany grows. Yet everyone comes unconsciously on an
amazing amount of botanical knowledge, and few people will fail to
recognize a rose, an apple, or an orchid. When our Neolithic ancestors,
living in the Middle East about 10,000 years ago, discovered that
certain grasses could be harvested and their seeds planted for richer
yields the next season the first great step in a new association of
plants and humans was taken. Grains were discovered and from them flowed
the marvel of agriculture: cultivated crops. From then on, humans would
increasingly take their living from the controlled production of a few
plants, rather than getting a little here and a little there from many
varieties that grew wild- and the accumulated knowledge of tens of
thousands of years of experience and intimacy with plants in the wild
would begin to fade away.

jcz2008

33 Plankton浮游生物. / 'plжηktэn; `plжηktэn/
Scattered through the seas of the world are billions of tons of small
plants and animals called plankton. Most of these plants and animals are
too small for the human eye to see. They drift about lazily with the
currents, providing a basic food for many larger animals.
Plankton has been described as the equivalent of the grasses that grow
on the dry land continents, and the comparison is an appropriate one. In
potential food value, however, plankton far outweighs that of the land
grasses. One scientist has estimated that while grasses of the world
produce about 49 billion tons of valuable carbohydrates each year, the
sea’s plankton generates more than twice as much.
Despite its enormous food potential, little effect was made until
recently to farm plankton as we farm grasses on land. Now marine
scientists have at last begun to study this possibility, especially as
the sea’s resources loom even more important as a means of feeding an
expanding world population.
No one yet has seriously suggested that “ plankton-burgers” may soon
become popular around the world. As a possible farmed supplementary food
source, however, plankton is gaining considerable interest among marine
scientists.
One type of plankton that seems to have great harvest possibilities is a
tiny shrimp-like creature called krill. Growing to two or three inches
long, krill provides the major food for the great blue whale, the
largest animal to ever inhabit the Earth. Realizing that this whale may
grow to 100 feet and weigh 150 tons at maturity, it is not surprising
that each one devours more than one ton of krill daily.

jcz2008

34 Raising Oysters
In the oysters were raised in much the same way as dirt farmers raised
tomatoes- by transplanting them. First, farmers selected the oyster bed,
cleared the bottom of old shells and other debris, then scattered clean
shells about. Next, they ”planted” fertilized oyster eggs, which
within two or three weeks hatched into larvae. The larvae drifted until
they attached themselves to the clean shells on the bottom. There they
remained and in time grew into baby oysters called seed or spat. The
spat grew larger by drawing in seawater from which they derived
microscopic particles of food. Before long, farmers gathered the baby
oysters, transplanted them once more into another body of water to
fatten them up.
Until recently the supply of wild oysters and those crudely farmed were
more than enough to satisfy people’s needs. But today the delectable
seafood is no longer available in abundance. The problem has become so
serious that some oyster beds have vanished entirely.

jcz2008

Fortunately, as far back as the early 1900’s marine biologists realized
that if new measures were not taken, oysters would become extinct or at
best a luxury food. So they set up well-equipped hatcheries and went to
work. But they did not have the proper equipment or the skill to handle
the eggs. They did not know when, what, and how to feed the larvae. And
they knew little about the predators that attack and eat baby oysters by
the millions. They failed, but they doggedly kept at it. Finally, in the
1940’s a significant breakthrough was made.
The marine biologists discovered that by raising the temperature of the
water, they could induce oysters to spawn not only in the summer but
also in the fall, winter, and spring. Later they developed a technique
for feeding the larvae and rearing them to spat. Going still further,
they succeeded in breeding new strains that were resistant to diseases,
grew faster and larger, and flourished in water of different salinities
and temperatures. In addition, the cultivated oysters tasted better

jcz2008

35.Oil Refining
An important new industry, oil refining, grew after the Civil war. Crude
oil, or petroleum - a dark, thick ooze from the earth - had been known
for hundreds of years, but little use had ever been made of it. In the
1850’s Samuel M. Kier, a manufacturer in western Pennsylvania, began
collecting the oil from local seepages and refining it into kerosene.
Refining, like smelting, is a process of removing impurities from a raw
material.
Kerosene was used to light lamps. It was a cheap substitute for whale
oil, which was becoming harder to get. Soon there was a large demand
for kerosene. People began to search for new supplies of petroleum.
The first oil well was drilled by E.L. Drake, a retired railroad
conductor. In 1859 he began drilling in Titusville, Pennsylvania. The
whole venture seemed so impractical and foolish that onlookers called it
“ Drake’s Folly”. But when he had drilled down about 70 feet(21
meters), Drake struck oil. His well began to yield 20 barrels of crude
oil a day.

jcz2008

News of Drake’s success brought oil prospectors to the scene. By the
early 1860’s these wildcatters were drilling for “ black gold” all
over western Pennsylvania. The boom rivaled the California gold rush of
1848 in its excitement and Wild West atmosphere. And it brought far more
wealth to the prospectors than any gold rush.
Crude oil could be refined into many products. For some years kerosene
continued to be the principal one. It was sold in grocery stores and
door-to-door. In the 1880’s refiners learned how to make other
petroleum products such as waxes and lubricating oils. Petroleum was not
then used to make gasoline or heating oil.

jcz2008

36.Plate Tectonics and Sea-floor Spreading
The theory of plate tectonics describes the motions of the lithosphere,
the comparatively rigid outer layer of the Earth that includes all the
crust and part of the underlying mantle. The lithosphere(n.[地]岩石圈)is
divided into a few dozen plates of various sizes and shapes, in general
the plates are in motion with respect to one another. A mid-ocean ridge
is a boundary between plates where new lithospheric material is injected
from below. As the plates diverge from a mid-ocean ridge they slide on a
more yielding layer at the base of the lithosphere.
Since the size of the Earth is essentially constant, new lithosphere can
be created at the mid-ocean ridges only if an equal amount of
lithospheric material is consumed elsewhere. The site of this
destruction is another kind of plate boundary: a subduction zone. There
one plate dives under the edge of another and is reincorporated into the
mantle. Both kinds of plate boundary are associated with fault systems,
earthquakes and volcanism, but the kinds of geologic activity observed
at the two boundaries are quite different.

jcz2008

The idea of sea-floor spreading actually preceded the theory of plate
tectonics. In its original version, in the early 1960’s, it described
the creation and destruction of the ocean floor, but it did not specify
rigid lithospheric plates. The hypothesis was substantiated soon
afterward by the discovery that periodic reversals of the Earth’s
magnetic field are recorded in the oceanic crust. As magma rises under
the mid-ocean ridge, ferromagnetic minerals in the magma become
magnetized in the direction of the magma become magnetized in the
direction of the geomagnetic field. When the magma cools and solidifies,
the direction and the polarity of the field are preserved in the
magnetized volcanic rock. Reversals of the field give rise to a series
of magnetic stripes running parallel to the axis of the rift. The
oceanic crust thus serves as a magnetic tape recording of the history of
the geomagnetic field that can be dated independently; the width of the
stripes indicates the rate of the sea-floor spreading.

jcz2008

Icebergs are among nature’s most spectacular creations, and yet most
people have never seen one. A vague air of mystery envelops them. They
come into being ----- somewhere ------in faraway, frigid waters, amid
thunderous noise and splashing turbulence, which in most cases no one
hears or sees. They exist only a short time and then slowly waste away
just as unnoticed.
Objects of sheerest beauty they have been called. Appearing in an
endless variety of shapes, they may be dazzlingly white, or they may be
glassy blue, green or purple, tinted faintly of in darker hues. They are
graceful, stately, inspiring ----- in calm, sunlight seas.
But they are also called frightening and dangerous, and that they are ---
- in the night, in the fog, and in storms. Even in clear weather one is
wise to stay a safe distance away from them. Most of their bulk is
hidden below the water, so their underwater parts may extend out far
beyond the visible top. Also, they may roll over unexpectedly, churning
the waters around them.