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The transition from forest to treeless tundra on a mountain slope is often a dramatic one. Within a vertical distance of just a few tens of meters, trees disappear as a life-form and are replaced by low shrubs, herbs, and grasses. This rapid zone of transition is called the upper timberline or tree line. In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture.

The upper timberline, like the snow line, is highest in the tropics and lowest in the Polar Regions. It ranges from sea level in the Polar Regions to 4,500 meters in the dry subtropics and 3,500-4,500 meters in the moist tropics. Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline. There are some areas, however, where broadleaf deciduous trees form the timberline. Species of birch, for example, may occur at the timberline in parts of the Himalayas.

At the upper timberline the trees begin to become twisted and deformed. This is particularly true for trees in the middle and upper latitudes, which tend to attaingreater heights on ridges, whereas in the tropics the trees reach their greater heights in the valleys. This is because middle- and upper- latitude timberlines are strongly influenced by the duration and depth of the snow cover. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there. In the tropics, the valleys appear to be more favorable because they are less prone to dry out, they have less frost, and they have deeper soils.

There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role. Too much snow, for example, can smother trees, and avalanches and snow creep can damage or destroy them. Late-lying snow reduces the effective growing season to the point where seedlings cannot establish themselves. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes.Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.

Above the tree line there is a zone that is generally called alpine tundra. Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants. Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas. At this great height, rocks, warmed by the sun, melt small snowdrifts.

The most striking characteristic of the plants of the alpine zone is their low growth form. This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface. In an area where low temperatures are limiting to life, the importance of the additional heat near the surface is crucial. The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. In the equatorial mountains the low growth form is less prevalent.

The deserts, which already occupy approximately a fourth of the Earth’s land surface, have in recent decades been increasing at an alarming pace. The expansion of desert-like conditions into areas where they did not previously exist is called desertification. It has been estimated that an additional one-fourth of the Earth’s land surface is threatened by this process.

Desertification is accomplished primarily through the loss of stabilizing natural vegetation and the subsequent accelerated erosion of the soil by wind and water. In some cases the loose soil is blown completely away, leaving a stony surface. In other cases, the finer particles may be removed, while the sand-sized particles are accumulated to form mobile hills or ridges of sand.

Even in the areas that retain a soil cover, the reduction of vegetation typically results in the loss of the soil’s ability to absorb substantial quantities of water. The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration. Water absorption is greatly reduced; consequently runoff is increased, resulting in accelerated erosion rates. The gradual drying of the soil caused by its diminished ability to absorb water results in the further loss of vegetation, so that a cycle of progressive surface deterioration is established.

In some regions, the increase in desert areas is occurring largely as the result of a trend toward drier climatic conditions. Continued gradual global warming has produced an increase in aridity for some areas over the past few thousand years. The process may be accelerated in subsequent decades if global warming resulting from air pollution seriously increases.

There is little doubt, however, that desertification in most areas results primarily from human activities rather than natural processes. The semiarid lands bordering the deserts exist in a delicate ecological balance and are limited in their potential to adjust to increased environmental pressures. Expanding populations are subjecting the land to increasing pressures to provide them with food and fuel. In wet periods, the land may be able to respond to these stresses. During the dry periods that are common phenomena along the desert margins, though, the pressure on the land is often far in excess of its diminished capacity, and desertification results.

Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing, firewood gathering, and overirrigation. The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion.

The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil. This is usually followed by the drying of the soil and accelerated erosion.

Firewood is the chief fuel used for cooking and heating in many countries. The increased pressures of expanding populations have led to the removal of woody plants so that many cities and towns are surrounded by large areas completely lacking in trees and shrubs. The increasing use of dried animal waste as a substitute fuel has also hurt the soil because this valuable soil conditioner and source of plant nutrients is no longer being returned to the land.

The final major human cause of desertification is soil salinization resulting from overirrigation. Excess water from irrigation sinks down into the water table. If no drainage system exists, the water table rises, bringing dissolved salts to the surface. The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil.

The extreme seriousness of desertification results from the vast areas of land and the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form. In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover-crop planting may make it possible to reverse the present deterioration of the surface.

It should be obvious that cetaceans—whales, porpoises, and dolphins—are mammals. They breathe through lungs, not through gills, and give birth to live young. Their streamlined bodies, the absence of hind legs, and the presence of a fluke and blowhole cannot disguise their affinities with land dwelling mammals. However, unlike the cases of sea otters and pinnipeds (seals, sea lions, and walruses, whose limbs are functional both on land and at sea), it is not easy to envision what the first whales looked like. Extinct but already fully marine cetaceans are known from the fossil record. How was the gap between a walking mammal and a swimming whale bridged? Missing until recently were fossils clearly intermediate, or transitional, between land mammals and cetaceans.

Very exciting discoveries have finally allowed scientists to reconstruct the most likely origins of cetaceans. In 1979, a team looking for fossils in northern Pakistan found what proved to be the oldest fossil whale. The fossil was officially named Pakicetus in honor of the country where the discovery was made. Pakicetus was found embedded in rocks formed from river deposits that were 52 million years old. The river that formed these deposits was actually not far from an ancient ocean known as the Tethys Sea.

The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. The skull is cetacean-like but its jawbones lack the enlarged space that is filled with fat or oil and used for receiving underwater sound in modern whales. Pakicetus probably detected sound through the ear opening as in land mammals. The skull also lacks a blowhole, another cetacean adaptation for diving. Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans. It has been suggested that Pakicetus fed on fish in shallow water and was not yet adapted for life in the open ocean. It probably bred and gave birth on land.

Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. This whale lived around 40 million years ago, 12 million years after Pakicetus. Many incomplete skeletons were found but they included, for the first time in an archaeocyte, a complete hind leg that features a foot with three tiny toes. Such legs would have been far too small to have supported the 50-foot-long Basilosaurus on land. Basilosaurus was undoubtedly a fully marine whale with possibly nonfunctional, or vestigial, hind legs.

An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans (“the walking whale that swam”) lived in the Tethys Sea 49 million years ago. It lived around 3 million years after Pakicetus but 9 million before Basilosaurus. The fossil luckily includes a good portion of the hind legs. The legs were strong and ended in long feet very much like those of a modern pinniped. The legs were certainly functional both on land and at sea. The whale retained a tail and lacked a fluke, the major means of locomotion in modern cetaceans. The structure of the backbone shows, however, that Ambulocetus swam like modern whales by moving the rear portion of its body up and down, even though a fluke was missing. The large hind legs were used for propulsion in water. On land, where it probably bred and gave birth, Ambulocetus may have moved around very much like a modern sea lion. It was undoubtedly a whale that linked life on land with life at sea.

The cinema did not emerge as a form of mass consumption until its technology evolved from the initial “peepshow” format to the point where images were projected on a screen in a darkened theater. In the peepshow format, a film was viewed through a small opening in a machine that was created for that purpose. Thomas Edison’s peepshow device, the Kinetoscope, was introduced to the public in 1894. It was designed for use in Kinetoscope parlors, or arcades, which contained only a few individual machines and permitted only one customer to view a short, 50-foot film at any one time. The first Kinetoscope parlors contained five machines. For the price of 25 cents (or 5 cents per machine), customers moved from machine to machine to watch five different films (or, in the case of famous prizefights, successive rounds of a single fight).

These Kinetoscope arcades were modeled on phonograph parlors, which had proven successful for Edison several years earlier. In the phonograph parlors, customers listened to recordings through individual ear tubes, moving from one machine to the next to hear different recorded speeches or pieces of music. The Kinetoscope parlors functioned in a similar way. Edison was more interested in the sale of Kinetoscopes (for roughly $1,000 apiece) to these parlors than in the films that would be run in them (which cost approximately $10 to $15 each). He refused to develop projection technology, reasoning that if he made and sold projectors, then exhibitors would purchase only one machine-a projector-from him instead of several.

Exhibitors, however, wanted to maximize their profits, which they could do more readily by projecting a handful of films to hundreds of customers at a time (rather than one at a time) and by charging 25 to 50 cents admission. About a year after the opening of the first Kinetoscope parlor in 1894, showmen such as Louis and Auguste Lumiere, Thomas Armat and Charles Francis Jenkins, and Orville and Woodville Latham (with the assistance of Edison’s former assistant, William Dickson) perfected projection devices. These early projection devices were used in vaudeville theaters, legitimate theaters, local town halls, makeshift storefront theaters, fairgrounds, and amusement parks to show films to a mass audience.

With the advent of projection in 1895-1896, motion pictures became the ultimate form of mass consumption. Previously, large audiences had viewed spectacles at the theater, where vaudeville, popular dramas, musical and minstrel shows, classical plays, lectures, and slide-and-lantern shows had been presented to several hundred spectators at a time. But the movies differed significantly from these other forms of entertainment, which depended on either live performance or (in the case of the slide-and-lantern shows) the active involvement of a master of ceremonies who assembled the final program.

Although early exhibitors regularly accompanied movies with live acts, the substance of the movies themselves is mass-produced, prerecorded material that can easily be reproduced by theaters with little or no active participation by the exhibitor. Even though early exhibitors shaped their film programs by mixing films and other entertainments together in whichever way they thought would be most attractive to audiences or by accompanying them with lectures, their creative control remained limited. What audiences came to see was the technological marvel of the movies; the lifelike reproduction of the commonplace motion of trains, of waves striking the shore, and of people walking in the street; and the magic made possible by trick photography and the manipulation of the camera.

With the advent of projection, the viewer’s relationship with the image was no longer private, as it had been with earlier peepshow devices such as the Kinetoscope and the Mutoscope, which was a similar machine that reproduced motion by means of successive images on individual photographic cards instead of on strips of celluloid. It suddenly became public—an experience that the viewer shared with dozens, scores, and even hundreds of others. At the same time, the image that the spectator looked at expanded from the minuscule peepshow dimensions of 1 or 2 inches (in height) to the life-size proportions of 6 or 9 feet.

Architecture is the art and science of designing structures that organize and enclose space for practical and symbolic purposes. Because architecture grows out of human needs and aspirations, it clearly communicates cultural values. Of all the visual arts, architecture affects our lives most directly for it determines the character of the human environment in major ways.

Architecture is a three-dimensional form. It utilizes space, mass, texture, line, light, and color. To be architecture, a building must achieve a working harmony with a variety of elements. Humans instinctively seek structures that will shelter and enhance their way of life. It is the work of architects to create buildings that are not simply constructions but also offer inspiration and delight. Buildings contribute to human life when they provide shelter, enrich space, complement their site, suit the climate, and are economically feasible. The client who pays for the building and defines its function is an important member of the architectural team. The mediocre design of many contemporary buildings can be traced to both clients and architects.

In order for the structure to achieve the size and strength necessary to meet its purpose, architecture employs methods of support that, because they are based on physical laws, have changed little since people first discovered them—even while building materials have changed dramatically. The world’s architectural structures have also been devised in relation to the objective limitations of materials. Structures can be analyzed in terms of how they deal with downward forces created by gravity. They are designed to withstand the forces of compression (pushing together), tension (pulling apart), bending, or a combination of these in different parts of the structure.

Even development in architecture has been the result of major technological changes. Materials and methods of construction are integral parts of the design of architecture structures. In earlier times it was necessary to design structural systems suitable for the materials that were available, such as wood, stone, brick. Today technology has progressed to the point where it is possible to invent new building materials to suit the type of structure desired. Enormous changes in materials and techniques of construction within the last few generations have made it possible to enclose space with much greater ease and speed and with a minimum of material. Progress in this area can be measured by the difference in weight between buildings built now and those of comparable size built one hundred years ago.

Modern architectural forms generally have three separate components comparable to elements of the human body: a supporting skeleton or frame, an outer skin enclosing the interior spaces, and equipment, similar to the body’s vital organs and systems. The equipment includes plumbing, electrical wiring, hot water, and air-conditioning. Of course in early architecture—such as igloos and adobe structures—there was no such equipment, and the skeleton and skin were often one.

Much of the world’s great architecture has been constructed of stone because of its beauty, permanence, and availability. In the past, whole cities grew from the arduous task of cutting and piling stone upon. Some of the world’s finest stone architecture can be seen in the ruins of the ancient Inca city of Machu Picchu high in the eastern Andes Mountains of Peru. The doorways and windows are made possible by placing over the open spaces thick stone beams that support the weight from above. A structural invention had to be made before the physical limitations of stone could be overcome and new architectural forms could be created. That invention was the arch, a curved structure originally made of separate stone or brick segments. The arch was used by the early cultures of the Mediterranean area chiefly for underground drains, but it was the Romans who first developed and used the arch extensively in aboveground structures. Roman builders perfected the semicircular arch made of separate blocks of stone. As a method of spanning space, the arch can support greater weight than a horizontal beam. It works in compression to divert the weight above it out to the sides, where the weight is borne by the vertical elements on either side of the arch. The arch is among the many important structural breakthroughs that have characterized architecture throughout the centuries.

The vast grasslands of the High Plains in the central United States were settled by farmers and ranchers in the 1880s. This region has a semiarid climate, and for 50 years after its settlement, it supported a low-intensity agricultural economy of cattle ranching and wheat farming. In the early twentieth century, however, it was discovered that much of the High Plains was underlain by a huge aquifer (a rock layer containing large quantities of groundwater). This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the region

The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota. Water from rains and melting snows has been accumulating in the Ogallala for the past 30,000 years. Estimates indicate that the aquifer contains enough water to fill Lake Huron, but unfortunately, under the semiarid climatic conditions that presently exist in the region, rates of addition to the aquifer are minimal, amounting to about half a centimeter a year.

The first wells were drilled into the Ogallala during the drought years of the early 1930s. The ensuing rapid expansion of irrigation agriculture, especially from the 1950s onward, transformed the economy of the region. More than 100,000 wells now tap the Ogallala. Modern irrigation devices, each capable of spraying 4.5 million liters of water a day, have produced a landscape dominated by geometric patterns of circular green islands of crops. Ogallala water has enabled the High Plains region to supply significant amounts of the cotton, sorghum, wheat, and corn grown in the United States. In addition, 40 percent of American grain-fed beef cattle are fattened here.

This unprecedented development of a finite groundwater resource with an almost negligible natural recharge rate—that is, virtually no natural water source to replenish the water supply—has caused water tables in the region to fall drastically. In the 1930s, wells encountered plentiful water at a depth of about 15 meters; currently, they must be dug to depths of 45 to 60 meters or more. In places, the water table is declining at a rate of a meter a year, necessitating the periodic deepening of wells and the use of ever-more-powerful pumps. It is estimated that at current withdrawal rates, much of the aquifer will run dry within 40 years. The situation is most critical in Texas, where the climate is driest, the greatest amount of water is being pumped, and the aquifer contains the least water. It is projected that the remaining Ogallala water will, by the year 2030, support only 35 to 40 percent of the irrigated acreage in Texas that is supported in 1980.

The reaction of farmers to the inevitable depletion of the Ogallala varies. Many have been attempting to conserve water by irrigating less frequently or by switching to crops that require less water. Others, however, have adopted the philosophy that it is best to use the water while it is still economically profitable to do so and to concentrate on high-value crops such as cotton. The incentive of the farmers who wish to conserve water is reduced by their knowledge that many of their neighbors are profiting by using great amounts of water, and in the process are drawing down the entire region’s water supplies.

In the face of the upcoming water supply crisis, a number of grandiose schemes have been developed to transport vast quantities of water by canal or pipeline from the Mississippi, the Missouri, or the Arkansas rivers. Unfortunately, the cost of water obtained through any of these schemes would increase pumping costs at least tenfold, making the cost of irrigated agricultural products from the region uncompetitive on the national and international markets. Somewhat more promising have been recent experiments for releasing capillary water (water in the soil) above the water table by injecting compressed air into the ground. Even if this process proves successful, however, it would almost triple water costs. Genetic engineering also may provide a partial solution, as new strains of drought-resistant crops continue to be developed. Whatever the final answer to the water crisis may be, it is evident that within the High Plains, irrigation water will never again be the abundant, inexpensive resource it was during the agricultural boom years of the mid-twentieth century.

Plant communities assemble themselves flexibly, and their particular structure depends on the specific history of the area. Ecologists use the term “succession” to refer to the changes that happen in plant communities and ecosystems over time. The first community in a succession is called a pioneer community, while the long-lived community at the end of succession is called a climax community. Pioneer and successional plant communities are said to change over periods from 1 to 500 years. These changes—in plant numbers and the mix of species—are cumulative. Climax communities themselves change but over periods of time greater than about 500 years.

An ecologist who studies a pond today may well find it relatively unchanged in a year’s time. Individual fish may be replaced, but the number of fish will tend to be the same from one year to the next. We can say that the properties of an ecosystem are more stable than the individual organisms that compose the ecosystem.

At one time, ecologists believed that species diversity made ecosystems stable. They believed that the greater the diversity the more stable the ecosystem. Support for this idea came from the observation that long-lasting climax communities usually have more complex food webs and more species diversity than pioneer communities. Ecologists concluded that the apparent stability of climax ecosystems depended on their complexity. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop. In contrast, a complex climax community, such as a temperate forest, will tolerate considerable damage from weather to pests.

The question of ecosystem stability is complicated, however. The first problem is that ecologists do not all agree what “stability” means. Stability can be defined as simply lack of change. In that case, the climax community would be considered the most stable, since, by definition, it changes the least over time. Alternatively, stability can be defined as the speed with which an ecosystem returns to a particular form following a major disturbance, such as a fire. This kind of stability is also called resilience. In that case, climax communities would be the most fragile and the least stable, since they can require hundreds of years to return to the climax state.

Even the kind of stability defined as simple lack of change is not always associated with maximum diversity. At least in temperate zones, maximum diversity is often found in mid-successional stages, not in the climax community. Once a redwood forest matures, for example, the kinds of species and the number of individuals growing on the forest floor are reduced. In general, diversity, by itself, does not ensure stability. Mathematical models of ecosystems likewise suggest that diversity does not guarantee ecosystem stability—just the opposite, in fact. A more complicated system is, in general, more likely than a simple system to break down. A fifteen-speed racing bicycle is more likely to break down than a child’s tricycle.

Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans. We need to know what aspects of a community are most important to the community’s resistance to destruction, as well as its recovery.

Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform. A local population that goes extinct is quickly replaced by immigrants from an adjacent community. Even if the new population is of a different species, it can approximately fill the niche vacated by the extinct population and keep the food web intact.

Two species of deer have been prevalent in the Puget Sound area of Washington State in the Pacific Northwest of the United States. The black-tailed deer, a lowland, west-side cousin of the mule deer of eastern Washington, is now the most common. The other species, the Columbian white-tailed deer, in earlier times was common in the open prairie country; it is now restricted to the low, marshy islands and flood plains along the lower Columbia River.

Nearly any kind of plant of the forest understory can be part of a deer’s diet. Where the forest inhibits the growth of grass and other meadow plants, the black-tailed deer browses on huckleberry, salal, dogwood, and almost any other shrub or herb. But this is fair-weather feeding. What keeps the black-tailed deer alive in the harsher seasons of plant decay and dormancy? One compensation for not hibernating is the built-in urge to migrate. Deer may move from high-elevation browse areas in summer down to the lowland areas in late fall. Even with snow on the ground, the high bushy understory is exposed; also snow and wind bring down leafy branches of cedar, hemlock, red alder, and other arboreal fodder.

The numbers of deer have fluctuated markedly since the entry of Europeans into Puget Sound country. The early explorers and settlers told of abundant deer in the early 1800s and yet almost in the same breath bemoaned the lack of this succulent game animal. Famous explorers of the north American frontier, Lewis and Clark arrived at the mouth of the Columbia River on November 14, 1805, in nearly starved circumstances. They had experienced great difficulty finding game west of the Rockies and not until the second of December did they kill their first elk. To keep 40 people alive that winter, they consumed approximately 150 elk and 20 deer. And when game moved out of the lowlands in early spring, the expedition decided to return east rather than face possible starvation. Later on in the early years of the nineteenth century, when Fort Vancouver became the headquarters of the Hudson’s Bay Company, deer populations continued to fluctuate. David Douglas, Scottish botanical explorer of the 1830s, found a disturbing change in the animal life around the fort during the period between his first visit in 1825 and his final contact with the fort in 1832. A recent Douglas biographer states:” The deer which once picturesquely dotted the meadows around the fort were gone [in 1832], hunted to extermination in order to protect the crops.

Reduction in numbers of game should have boded ill for their survival in later times. A worsening of the plight of deer was to be expected as settlers encroached on the land, logging, burning, and clearing, eventually replacing a wilderness landscape with roads, cities, towns, and factories. No doubt the numbers of deer declined still further. Recall the fate of the Columbian white-tailed deer, now in a protected status. But for the black-tailed deer, human pressure has had just the opposite effect. Wildlife zoologist Helmut Buechner(1953), in reviewing the nature of biotic changes in Washington through recorded time, says that “since the early 1940s, the state has had more deer than at any other time in its history, the winter population fluctuating around approximately 320,000 deer (mule and black-tailed deer), which will yield about 65,000 of either sex and any age annually for an indefinite period.”

The causes of this population rebound are consequences of other human actions. First, the major predators of deer—wolves, cougar, and lynx—have been greatly reduced in numbers. Second, conservation has been insured by limiting times for and types of hunting. But the most profound reason for the restoration of high population numbers has been the fate of the forests. Great tracts of lowland country deforested by logging, fire, or both have become ideal feeding grounds of deer. In addition to finding an increase of suitable browse, like huckleberry and vine maple, Arthur Einarsen, longtime game biologist in the Pacific Northwest, found quality of browse in the open areas to be substantially more nutritive. The protein content of shade-grown vegetation, for example, was much lower than that for plants grown in clearings.

The earliest discovered traces of art are beads and carvings, and then paintings, from sites dating back to the Upper Paleolithic period. We might expect that early artistic efforts would be crude, but the cave paintings of Spain and southern France show a marked degree of skill. So do the naturalistic paintings on slabs of stone excavated in southern Africa. Some of those slabs appear to have been painted as much as 28,000 years ago, which suggests that painting in Africa is as old as painting in Europe. But painting may be even older than that. The early Australians may have painted on the walls of rock shelters and cliff faces at least 30,000 years ago, and maybe as much as 60,000 years ago.

The researchers Peter Ucko and Andree Rosenfeld identified three principallocations of paintings in the caves of western Europe: (1) in obviously inhabited rock shelters and cave entrances; (2) in galleries immediately off the inhabited areas of caves; and (3) in the inner reaches of caves, whose difficulty of access has been interpreted by some as a sign that magical-religious activities were performed there.

The subjects of the paintings are mostly animals. The paintings rest on bare walls, with no backdrops or environmental trappings. Perhaps, like many contemporary peoples, Upper Paleolithic men and women believed that the drawing of a human image could cause death or injury, and if that were indeed their belief, it might explain why human figures are rarely depicted in cave art. Another explanation for the focus on animals might be that these people sought to improve their luck at hunting. This theory is suggested by evidence of chips in the painted figures, perhaps made by spears thrown at the drawings. But if improving their hunting luck was the chief motivation for the paintings, it is difficult to explain why only a few show signs of having been speared. Perhaps the paintings were inspired by the need to increase the supply of animals. Cave art seems to have reached a peak toward the end of the Upper Paleolithic period, when the herds of game were decreasing.

The particular symbolic significance of the cave paintings in southwestern France is more explicitly revealed, perhaps, by the results of a study conducted by researchers Patricia Rice and Ann Paterson. The data they present suggest that the animals portrayed in the cave paintings were mostly the ones that the painters preferred for meat and for materials such as hides. For example, wild cattle (bovines) and horses are portrayed more often than we would expect by chance, probably because they were larger and heavier (meatier) than other animals in the environment. In addition, the paintings mostly portray animals that the painters may have feared the most because of their size, speed, natural weapons such as tusks and horns, and the unpredictability of their behavior. That is, mammoths, bovines, and horses are portrayed more often than deer and reindeer. Thus, the paintings are consistent with the idea that the art is related to the importance of hunting in the economy of Upper Paleolithic people. Consistent with this idea, according to the investigators, is the fact that the art of the cultural period that followed the Upper Paleolithic also seems to reflect how people got their food. But in that period, when getting food no longer depended on hunting large game animals (because they were becoming extinct), the art ceased to focus on portrayals of animals.

Upper Paleolithic art was not confined to cave paintings. Many shafts of spears and similar objects were decorated with figures of animals. The anthropologist Alexander Marshack has an interesting interpretation of some of the engravings made during the Upper Paleolithic. He believes that as far back as 30,000 B.C., hunters may have used a system of notation, engraved on bone and stone, to mark phases of the Moon. If this is true, it would mean that Upper Paleolithic people were capable of complex thought and were consciously aware of their environment. In addition to other artworks, figurines representing the human female in exaggerated form have also been found at Upper Paleolithic sites. It has been suggested that these figurines were an ideal type or an expression of a desire for fertility.

Research has shown that certain minerals are required by plants for normal growth and development. The soil is the source of these minerals, which are absorbed by the plant with the water from the soil. Even nitrogen, which is a gas in its elemental state, is normally absorbed from the soil as nitrate ions. Some soils are notoriously deficient in micro nutrients and are therefore unable to support most plant life. So-called serpentine soils, for example, are deficient in calcium, and only plants able to tolerate low levels of this mineral can survive. In modern agriculture, mineral depletion of soils is a major concern, since harvesting crops interrupts the recycling of nutrients back to the soil.

Mineral deficiencies can often be detected by specific symptoms such as chlorosis (loss of chlorophyll resulting in yellow or white leaf tissue), necrosis (isolated dead patches), anthocyanin formation (development of deep red pigmentation of leaves or stem), stunted growth, and development of woody tissue in an herbaceous plant. Soils are most commonly deficient in nitrogen and phosphorus. Nitrogen-deficient plants exhibit many of the symptoms just described. Leaves develop chlorosis; stems are short and slender, and anthocyanin discoloration occurs on stems, petioles, and lower leaf surfaces. Phosphorus-deficient plants are often stunted, with leaves turning a characteristic dark green, often with the accumulation of anthocyanin. Typically, older leaves are affected first as the phosphorus is mobilized to young growing tissue. Iron deficiency is characterized by chlorosis between veins in young leaves.

Much of the research on nutrient deficiencies is based on growing plants hydroponically, that is, in soilless liquid nutrient solutions. This technique allows researchers to create solutions that selectively omit certain nutrients and then observe the resulting effects on the plants. Hydroponics has applications beyond basic research, since it facilitates the growing of greenhouse vegetables during winter. Aeroponics, a technique in which plants are suspended and the roots misted with a nutrient solution, is another method for growing plants without soil.

While mineral deficiencies can limit the growth of plants, an overabundance of certain minerals can be toxic and can also limit growth. Saline soils, which have high concentrations of sodium chloride and other salts, limit plant growth, and research continues to focus on developing salt-tolerant varieties of agricultural crops. Research has focused on the toxic effects of heavy metals such as lead, cadmium, mercury, and aluminum; however, even copper and zinc, which are essential elements, can become toxic in high concentrations. Although most plants cannot survive in these soils, certain plants have the ability to tolerate high levels of these minerals.

Scientists have known for some time that certain plants, called hyperaccumulators, can concentrate minerals at levels a hundredfold or greater than normal. A survey of known hyperaccumulators identified that 75 percent of them amassed nickel, cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice.Hyperaccumulators run the entire range of the plant world. They may be herbs, shrubs, or trees. Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators. Many are found in tropical and subtropical areas of the world, where accumulation of high concentrations of metals may afford some protection against plant-eating insects and microbial pathogens.

Only recently have investigators considered using these plants to clean up soil and waste sites that have been contaminated by toxic levels of heavy metals–an environmentally friendly approach known as phytoremediation. This scenario begins with the planting of hyperaccumulating species in the target area, such as an abandoned mine or an irrigation pond contaminated by runoff. Toxic minerals would first be absorbed by roots but later relocated to the stem and leaves. A harvest of the shoots would remove the toxic compounds off site to be burned or composted to recover the metal for industrial uses. After several years of cultivation and harvest, the site would be restored at a cost much lower than the price of excavation and reburial, the standard practice for remediation of contaminated soils. For examples, in field trials, the plant alpine pennycress removed zinc and cadmium from soils near a zinc smelter, and Indian mustard, native to Pakistan and India, has been effective in reducing levels of selenium salts by 50 percent in contaminated soils.

The greater Pacific region, traditionally called Oceania, consists of three cultural areas: Melanesia, Micronesia, and Polynesia. Melanesia, in the southwest Pacific, contains the large islands of New Guinea, the Solomons, Vanuatu, and New Caledonia. Micronesia, the area north of Melanesia, consists primarily of small scattered islands. Polynesia is the central Pacific area in the great triangle defined by Hawaii, Easter Island, and New Zealand. Before the arrival of Europeans, the islands in the two largest cultural areas, Polynesia and Micronesia, together contained a population estimated at 700,000.

Speculation on the origin of these Pacific islanders began as soon as outsiders encountered them, in the absence of solid linguistic, archaeological, and biological data, many fanciful and mutually exclusive theories were devised. Pacific islanders are variously thought to have come from North America, South America, Egypt, Israel, and India, as well as Southeast Asia. Many older theories implicitly deprecated the navigational abilities and overall cultural creativity of the Pacific islanders. For example, British anthropologists G. Elliot Smith and W. J. Perry assumed that only Egyptians would have been skilled enough to navigate and colonize the Pacific. They inferred that the Egyptians even crossed the Pacific to found the great civilizations of the New World (North and South America). In 1947 Norwegian adventurer Thor Heyerdahl drifted on a balsa-log raft westward with the winds and currents across the Pacific from South America to prove his theory that Pacific islanders were Native Americans (also called American Indians). Later Heyerdahl suggested that the Pacific was peopled by three migrations: by Native Americans from the Pacific Northwest of North America drifting to Hawaii, by Peruvians drifting to Easter Island, and by Melanesians. In 1969 he crossed the Atlantic in an Egyptian-style reed boat to prove Egyptian influences in the Americas. Contrary to these theorists, the overwhelming evidence of physical anthropology, linguistics, and archaeology shows that the Pacific islanders came from Southeast Asia and were skilled enough as navigators to sail against the prevailing winds and currents.

The basic cultural requirements for the successful colonization of the Pacific islands include the appropriate boat-building, sailing, and navigation skills to get to the islands in the first place, domesticated plants and gardening skills suited to often marginal conditions, and a varied inventory of fishing implements and techniques. It is now generally believed that these prerequisites originated with peoples speaking Austronesian languages (a group of several hundred related languages) and began to emerge in Southeast Asia by about 5000 B.C.E. The culture of that time, based on archaeology and linguistic reconstruction, is assumed to have had a broad inventory of cultivated plants including taro, yarns, banana, sugarcane, breadfruit, coconut, sago, and rice. Just as important, the culture also possessed the basic foundation for an effective maritime adaptation, including outrigger canoes and a variety of fishing techniques that could be effective for overseas voyaging.

Contrary to the arguments of some that much of the pacific was settled by Polynesians accidentally marooned after being lost and adrift, it seems reasonable that this feat was accomplished by deliberate colonization expeditions that set out fully stocked with food and domesticated plants and animals. Detailed studies of the winds and currents using computer simulations suggest that drifting canoes would have been a most unlikely means of colonizing the Pacific. These expeditions were likely driven by population growth and political dynamics on the home islands, as well as the challenge and excitement of exploring unknown waters. Because all Polynesians, Micronesians, and many Melanesians speak Austronesian languages and grow crops derived from Southeast Asia, all these peoples most certainly derived from that region and not the New World or elsewhere. The undisputed pre-Columbian presence in Oceania of the sweet potato, which is a New World domesticate, has sometimes been used to support Heyerdahl’s “American Indians in the Pacific” theories. However, this is one plant out of a long list of Southeast Asian domesticates. As Patrick Kirch, an American anthropologist, points out, rather than being brought by rafting South Americans, sweet potatoes might just have easily been brought back by returning Polynesian navigators who could have reached the west coast of South America.

The geologic timescale is marked by significant geologic and biological events, including the origin of Earth about 4.6 billion years ago, the origin of life about 3.5 billion years ago, the origin of eukaryotic life-forms (living things that have cells with true nuclei) about 1.5 billion years ago, and the origin of animals about 0.6 billion years ago. The last event marks the beginning of the Cambrian period. Animals originated relatively late in the history of Earth—in only the last 10 percent of Earth’s history. During a geologically brief 100-million-year period, all modern animal groups (along with other animals that are now extinct) evolved. This rapid origin and diversification of animals is often referred to as “the Cambrian explosion.”

Scientists have asked important questions about this explosion for more than a century. Why did it occur so late in the history of Earth? The origin of multicellular forms of life seems a relatively simple step compared to the origin of life itself. Why does the fossil record not document the series of evolutionary changes during the evolution of animals? Why did animal life evolve so quickly? Paleontologists continue to search the fossil record for answers to these questions.

One interpretation regarding the absence of fossils during this important 100-million-year period is that early animals were soft bodied and simply did not fossilize. Fossilization of soft-bodied animals is less likely than fossilization of hard-bodied animals, but it does occur. Conditions that promote fossilization of soft-bodied animals include very rapid covering by sediments that create an environment that discourages decomposition. In fact, fossil beds containing soft-bodied animals have been known for many years.

The Ediacara fossil formation, which contains the oldest known animal fossils, consists exclusively of soft-bodied forms. Although named after a site in Australia, the Ediacara formation is worldwide in distribution and dates to Precambrian times. This 700-million-year-old formation gives few clues to the origins of modern animals, however, because paleontologists believe it represents an evolutionary experiment that failed. It contains no ancestors of modern animal groups.

A slightly younger fossil formation containing animal remains is the Tommotian formation, named after a locale in Russia. It dates to the very early Cambrian period, and it also contains only soft-bodied forms. At one time, the animals present in these fossil beds were assigned to various modern animal groups, but most paleontologists now agree that all Tommotian fossils represent unique body forms that arose in the early Cambrian period and disappeared before the end of the period, leaving no descendants in modern animal groups.

A third fossil formation containing both soft-bodied and hard-bodied animals provides evidence of the result of the Cambrian explosion. This fossil formation, called the Burgess Shale, is in Yoho National Park in the Canadian Rocky Mountains of British Columbia. Shortly after the Cambrian explosion, mud slides rapidly buried thousands of marine animals under conditions that favored fossilization. These fossil beds provide evidence of about 32 modern animal groups, plus about 20 other animal body forms that are so different from any modern animals that they cannot be assigned to any one of the modern groups. These unassignable animals include a large swimming predator called Anomalocaris and a soft-bodied animal called Wiwaxia, which ate detritus or algae. The Burgess Shale formation also has fossils of many extinct representatives of modern animal groups. For example, a well-known Burgess Shale animal called Sidneyia is a representative of a previously unknown group of arthropods (a category of animals that includes insects, spiders, mites, and crabs).

Fossil formations like the Burgess Shale show that evolution cannot always be thought of as a slow progression. The Cambrian explosion involved rapid evolutionary diversification, followed by the extinction of many unique animals. Why was this evolution so rapid? No one really knows. Many zoologists believe that it was because so many ecological niches were available with virtually no competition from existing species. Will zoologists ever know the evolutionary sequences in the Cambrian explosion? Perhaps another ancient fossil bed of soft-bodied animals from 600-million-year-old seas is awaiting discovery.

In Britain one of the most dramatic changes of the Industrial Revolution was the harnessing of power. Until the reign of George Ⅲ(1760-1820), available sources of power for work and travel had not increased since the Middle Ages. There were three sources of power: animal or human muscles; the wind, operating on sail or windmill; and running water. Only the last of these was suited at all to the continuous operating of machines, and although waterpower abounded in Lancashire and Scotland and ran grain mills as well as textile mills, it had one great disadvantage: streams flowed where nature intended them to, and water-driven factories had to be located on their banks whether or not the location was desirable for other reasons. Furthermore, even the most reliable waterpower varied with the seasons and disappeared in a drought. The new age of machinery, in short, could not have been born without a new source of both movable and constant power.

The source had long been known but not exploited. Early in the eighteenth century, a pump had come into use in which expanding steam raised a piston in a cylinder, and atmospheric pressure brought it down again when the steam condensed inside the cylinder to form a vacuum. This “atmospheric engine,” invented by Thomas Savery and vastly improved by his partner, Thomas Newcomen, embodied revolutionary principles, but it was so slow and wasteful of fuel that it could not be employed outside the coal mines for which it had been designed. In the 1760s, James Watt perfected a separate condenser for the steam, so that the cylinder did not have to be cooled at every stroke; then he devised a way to make the piston turn a wheel and thus convert reciprocating (back and forth) motion into rotary motion. He thereby transformed an inefficient pump of limited use into a steam engine of a thousand uses. The final step came when steam was introduced into the cylinder to drive the piston backward as well as forward, thereby increasing the speed of the engine and cutting its fuel consumption.

Watt’s steam engine soon showed what it could do. It liberated industry from dependence on running water. The engine eliminated water in the mines by driving efficient pumps, which made possible deeper and deeper mining. The ready availability of coal inspired William Murdoch during the 1790s to develop the first new form of nighttime illumination to be discovered in a millennium and a half. Coal gas rivaled smoky oil lamps and flickering candles, and early in the new century, well-to-do Londoners grew accustomed to gaslit houses and even streets. Iron manufacturers, which had starved for fuel while depending on charcoal, also benefited from ever-increasing supplies of coal: blast furnaces with steam-powered bellows turned out more iron and steel for the new machinery. Steam became the motive force of the Industrial Revolution as coal and iron ore were the raw materials.

By 1800 more than a thousand steam engines were in use in the British Isles, and Britain retained a virtual monopoly on steam engine production until the 1830s. Steam power did not merely spin cotton and roll iron; early in the new century, it also multiplied ten times over the amount of paper that a single worker could produce in a day. At the same time, operators of the first printing presses run by steam rather than by hand found it possible to produce a thousand pages in an hour rather than thirty. Steam also promised to eliminate a transportation problem not fully solved by either canal boats or turnpikes. Boats could carry heavy weights, but canals could not cross hilly terrain; turnpikes could cross the hills, but the roadbeds could not stand up under great weights. These problems needed still another solution, and the ingredients for it lay close at hand. In some industrial regions, heavily laden wagons, with flanged wheels, were being hauled by horses along metal rails; and the stationary steam engine was puffing in the factory and mine. Another generation passed before inventors succeeded in combining these ingredients, by putting the engine on wheels and the wheels on the rails, so as to provide a machine to take the place of the horse. Thus the railroad age sprang from what had already happened in the eighteenth century.

In 1769 in a little town in Oxfordshire, England, a child with the very ordinary name of William Smith was born into the poor family of a village blacksmith. He received rudimentary village schooling, but mostly he roamed his uncle’s farm collecting the fossils that were so abundant in the rocks of the Cotswold hills. When he grew older, William Smith taught himself surveying from books he bought with his small savings, and at the age of eighteen he was apprenticed to a surveyor of the local parish. He then proceeded to teach himself geology, and when he was twenty-four, he went to work for the company that was excavating the Somerset Coal Canal in the south of England.

This was before the steam locomotive, and canal building was at its height. The companies building the canals to transport coal needed surveyors to help them find the coal deposits worth mining as well as to determine the best courses for the canals. This job gave Smith an opportunity to study the fresh rock outcrops created by the newly dug canal. He later worked on similar jobs across the length and breadth of England, all the while studying the newly revealed strata and collecting all the fossils he could find. Smith used mail coaches to travel as much as 10,000 miles per year. In 1815 he published the first modern geological map, “A Map of the Strata of England and Wales with a Part of Scotland,” a map so meticulouslyresearched that it can still be used today.

In 1831 when Smith was finally recognized by the Geological Society of London as the “father of English geology,” it was not only for his maps but also for something even more important. Ever since people had begun to catalog the strata in particular outcrops, there had been the hope that these could somehow be used to calculate geological time. But as more and more accumulations of strata were cataloged in more and more places, it became clear that the sequences of rocks sometimes differed from region to region and that no rock type was ever going to become a reliable time marker throughout the world. Even without the problem of regional differences, rocks present a difficulty as unique time markers. Quartz is quartz—a silicon ion surrounded by four oxygen ions—there’s no difference at all between two-million-year-old Pleistocene quartz and Cambrian quartz created over 500 million years ago.

As he collected fossils from strata throughout England, Smith began to see that the fossils told a different story from the rocks. Particularly in the younger strata, the rocks were often so similar that he had trouble distinguishing the strata, but he never had trouble telling the fossils apart. While rock between two consistent strata might in one place be shale and in another sandstone, the fossils in that shale or sandstone were always the same. Some fossils endured through so many millions of years that they appear in many strata, but others occur only in a few strata, and a few species had their births and extinctions within one particular stratum. Fossils are thus identifying markers for particular periods in Earth’s history.

Not only could Smith identify rock strata by the fossils they contained, he could also see a pattern emerging: certain fossils always appear in more ancient sediments, while others begin to be seen as the strata become more recent. By following the fossils, Smith was able to put all the strata of England’s earth into relative temporal sequence. About the same time, Georges Cuvier made the same discovery while studying the rocks around Paris.Soon it was realized that this principle of faunal (animal) succession was valid not only in England or France but virtually everywhere. It was actually a principle of floral succession as well, because plants showed the same transformation through time as did fauna. Limestone may be found in the Cambrian or—300 million years later—in the Jurassic strata, but a trilobite—the ubiquitous marine arthropod that had its birth in the Cambrian—will never be found in Jurassic strata, nor a dinosaur in the Cambrian.

What do you remember about your life before you were three? Few people can remember anything that happened to them in their early years. Adults’ memories of the next few years also tend to be scanty. Most people remember only a few events—usually ones that were meaningful and distinctive, such as being hospitalized or a sibling’s birth.

How might this inability to recall early experiences be explained? The sheer passage of time does not account for it; adults have excellent recognition of pictures of people who attended high school with them 35 years earlier. Another seemingly plausible explanation—that infants do not form enduring memories at this point in development—also is incorrect. Children two and a half to three years old remember experiences that occurred in their first year, and eleven month olds remember some events a year later. Nor does the hypothesis that infantile amnesia reflects repression—or holding back—of sexually charged episodes explain the phenomenon. While such repression may occur, people cannot remember ordinary events from the infant and toddler periods either.

Three other explanations seem more promising. One involves physiological changes relevant to memory. Maturation of the frontal lobes of the brain continues throughout early childhood, and this part of the brain may be critical for remembering particular episodes in ways that can be retrieved later. Demonstrations of infants’ and toddlers’ long-term memory have involved their repeating motor activities that they had seen or done earlier, such as reaching in the dark for objects, putting a bottle in a doll’s mouth, or pulling apart two pieces of a toy. The brain’s level of physiological maturation may support these types of memories, but not ones requiring explicit verbal descriptions.

A second explanation involves the influence of the social world on children’s language use. Hearing and telling stories about events may help children store information in ways that will endure into later childhood and adulthood. Through hearing stories with a clear beginning, middle, and ending children may learn to extract the gist of events in ways that they will be able to describe many years later. Consistent with this view, parents and children increasingly engage in discussions of past events when children are about three years old. However, hearing such stories is not sufficient for younger children to form enduring memories. Telling such stories to two year olds does not seem to produce long-lasting verbalizable memories.

A third likely explanation for infantile amnesia involves incompatibilities between the ways in which infants encode information and the ways in which older children and adults retrieve it. Whether people can remember an event depends criticallyon the fit between the way in which they earlier encoded the information and the way in which they later attempt to retrieve it. The better able the person is to reconstruct the perspective from which the material was encoded, the more likely that recall will be successful.

This view is supported by a variety of factors that can create mismatches between very young children’s encoding and older children’s and adults’ retrieval efforts. The world looks very different to a person whose head is only two or three feet above the ground than to one whose head is five or six feet above it. Older children and adults often try to retrieve the names of things they saw, but infants would not have encoded the information verbally. General knowledge of categories of events such as a birthday party or a visit to the doctor’s office helps older individuals encode their experiences, but again, infants and toddlers are unlikely to encode many experiences within such knowledge structures.

These three explanations of infantile amnesia are not mutually exclusive; indeed, they support each other. Physiological immaturity may be part of why infants and toddlers do not form extremely enduring memories, even when they hear stories that promote such remembering in preschoolers. Hearing the stories may lead preschoolers to encode aspects of events that allow them to form memories they can access as adults. Conversely, improved encoding of what they hear may help them better understand and remember stories and thus make the stories more useful for remembering future events. Thus, all three explanations—physiological maturation, hearing and producing stories about past events, and improved encoding of key aspects of events—seem likely to be involved in overcoming infantile amnesia.

In 1970 geologists Kenneth J. Hsu and William B.F. Ryan were collecting research data while aboard the oceanographic research vessel Glomar Challenger. An objective of this particular cruise was to investigate the floor of the Mediterranean and to resolve questions about its geologic history. One question was related to evidence that the invertebrate fauna (animals without spines) of the Mediterranean had changed abruptly about 6 million years ago. Most of the older organisms were nearly wiped out, although a few hardy species survived. A few managed to migrate into the Atlantic. Somewhat later, the migrants returned, bringing new species with them. Why did the near extinction and migrations occur?

Another task for the Glomar Challenger’s scientists was to try to determine the origin of the domelike masses buried deep beneath the Mediterranean seafloor. These structures had been detected years earlier by echo-sounding instruments, but they had never been penetrated in the course of drilling. Were they salt domes such as are common along the United States Gulf Coast, and if so, why should there have been so much solid crystalline salt beneath the floor of the Mediterranean?

With question such as these clearly before them, the scientists aboard the Glomar Challenger processed to the Mediterranean to search for the answers. On August 23, 1970, they recovered a sample. The sample consisted of pebbles of hardened sediment that had once been soft, deep-sea mud, as well as granules of gypsum and fragments of volcanic rock. Not a single pebble was found that might have indicated that the pebbles came from the nearby continent. In the days following, samples of solid gypsum were repeatedly brought on deck as drilling operations penetrated the seafloor. Furthermore, the gypsum was found to possess peculiarities of composition and structure that suggested it had formed on desert flats. Sediment above and below the gypsum layer contained tiny marine fossils, indicating open-ocean conditions. As they drilled into the central and deepest part of the Mediterranean basin, the scientists took solid, shiny, crystalline salt from the core barrel. Interbedded with the salt were thin layers of what appeared to be windblown silt.

The time had come to formulate a hypothesis. The investigators theorized that about 20 million years ago, the Mediterranean was a broad seaway linked to the Atlantic by two narrow straits. Crustal movements closed the straits, and the landlocked Mediterranean began to evaporate. Increasing salinity caused by the evaporation resulted in the extermination of scores of invertebrate species. Only a few organisms especially tolerant of very salty conditions remained. As evaporation continued, the remaining brine (salt water) became so dense that the calcium sulfate of the hard layer was precipitated. In the central deeper part of the basin, the last of the brine evaporated to precipitate more soluble sodium chloride (salt). Later, under the weight of overlying sediments, this salt flowed plastically upward to form salt domes. Before this happened, however, the Mediterranean was a vast desert 3,000 meters deep. Then, about 5.5 million years ago came the deluge. As a result of crustal adjustments and faulting, the Strait of Gibraltar, where the Mediterranean now connects to the Atlantic, opened, and water cascaded spectacularly back into the Mediterranean. Turbulent waters tore into the hardened salt flats, broke them up, and ground them into the pebbles observed in the first sample taken by the Challenger. As the basin was refilled, normal marine organisms returned. Soon layer of oceanic ooze began to accumulate above the old hard layer.The salt and gypsum, the faunal changes, and the unusual gravel provided abundant evidence that the Mediterranean was once a desert.

There is a quality of cohesiveness about the Roman world that applied neither to Greece nor perhaps to any other civilization, ancient or modern. Like the stone of Roman wall, which were held together both by the regularity of the design and by that peculiarly powerful Roman cement, so the various parts of the Roman realm were bonded into a massive, monolithic entity by physical, organizational, and psychological controls. The physical bonds included the network of military garrisons, which were stationed in every province, and the network of stone-built roads that linked the provinces with Rome. The organizational bonds were based on the common principles of law and administration and on the universal army of officials who enforced common standards of conduct. The psychological controls were built on fear and punishment—on the absolute certainty that anyone or anything that threatened the authority of Rome would be utterly destroyed.

The source of Roman obsession with unity and cohesion may well have lain in the pattern of Rome’s early development. Whereas Greece had grown from scores of scattered cities, Rome grew from one single organism. While the Greek world had expanded along the Mediterranean seas lanes, the Roman world was assembled by territorial conquest. Of course, the contrast is not quite so stark: in Alexander the Great the Greeks had found the greatest territorial conqueror of all time; and the Romans, once they moved outside Italy, did not fail to learn the lessons of sea power. Yet the essential difference is undeniable. The key to the Greek world lay in its high-powered ships; the key to Roman power lay in its marching legions. The Greeks were wedded to the sea; the Romans, to the land. The Greek was a sailor at heart; the Roman, a landsman.

Certainly, in trying to explain the Roman phenomenon, one would have to place great emphasis on this almost instinct for the territorial imperative. Roman priorities lay in the organization, exploitation, and defense of their territory. In all probability it was the fertile plain of Latium, where the Latins who founded Rome originated, that created the habits and skills of landed settlement, landed property, landed economy, landed administration, and a land-based society. From this arose the Roman genius for military organization and orderly government. In turn, a deep attachment to the land, and to the stability which rural life engenders, fostered the Roman virtues: gravitas, a sense of responsibility, pietas, a sense of devotion to family and country, and iustitia, a sense of the natural order.

Modern attitudes to Roman civilization range from the infinitely impressed to the thoroughly disgusted. As always, there are the power worshippers, especially among historians, who are predisposed to admire whatever is strong, who feel more attracted to the might of Rome than to the subtlety of Greece. At the same time, there is a solid body of opinion that dislikes Rome. For many, Rome is at best the imitator and the continuator of Greece on a larger scale. Greek civilization had quality; Rome, mere quantity. Greece was original; Rome, derivative. Greece had style; Rome had money. Greece was the inventor; Rome, the research and development division. Such indeed was the opinion of some of the more intellectual Romans. “Had the Greeks held novelty in such disdain as we,” asked Horace in his epistle, “what work of ancient date would now exist?”

Rome’s debt to Greece was enormous. The Romans adopted Greek religion and moral philosophy. In literature, Greek writers were consciously used as models by their Latin successors. It was absolutely accepted that an educated Roman should be fluent in Greek. In speculative philosophy and the sciences, the Romans made virtually no advance on early achievements.

Yet it would be wrong to suggest that Rome was somehow a junior partner in Greco-Roman civilization. The Roman genius was projected into new spheres—especially into those of law, military organization, administration, and engineering. Moreover, the tensions that arose within the Roman state produced literary and artistic sensibilities of the highest order. It was no accident that many leading Roman soldiers and statesmen were writers of high caliber.

There is evidence of agriculture in Africa prior to 3000 B.C. It may have developed independently, but many scholars believe that the spread of agriculture and iron throughout Africa linked it to the major centers of the Near East and Mediterranean world. The drying up of what is now the Sahara desert had pushed many peoples to the south into sub-Sahara Africa. These peoples settled at first in scattered hunting-and-gathering bands, although in some places near lakes and rivers, people who fished, with a more secure food supply, lived in larger population concentrations. Agriculture seems to have reached these people from the Near East, since the first domesticated crops were millets and sorghums whose origins are not African but west Asian. Once the idea of planting diffused, Africans began to develop their own crops, such as certain varieties of rice, and they demonstrated a continued receptiveness to new imports. The proposed areas of the domestication of African crops lie in a band that extends from Ethiopia across southern Sudan to West Africa. Subsequently, other crops, such as bananas, were introduced from Southeast Asia.

Livestock also came from outside Africa. Cattle were introduced from Asia, as probably were domestic sheep and goats. Horses were apparently introduced by the Hyksos invaders of Egypt (1780-1560 B.C.) and then spread across the Sudan to West Africa. Rock paintings in the Sahara indicate that horses and chariots were used to traverse the desert and that by 300-200 B.C., there were trade routes across the Sahara. Horses were adopted by peoples of the West African savannah, and later their powerful cavalry forces allowed them to carve out large empires. Finally, the camel was introduced around the first century A.D. This was an important innovation, because the camel’s abilities to thrive in harsh desert conditions and to carry large loads cheaply made it an effective and efficient means of transportation. The camel transformed the desert from a barrier into a still difficult, but more accessible, route of trade and communication.

Iron came from West Asia, although its routes of diffusion were somewhat different than those of agriculture. Most of Africa presents a curious case in which societies moved directly from a technology of stone to iron without passing through the intermediate stage of copper or bronze metallurgy, although some early copper-working sites have been found in West Africa. Knowledge of iron making penetrated into the forest and savannahs of West Africa at roughly the same time that iron making was reaching Europe. Evidence of iron making has been found in Nigeria, Ghana, and Mali.

This technological shift cause profound changes in the complexity of African societies. Iron represented power. In West Africa the blacksmith who made tools and weapons had an important place in society, often with special religious powers and functions. Iron hoes, which made the land more productive, and iron weapons, which made the warrior more powerful, had symbolic meaning in a number of West Africa societies. Those who knew the secrets of making iron gained ritual and sometimes political power.

Unlike in the Americas, where metallurgy was a very late and limited development, Africans had iron from a relatively early date, developing ingenious furnaces to produce the high heat needed for production and to control the amount of air that reached the carbon and iron ore necessary for making iron. Much of Africa moved right into the Iron Age, taking the basic technology and adapting it to local conditions and resources.

The diffusion of agriculture and later of iron was accompanied by a great movement of people who may have carried these innovations. These people probably originated in eastern Nigeria. Their migration may have been set in motion by an increase in population caused by a movement of peoples fleeing the desiccation, or drying up, of the Sahara. They spoke a language, proto-Bantu (“Bantu” means “the people”), which is the parent tongue of a language of a large number of Bantu languages still spoken throughout sub-Sahara Africa. Why and how these people spread out into central and southern Africa remains a mystery, but archaeologists believe that their iron weapons allowed them to conquer their hunting-gathering opponents, who still used stone implements. Still, the process is uncertain, and peaceful migration—or simply rapid demographic growth—may have also caused the Bantu explosion.

Response

I disagree with the claim that it is no longer possible for a society to regard any living man or woman as a hero solely because the reputation of anyone subjected to media scrutiny will eventually be diminished. While media scrutiny can certainly impact public perception, the concept of heroism is multifaceted and can withstand the challenges posed by modern media.

Firstly, it’s important to recognize that heroism is not solely based on flawless, unblemished reputations. Heroes are often admired for their actions, values, and the positive impact they have on society, rather than for being perfect individuals. Even historical heroes faced controversies and imperfections, but their contributions and virtues were deemed more significant.

Secondly, media scrutiny does not necessarily diminish heroism; it can also uncover and highlight heroic acts and qualities. The media has the power to shed light on the actions of individuals who selflessly help others, overcome adversity, or champion noble causes. Such individuals can become heroes precisely because their stories are shared through media outlets, inspiring others to emulate their actions.

Furthermore, society has the capacity to differentiate between private flaws and public heroism. While media scrutiny may reveal personal missteps or mistakes, people often consider the broader context and impact of an individual’s actions when assessing heroism. For instance, a public figure who has made personal mistakes can still be regarded as a hero if their contributions to society or their resilience in the face of adversity are seen as heroic.

It’s also important to acknowledge that the perception of heroism can vary among individuals and communities. What one group views as heroic, another may not. This diversity of perspectives allows for a wide range of heroes to emerge, each resonating with different segments of society.

While the reason suggests that media scrutiny will inevitably diminish reputations, it does not account for the ability of individuals to rehabilitate their images, make amends for their mistakes, or continue to perform heroic deeds. People are capable of growth and redemption, and society is often willing to forgive and reevaluate its judgments over time.

In conclusion, the claim that no living individual can be regarded as a hero due to media scrutiny is overly simplistic. Heroism is a complex and multifaceted concept that considers not only personal reputation but also actions, values, and contributions to society. While media scrutiny can present challenges, it does not inherently diminish the potential for individuals to be recognized as heroes. Society’s capacity for forgiveness, nuanced judgment, and recognition of heroic deeds allows for the continued emergence of heroes in the modern age.

Response

I agree with the statement that competition for high grades can seriously limit the quality of learning at all levels of education, but I believe it is important to clarify that it is not competition itself that is the problem but rather the way it is often implemented and emphasized in educational systems.

Competition can be a powerful motivator, encouraging students to strive for excellence and reach their full potential. Healthy competition can foster a sense of achievement and drive for self-improvement. However, the issue arises when the pursuit of high grades becomes the sole focus of education, overshadowing the importance of deep, meaningful learning.

One of the ways in which competition for high grades can limit the quality of learning is by promoting surface-level learning. When students are primarily focused on earning the highest marks, they may resort to memorization and rote learning to meet grading criteria, rather than truly understanding and internalizing the subject matter. This approach may allow them to excel on tests and assignments but does not promote critical thinking, problem-solving, or a deep appreciation for the material.

Moreover, excessive competition can create a culture of academic stress and anxiety, which is detrimental to the well-being of students. The pressure to outperform peers and achieve top grades can lead to high levels of stress, sleep deprivation, and mental health issues. In such an environment, the joy of learning is often replaced by the fear of failure.

Additionally, an emphasis on competition can deter collaboration and hinder the development of important life skills such as teamwork, communication, and empathy. When students view their classmates as competitors, they may be less inclined to share knowledge, support one another, or engage in collaborative learning experiences.

However, competition for high grades can also have some positive aspects. It can incentivize hard work and discipline, encouraging students to put in the effort required to master challenging subjects. It can also prepare students for competitive environments they may encounter later in their academic or professional careers.

To mitigate the negative effects of grade-centered competition and enhance the quality of learning, it is crucial for educational institutions to adopt a balanced approach. This includes promoting intrinsic motivation for learning, emphasizing the development of critical thinking skills, and assessing students in ways that go beyond traditional exams and grades. Encouraging a growth mindset, where effort and learning from mistakes are valued, can also help create a healthier learning environment.

In conclusion, while competition for high grades can serve as a motivator, it can also limit the quality of learning when it becomes the sole focus of education. Striking a balance between healthy competition and the promotion of deep, meaningful learning is essential to ensure that students not only achieve high grades but also acquire the skills and knowledge necessary for success in the real world.

Response

I agree with the recommendation that universities should require every student to take a variety of courses outside their field of study. Encouraging students to pursue a well-rounded education by exploring diverse subjects can have several significant advantages.

Firstly, requiring students to take courses outside their field of study promotes intellectual diversity and fosters a more comprehensive education. Exposure to a range of disciplines, from the humanities to the sciences, allows students to develop a broader perspective and a more profound understanding of the interconnectedness of knowledge. This multidisciplinary approach can enhance critical thinking skills and creativity by encouraging students to draw connections between different fields.

Secondly, such a requirement can help students discover new interests and talents they might not have otherwise explored. Many students enter university with a limited understanding of their own passions and aptitudes. By exposing them to various subjects, universities can assist students in identifying previously unknown areas of interest and potential career paths. For example, a student majoring in physics may discover a passion for philosophy or art history through these mandatory courses.

Furthermore, taking courses outside one’s field of study can foster a more well-rounded skill set. For instance, a computer science major who takes courses in literature or ethics may develop better communication skills, ethical reasoning, and a broader cultural understanding, all of which are valuable in a diverse and interconnected world.

However, it’s essential to acknowledge that there are potential challenges and objections to this approach. Some argue that such requirements can extend the time and cost of obtaining a degree, making it more difficult for students to graduate on time or manage their financial commitments. Additionally, there is concern that mandatory courses outside one’s field may divert attention and resources away from core major requirements.

To address these concerns, universities can design their curriculum with flexibility in mind. They can offer a variety of courses that fulfill the requirement, allowing students to choose subjects that align with their interests and career goals. Additionally, universities can explore ways to integrate interdisciplinary learning into major coursework, minimizing the need for separate mandatory courses.

In conclusion, requiring students to take courses outside their field of study can enrich their educational experience, promote intellectual diversity, and help them discover new interests and talents. While there are potential challenges to implementing such requirements, a well-designed curriculum that allows for flexibility and choice can mitigate these concerns. Ultimately, a more well-rounded education benefits both individual students and society as a whole by producing graduates with a broader perspective and a deeper appreciation for the complexities of the world.

Response

I agree with the recommendation that educators should seek input from students regarding the curriculum, but I believe that the process should be more nuanced and balanced. While incorporating student preferences can enhance engagement and relevance, it must be done in a way that maintains educational standards and objectives.

Incorporating student input into the curriculum has several advantages. It can increase student engagement and motivation by allowing them to explore topics they are genuinely interested in. When students have a say in what they learn, they often become more invested in their education. Additionally, it can make the curriculum more relevant to students’ lives and future goals, as they can provide insights into the skills and knowledge they believe will be valuable.

However, there are limitations to relying solely on student preferences. First, students may not always have a complete understanding of their educational needs. They may prioritize subjects that seem interesting in the short term but overlook foundational knowledge or essential skills that are necessary for their academic and professional development. Educators have the expertise to design a curriculum that balances immediate interests with long-term educational goals.

Second, curricular decisions should align with educational standards and objectives. In many cases, there are specific skills and knowledge areas that students need to master to meet these standards and be prepared for future academic or career challenges. Curriculum development should be guided by these standards to ensure that students receive a well-rounded and comprehensive education.

Furthermore, curricular decisions should consider the diverse needs and backgrounds of students. While it’s essential to incorporate student preferences, educators must also address the needs of the entire student body and ensure that the curriculum is inclusive and equitable. Student preferences alone may not account for the varying educational requirements of all students.

To strike a balance, educators can employ a consultative approach. They can seek input from students about their interests and preferences and incorporate this feedback into the curriculum development process. However, educators should also use their expertise to design a curriculum that meets educational standards and objectives, providing a well-rounded education that prepares students for future challenges.

In conclusion, incorporating student input into the curriculum is valuable for increasing engagement and relevance. However, it should be done in a balanced manner that considers educational standards and objectives, as well as the diverse needs of students. By combining student preferences with educational expertise, educators can create a curriculum that is both engaging and rigorous, ultimately benefiting students and society as a whole.

Response

I agree with the recommendation that educators should teach facts only after their students have studied the ideas, trends, and concepts that help explain those facts. This approach, often referred to as a “conceptual framework” or “inquiry-based learning,” offers several advantages for students’ understanding and retention of information.

When students are introduced to concepts and ideas before being presented with facts, they are more likely to engage in critical thinking and active learning. Rather than passively memorizing isolated facts, students are encouraged to explore the underlying principles and connections between pieces of information. This approach fosters a deeper and more meaningful understanding of the subject matter.

Moreover, teaching concepts and ideas before facts can promote a more holistic view of the subject. Students gain a broader context and can better appreciate the relevance and significance of the facts they encounter. This approach encourages students to ask questions, make connections, and explore the subject matter in a more comprehensive manner.

For example, in a history class, educators might first introduce the concepts of imperialism, nationalism, and colonialism before delving into specific historical events. By understanding these overarching ideas, students can better analyze and interpret the facts related to specific historical periods, making their learning more coherent and insightful.

However, there are instances where teaching facts before concepts may be advantageous. In subjects that require a foundational knowledge of facts to build upon, such as mathematics or certain sciences, introducing facts early can provide a necessary scaffold for more advanced learning. Learning multiplication tables, for instance, is essential before moving on to more complex mathematical concepts.

Furthermore, the timing of when to introduce facts may also depend on the developmental stage of the students. Younger learners, for instance, may benefit from a more fact-based approach to build foundational knowledge and then gradually transition to a more concept-driven approach as they advance in their education.

In conclusion, teaching concepts and ideas before facts is a valuable pedagogical approach that promotes critical thinking, deep understanding, and a broader context for learning. While there may be circumstances where teaching facts early is appropriate, adopting a conceptual framework as a foundational approach can enhance the overall quality of education by encouraging students to engage with the subject matter more deeply and meaningfully.

Response

I disagree with the claim that we can usually learn much more from people whose views we share than from those whose views contradict our own. While there is value in learning from like-minded individuals, the notion that disagreement always causes stress and inhibits learning is overly simplistic.

Firstly, learning from people who share our views can be comfortable and affirming, but it often leads to confirmation bias, where we only seek information that supports our existing beliefs. This can limit intellectual growth and critical thinking. In contrast, engaging with individuals who hold opposing views challenges us to reconsider our perspectives, question assumptions, and deepen our understanding. Disagreement, when approached constructively, can lead to more robust and well-rounded knowledge.

Secondly, diverse viewpoints are essential for innovation and progress. In fields like science, technology, and social sciences, breakthroughs often result from the clash of differing ideas. When individuals with different perspectives collaborate and engage in healthy debate, they can collectively arrive at more comprehensive and innovative solutions to complex problems. Disagreement fosters creativity and drives intellectual exploration.

Moreover, the claim overlooks the importance of emotional intelligence and effective communication in handling disagreements. While it is true that poorly managed disagreements can cause stress and inhibit learning, individuals can develop skills to engage in respectful and constructive discourse. Learning to navigate differences of opinion with empathy and open-mindedness can lead to personal growth and the acquisition of new insights.

It’s also worth noting that not all disagreements are equal in terms of their impact on stress levels and learning. Civil, well-informed debates can be stimulating and intellectually rewarding, while hostile or unproductive arguments are more likely to lead to stress and inhibit learning. It is the manner in which disagreements are approached that largely determines their effect.

In conclusion, while learning from like-minded individuals can be valuable, the claim that we usually learn much more from those who share our views than from those who hold opposing views is overly simplistic. Disagreement, when managed constructively and respectfully, is a valuable catalyst for intellectual growth, innovation, and the development of critical thinking skills. The key is to foster a culture of healthy debate and open-mindedness to fully harness the learning potential of diverse viewpoints.

Response

I disagree with the recommendation that government officials should rely solely on their own judgment rather than unquestioningly carrying out the will of the people they serve. While government officials should exercise their expertise and judgment, they are elected or appointed to represent the interests and preferences of the citizens. A balance between their judgment and the will of the people is crucial for a functioning democracy.

There are instances where officials should exercise their own judgment. They bring expertise and experience to the table, which can be valuable when making complex decisions. For example, in matters of national security, economic policy, or public health, officials may need to rely on their knowledge and analysis to make informed choices that may not align with popular opinion.

However, it is equally important to consider the circumstances where disregarding the will of the people can be disadvantageous. Democracy is founded on the principle of government by the people and for the people. Public officials are accountable to the electorate and should respect the values and preferences of their constituents.

Disregarding the will of the people can lead to a disconnect between the government and the governed. When officials consistently act against the wishes of the majority, it can erode trust in government and the democratic process itself. Citizens may become disengaged and disillusioned, leading to a breakdown of the social contract.

Moreover, there are mechanisms in democratic systems, such as elections and public input, that allow for the expression of the people’s will. Ignoring these mechanisms undermines the democratic foundations of a society. Government officials should be responsive to the changing needs and desires of the population, and their judgment should be informed by a deep understanding of the public’s concerns.

In circumstances where officials believe that the will of the people conflicts with what they perceive as the greater good or the long-term interests of the nation, they should engage in open dialogue and persuasion rather than outright disregard. Public officials have a responsibility to communicate their rationale and engage in a constructive debate that respects democratic principles.

In conclusion, government officials should not rely solely on their own judgment to the detriment of the will of the people they serve. A balance between their expertise and the preferences of the electorate is essential for a healthy democracy. While there are situations where officials must make difficult decisions, they should do so with transparency, accountability, and a commitment to preserving the democratic principles that underpin their roles in government.

Response

I agree with the recommendation that young people should be encouraged to pursue long-term, realistic goals rather than seeking immediate fame and recognition. While the desire for fame and recognition is not inherently negative, it’s essential to prioritize goals that are sustainable and contribute to personal growth and societal well-being.

Encouraging young people to focus on long-term, realistic goals has several advantages. Firstly, it promotes patience and resilience. Achieving meaningful and lasting success often requires sustained effort, dedication, and the ability to weather setbacks and failures along the way. Pursuing immediate fame can lead to frustration and disappointment when quick success does not materialize.

Secondly, long-term goals tend to be more personally fulfilling and satisfying. They provide a sense of purpose and direction in life, allowing individuals to make meaningful contributions to their communities and society as a whole. In contrast, seeking immediate fame may lead to shallow or superficial achievements that do not bring lasting happiness.

Moreover, pursuing realistic long-term goals encourages personal development and skill acquisition. It necessitates the acquisition of knowledge, the development of expertise, and the cultivation of a strong work ethic. These qualities are essential for long-term success and are transferable to various aspects of life.

However, it’s important to acknowledge that there are situations where the pursuit of immediate fame and recognition may be advantageous. In the realm of entertainment, for example, aspiring actors, musicians, or social media influencers may benefit from early exposure and recognition. Nevertheless, even in these fields, it is often individuals with long-term dedication and talent development who achieve lasting fame and success.

Additionally, it is crucial to consider the potential downsides of seeking immediate fame, such as the pressure to maintain a public image, the risk of burnout, and the impact on mental health. Pursuing fame for its own sake can lead to a shallow and externally driven life, which may not contribute to overall well-being.

In conclusion, while there may be instances where immediate fame and recognition are appropriate, encouraging young people to prioritize long-term, realistic goals is generally more advantageous. This approach fosters patience, resilience, personal growth, and a sense of purpose. It enables individuals to make meaningful contributions to their own lives and society, ultimately leading to more fulfilling and sustainable success.

Response

I disagree with the recommendation that the best way to teach is to praise positive actions and ignore negative ones exclusively. While positive reinforcement is an effective teaching strategy, it should be complemented by addressing negative actions and providing constructive feedback. A balanced approach to teaching includes both praise for positive actions and guidance for improvement when negative actions occur.

Praising positive actions is essential for several reasons. It boosts students’ confidence and self-esteem, motivating them to continue their efforts. Positive reinforcement acknowledges their accomplishments and encourages a growth mindset, where students believe in their ability to learn and improve. This approach is particularly effective when students demonstrate enthusiasm, creativity, or effort in their work.

However, ignoring negative actions can have detrimental consequences. It can send the message that mistakes and misbehavior are acceptable, potentially leading to a lack of discipline, accountability, and responsibility. It also misses valuable opportunities for teaching and learning.

Addressing negative actions and providing constructive feedback is essential for students’ growth and development. When students make mistakes or exhibit inappropriate behavior, they need guidance to understand why their actions were incorrect and how to correct them. Ignoring these actions may result in recurring problems and hinder their overall progress.

For example, if a student consistently fails to complete assignments or disrupts the classroom, ignoring these negative actions would not help the student or the learning environment. Instead, constructive feedback, discussion, and guidance are necessary to address the underlying issues and provide a path for improvement.

Furthermore, a balanced approach that addresses both positive and negative actions teaches students about responsibility and accountability. It helps them understand that their actions have consequences and that learning from mistakes is a valuable part of the educational process.

In certain circumstances, excessive focus on negative actions can lead to a punitive and demoralizing learning environment, which is not conducive to effective teaching. However, the key is to provide constructive feedback and guidance when addressing negative actions, rather than simply ignoring them.

In conclusion, while praising positive actions is an essential aspect of teaching, ignoring negative actions is not conducive to effective education. A balanced approach that includes positive reinforcement and constructive feedback for addressing negative actions is more advantageous. It promotes a healthy learning environment, motivates students to learn from their mistakes, and helps them develop the skills and character traits necessary for success in both education and life.

Response

I agree with the recommendation that all college students should be required to take courses in which they read poetry, novels, mythology, and other types of imaginative literature. Such courses offer several advantages that contribute to the well-rounded development of students.

Firstly, courses in imaginative literature foster critical thinking and analytical skills. Analyzing poems, novels, and mythology requires students to delve deep into the text, interpret symbolism, explore themes, and make connections. This type of intellectual engagement hones their ability to think critically, consider multiple perspectives, and construct well-reasoned arguments—a skill set that is valuable in various academic disciplines and professional contexts.

Secondly, these courses promote empathy and an understanding of diverse perspectives. Literature often explores the human experience through different cultures, historical periods, and social contexts. Reading about characters and situations from various backgrounds allows students to develop empathy and gain insights into the lives and struggles of others. This empathetic understanding is essential in fostering a sense of cultural awareness and global citizenship.

Moreover, imaginative literature sparks creativity and imagination. Exposure to different forms of storytelling and literary techniques can inspire students to think creatively and express themselves more effectively. This creative thinking is not limited to the realm of literature but can also benefit students in problem-solving, innovation, and artistic pursuits.

However, it’s essential to acknowledge potential objections to this recommendation. Some argue that college curricula should focus exclusively on practical and career-oriented subjects to ensure graduates are job-ready. While vocational skills are crucial, an exclusive focus on practical education can lead to a one-dimensional, utilitarian approach to learning that neglects the development of well-rounded individuals.

Furthermore, it is important to consider that not all students may have an inherent interest in imaginative literature. Some may argue that forcing students to take such courses could lead to disengagement and a lack of enthusiasm. To address this concern, universities can design these courses to be engaging and relevant to students’ interests and career goals, demonstrating the real-world applicability of literature studies.

In conclusion, requiring college students to take courses in imaginative literature is advantageous for their well-rounded development. These courses enhance critical thinking skills, promote empathy, nurture creativity, and provide a broader cultural and historical perspective. While there are potential objections related to practicality and student interest, these concerns can be addressed through well-designed courses that emphasize the real-world relevance of literature studies.

Response

I disagree with the statement that for any work of art to have merit, it must be understandable to most people. Art is a deeply subjective and diverse form of expression, and its value and meaning can vary greatly from person to person. While some art may resonate with a broad audience, the idea that all art must be universally understandable oversimplifies the nature and purpose of artistic creation.

Art serves multiple functions, and one of its primary roles is to provoke thought, emotion, and dialogue. Art often challenges societal norms, explores complex themes, and provides a platform for self-expression. As such, many works of art are intentionally designed to be thought-provoking, abstract, or unconventional. These qualities can make them less accessible to a mass audience but are essential for pushing the boundaries of artistic expression and engaging with deeper layers of meaning.

Moreover, art often reflects the unique perspective, experiences, and emotions of the artist. It serves as a window into the individual’s creativity, imagination, and inner world. The very essence of art lies in its ability to capture and convey these personal and subjective elements, which may not resonate with everyone but can deeply affect those who do connect with it.

Furthermore, the idea of universal understandability can stifle artistic innovation and diversity. If all art were required to cater to a broad, easily understandable audience, it would discourage experimentation and the exploration of new and unconventional forms of expression. It could lead to a homogenization of art, where creativity is constrained by the need for mass appeal.

It’s important to recognize that different people have different tastes, backgrounds, and levels of exposure to art forms. What is understandable and meaningful to one person may not be to another. The diversity of artistic expression allows for a rich tapestry of voices and perspectives, which contributes to the cultural richness and vitality of society.

That said, there is a place for art that is intentionally created for a broad audience. Many popular films, novels, songs, and other forms of art are designed to entertain, resonate with a wide range of people, and convey messages in a readily understandable way. However, the existence of such art does not negate the value of more abstract, challenging, or niche forms of artistic expression.

In conclusion, the merit of a work of art should not be solely judged by its understandability to most people. Art is a diverse and subjective medium, and its value lies in its ability to provoke thought, emotion, and dialogue, as well as to reflect the unique perspectives and experiences of the artist. Artistic innovation and diversity thrive when artists are free to explore unconventional forms of expression, even if they may not be universally understandable.

Response

I agree with the statement that many important discoveries or creations are accidental, often occurring when seeking the answer to one question leads to the discovery of the answer to another. This phenomenon, known as serendipity, has played a significant role in scientific, technological, and artistic advancements throughout history.

One way in which accidental discoveries occur is through the process of experimentation and observation. Scientists and researchers may set out to investigate a specific question or hypothesis, but during the course of their experiments, they stumble upon unexpected findings. For example, the discovery of penicillin by Alexander Fleming came about when he noticed that a mold, which had accidentally contaminated his bacterial culture, killed the bacteria. This chance observation led to the development of antibiotics, revolutionizing medicine.

Similarly, in the realm of technology, serendipity has often played a role in innovations. For instance, the creation of the microwave oven was a result of accidental discovery. Percy Spencer, an engineer working with radar technology during World War II, noticed that a candy bar in his pocket had melted while he was working with a magnetron. This observation eventually led to the development of microwave cooking.

In the arts, accidental discoveries and creative breakthroughs are also common. Artists and musicians may experiment with different techniques, materials, or melodies, and in the process, they stumble upon novel ideas and styles that they had not originally set out to create. These accidental discoveries often lead to the creation of masterpieces that redefine artistic genres.

However, it’s important to note that serendipity is not entirely random. It often occurs when individuals have a deep understanding of their field and are actively engaged in seeking solutions or answers. In other words, they are “prepared” to recognize the significance of the unexpected findings. Without the foundational knowledge and curiosity that drive the search for answers, accidental discoveries would be less likely.

While serendipity has led to many important discoveries, it is not a reliable or systematic method for advancing knowledge or creating breakthroughs. Research, experimentation, and focused inquiry remain essential components of progress in various fields. Accidental discoveries are more like fortunate accidents that happen along the way.

In conclusion, accidental discoveries have played a significant role in human progress across scientific, technological, and artistic domains. These unexpected findings often occur when individuals are actively engaged in seeking answers and are prepared to recognize the significance of what they encounter. While serendipity is valuable, it should not replace systematic research and inquiry, which remain the primary drivers of innovation and discovery.

Response

I agree with the statement that one of the main benefits of the study of history is to dispel the illusion that people living now are significantly different from people who lived in earlier times. The study of history provides valuable insights into the continuity of human nature, behaviors, and societal patterns over time. While there are certainly differences in technology, culture, and circumstances between eras, the fundamental aspects of human experience remain surprisingly consistent.

History reveals that the core motivations, emotions, and challenges faced by individuals and societies have remained remarkably similar throughout different historical periods. For example, themes of love, ambition, conflict, and resilience are prevalent in literature, art, and historical records from ancient civilizations to modern times. The study of history reminds us that the human condition, including our desires, struggles, and triumphs, has enduring qualities that transcend time and place.

Moreover, examining historical events and societies can help us recognize recurring patterns and lessons. History is replete with examples of the rise and fall of civilizations, the consequences of political decisions, and the impact of social and economic changes. By studying these patterns, we gain valuable insights into the potential outcomes of our actions and decisions today. History serves as a guide for navigating the complexities of the present and making informed choices about the future.

However, it’s important to acknowledge that the study of history can also highlight the significant differences between different eras. Technological advancements, cultural shifts, and societal changes have transformed the way people live and interact with the world. These differences are essential to understanding the context in which historical events occurred and the unique challenges faced by people in the past.

Furthermore, history is not a static or monolithic field but a dynamic and evolving one. New historical discoveries and interpretations continuously reshape our understanding of the past. As such, while there are enduring aspects of human nature, the study of history also emphasizes the importance of context and the need to appreciate the nuances of each historical period.

In conclusion, the study of history provides a valuable perspective that dispels the illusion of significant differences between people living in different times. It reminds us of the timeless aspects of the human experience while also highlighting the importance of understanding historical context and the unique challenges faced by individuals and societies in their respective eras. Through the study of history, we gain a deeper appreciation for both the continuity and evolution of human civilization.

Response

I agree with the statement that learning is primarily a matter of personal discipline and that students cannot be motivated by school or college alone. While educational institutions play a crucial role in providing resources, guidance, and opportunities for learning, the ultimate responsibility for learning and motivation lies with the individual student.

Personal discipline is a fundamental aspect of effective learning. It involves the ability to set goals, manage time, stay organized, and persist in the face of challenges. Students who possess strong self-discipline are better equipped to engage with their studies, complete assignments, and master complex subjects. Without personal discipline, even the best educational programs and teachers may struggle to facilitate effective learning.

Motivation, similarly, is an intrinsic quality that drives individuals to learn and excel. While schools and colleges can create a conducive environment for learning, including engaging lessons and supportive instructors, motivation ultimately comes from within. Students who are genuinely interested in a subject or have a personal connection to their educational goals are more likely to be motivated to learn and succeed.

Furthermore, the idea that external factors alone, such as school or college, can motivate students can be problematic. Relying solely on external motivation can lead to a superficial pursuit of grades or certificates rather than a genuine thirst for knowledge. When students are primarily driven by extrinsic rewards, they may not develop a deep understanding of the material or a lasting passion for learning.

However, it’s important to acknowledge that educational institutions can play a significant role in fostering motivation and discipline. Effective teaching methods, mentorship, and a supportive learning environment can inspire students and provide them with the tools they need to develop discipline and motivation. Great educators have the ability to ignite students’ curiosity and passion for learning, making the educational experience more rewarding and engaging.

Additionally, the relevance and quality of the curriculum can influence students’ motivation. When students see the real-world applications of what they are learning and perceive its value, they are more likely to stay motivated and disciplined in their studies.

In conclusion, while educational institutions have a role to play in facilitating learning and motivation, the primary responsibility for effective learning and personal discipline lies with the students themselves. Learning is a dynamic and individual process that requires self-motivation, personal discipline, and a genuine interest in the subject matter. Educational institutions can provide the tools and support, but the true journey of learning is driven by the student’s intrinsic motivation and commitment.

Response

I agree with the recommendation that scientists and other researchers should focus their research on areas that are likely to benefit the greatest number of people. This approach aligns with the principles of responsible and ethical research, which aim to maximize the positive impact of scientific endeavors on society as a whole.

Focusing research on areas that benefit the greatest number of people is advantageous for several reasons:

1. Social Utility: Science and research are powerful tools for addressing pressing societal challenges and improving the quality of life for a broad population. Research in areas such as healthcare, renewable energy, agriculture, and education has the potential to bring about widespread positive changes.
2. Resource Allocation: Limited research resources, including funding, time, and manpower, must be allocated judiciously. Prioritizing research in areas with broad societal relevance ensures that these resources are put to the best possible use.
3. Ethical Considerations: There is an ethical imperative to prioritize research that has the potential to alleviate suffering, improve health outcomes, enhance living standards, and address global challenges like climate change and infectious diseases.
4. Economic Benefits: Research that benefits a large number of people can have a substantial economic impact by driving innovation, creating jobs, and boosting economic growth.
5. Global Health: Many global health crises, such as pandemics, require a concerted scientific effort. Prioritizing research in these areas is crucial for the well-being of entire populations.

However, it’s important to note that this does not mean all research should be limited to only the most immediately applicable areas. Fundamental research, which may not have immediate practical applications but contributes to our understanding of the world, should still be encouraged. Often, breakthroughs in applied science emerge from seemingly unrelated fundamental research. Moreover, niche research can be valuable in specialized fields where it may not benefit a large number of people directly but could have profound implications for those specific areas.

Additionally, the definition of what benefits the greatest number of people can vary. For example, research into rare diseases may not benefit a large percentage of the population, but it can have an immense impact on the individuals and families affected by these conditions. Therefore, a nuanced approach is needed to balance the broad societal benefit with specialized research.

In conclusion, focusing scientific research on areas likely to benefit the greatest number of people is a responsible and ethical approach. However, it’s essential to strike a balance by also supporting fundamental and specialized research, as these can lead to unexpected breakthroughs and benefits in the long run. Ultimately, responsible research should aim to contribute positively to the well-being of individuals and society as a whole.

Response

I agree with the recommendation that politicians should pursue common ground and reasonable consensus rather than elusive ideals. Pragmatism and compromise are essential components of effective governance, as they enable politicians to address real-world problems and serve the best interests of their constituents.

Here are several reasons why pursuing common ground and reasonable consensus is advantageous:

1. Effective Governance: Politics is the art of the possible. Pursuing common ground and consensus allows politicians to pass legislation and make decisions that can actually have a positive impact on people’s lives. In a diverse society with differing opinions, finding common ground is often the only way to move forward.
2. Stability and Unity: A focus on common ground fosters stability and unity within a nation. Extreme or divisive ideals can polarize society and lead to social unrest. Consensus-building promotes social cohesion and reduces the risk of conflict.
3. Incremental Progress: Politics often involves making incremental progress rather than achieving sweeping change. By finding common ground, politicians can make gradual improvements in areas such as healthcare, education, and the economy, even if they cannot fully realize their ideal visions.
4. Practical Solutions: Real-world problems require practical solutions. Pursuing consensus encourages politicians to seek evidence-based policies and pragmatic approaches that are more likely to succeed.
5. Representation: In a democratic system, politicians represent a diverse range of constituents with varying needs and beliefs. Pursuing common ground allows them to represent the interests of a broader cross-section of society.

However, it’s important to acknowledge that there are situations where pursuing elusive ideals or principles may be justifiable or even necessary. For example:

1. Moral Imperatives: There are moments in history when politicians must stand firmly for moral imperatives, such as human rights or social justice, even if they cannot immediately achieve consensus. Martin Luther King Jr.’s pursuit of civil rights in the United States is a powerful example.
2. Long-Term Vision: Sometimes, visionary leadership is required to set long-term goals and ideals for a society. While immediate consensus may be elusive, articulating a vision can inspire future generations to strive for a better future.
3. Emergencies and Crises: In times of crisis, such as a natural disaster or public health emergency, politicians may need to act decisively rather than seek consensus. However, these actions should be guided by expert advice and the best available evidence.

In conclusion, while politicians should prioritize common ground and reasonable consensus as a general approach to governance, there are exceptions where pursuing ideals or principles is justifiable. The key lies in striking a balance between pragmatic problem-solving and the pursuit of long-term goals or moral imperatives. Effective political leadership requires the ability to adapt to the specific circumstances and needs of a nation while upholding core values and principles.

Scientists and other researchers should focus their research on areas that are likely to benefit the greatest number of people. Write a response in which you discuss the extent to which you agree or disagree with the recommendation and explain your reasoning for the position you take. In developing and supporting your position, describe specific circumstances in which adopting the recommendation would or would not be advantageous and explain how these examples shape your position.

Response

I agree with the recommendation that scientists and researchers should focus their efforts on areas likely to benefit the greatest number of people. This approach not only aligns with ethical principles but also maximizes the societal impact of research endeavors. However, it is essential to acknowledge that there are nuanced situations where the pursuit of niche research can also yield valuable outcomes.

Focusing research on areas with broad societal relevance is advantageous in numerous ways. Firstly, it ensures that limited research resources, including funding and manpower, are channeled into endeavors with the potential for widespread positive impact. Consider the example of medical research. Prioritizing research into common diseases such as cancer, diabetes, and heart disease has led to groundbreaking treatments and improved healthcare for millions of people globally.

Secondly, research that benefits a large number of people has significant economic and social benefits. For instance, advancements in renewable energy technologies have not only addressed environmental concerns but have also created jobs and stimulated economic growth. These benefits extend to both urban and rural communities, illustrating the wide-reaching influence of research with broad applications.

Moreover, the ongoing COVID-19 pandemic has underscored the importance of scientific research that addresses global health challenges. Collaborative research efforts have led to the rapid development of vaccines, which are essential in protecting populations worldwide.

However, it’s important to acknowledge that not all research can be neatly categorized as solely benefiting the greatest number of people. In niche fields, such as archaeology or certain aspects of fundamental physics, research may not have immediate, widespread applications. Yet, this does not diminish its value. For example, research into ancient civilizations may reveal crucial insights into human history and culture, enriching our understanding of the past.

In conclusion, the prioritization of research in areas likely to benefit the greatest number of people is a commendable approach, given its potential for widespread positive impact. However, it’s essential to maintain a balanced perspective that recognizes the value of niche research for its contributions to knowledge and historical understanding. Ultimately, a diversified research landscape allows for both immediate practical benefits and the preservation of human curiosity and cultural heritage.

Response

I wholeheartedly agree with the recommendation that politicians should prioritize pursuing common ground and reasonable consensus over chasing elusive ideals. While ideals can provide inspiration and a vision for the future, the practical realities of governance often necessitate compromise and collaboration for the greater good. There are several compelling reasons for this perspective, and specific examples illustrate the advantages of this approach.

First and foremost, politics is fundamentally about achieving practical outcomes that improve the lives of citizens. In a diverse and pluralistic society, it’s rare to find a single ideal or vision that will satisfy the needs and preferences of all constituents. Consider the case of healthcare policy. While some politicians may have an idealized vision of a perfect healthcare system, the reality is that crafting effective healthcare policies often requires input from a broad spectrum of stakeholders. Pursuing common ground in this context means finding solutions that can garner bipartisan support and deliver tangible benefits to the population, even if they don’t align perfectly with any one ideal.

Furthermore, politics is inherently a process of negotiation and compromise. Elected officials represent constituents with diverse opinions and interests. Attempting to rigidly adhere to elusive ideals can lead to gridlock and political polarization. For instance, the United States has experienced political paralysis in recent years due to extreme ideological positions that make consensus-building challenging. In such situations, focusing on common ground and achievable consensus becomes essential to breaking the deadlock and making progress on important issues.

Moreover, governing effectively often requires pragmatism in the face of complex challenges. Idealized visions may not account for the practical constraints, budgetary limitations, and unintended consequences that policymakers must grapple with. Take environmental policy as an example. While some may hold idealistic views about completely eliminating carbon emissions, the reality is that achieving such a goal may be technologically or economically unfeasible in the short term. Pursuing common ground by implementing incremental steps toward sustainability can be more practical and effective.

However, it’s important to acknowledge that there are instances when adhering to ideals can be justified. For instance, during moments of profound moral urgency, such as the civil rights movement, leaders like Martin Luther King Jr. pursued the ideal of equality with unwavering commitment. Their dedication to this ideal ultimately brought about transformative societal change.

In conclusion, while ideals can serve as aspirational goals, the pragmatic nature of politics often necessitates a focus on common ground and consensus. Real-world governance requires compromise, negotiation, and the ability to find practical solutions to complex challenges. By prioritizing common ground, politicians can better serve the diverse needs of their constituents and navigate the complexities of the political landscape effectively.