Questions 1-10 By far the most important United States export product in the eighteenth and nineteenth centuries was cotton, favored by the European textile industry over flax or wool because it was easy to process and soft to tile touch. M...
Questions 31-39 Perhaps one of the most dramatic and important changes that took place in the Mesozoic era occurred late in that era, among the small organisms that populate the uppermost, sunlit portion of the oceans--the plankton. The ter...
If food is allowed to stand for some time, it putrefies .When the putrefied material is examined microscopically ,it is found to be teeming with bacteria. Where do these bacteria come from , since they are not seen in fresh food? Even until...
Questions 11-19 The origins of nest-building remain obscure, but current observation of nest-building activities provide evidence of their evolution. Clues to this evolutionary process can be found in the activities of play and in the behav...
Because the low latitudes of the Earth, the areas near the equator, receive more heat Than the latitudes near the poles, and because the nature of heat is to expand and move, Heat is transported from the tropics to the middle and high latit...
Newspaper publishers in the United States have long been enthusiastic users and distributors of weather maps. Although some newspapers that had carried the United States Weather Bureaus national weather map in 1912 dropped it once the novel...
In eighteenth-century colonial America, flowers and fruit were typically the province of the botanical artist interested in scientific illustration rather than being the subjects of fine art. Early in the nineteenth century, however, the Pe...
Scientists have discovered that for the last 160,000 years, at least, there has been a consistent relationship between the amount of carbon dioxide in the air and the average temperature of the planet. The importance of carbon dioxide in re...
It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species death vary from si...
The Moon, which has undergone a distinct and complex geological history, presents a striking appearance. The moon may be divided into two major terrains: the maria (dark lowlands) and the terrace( bright highlands). The contrast in the refl...
Some animal behaviorists argue that certain animals can remember past events, anticipate future ones, make plans and choices, and coordinate activities within a group. These scientists, however, are cautious about the extent to which animal...
The first birds appeared during late Jurassic times. These birds are known from four very good skeletons, two incomplete skeletons, and an isolated feather, all from the Solnhofen limestone of Bavaria, Germany. This fine-grained rock, which...
Question 10-19 Geographers say that what defines a place are four properties: soil, climate, altitude, and aspect, or attitude to the Sun. Floridas ancient scrub demonstrates this principle. Its soil is pure silica, so barren it supports on...
Newspaper publishers in the United States have long been enthusiastic users and distributors of weather maps. Although some newspapers that had carried the United States Weather Bureaus national weather map in 1912 dropped it once the novel...
Question 10-19 Geographers say that what defines a place are four properties: soil, climate, altitude, and aspect, or attitude to the Sun. Floridas ancient scrub demonstrates this principle. Its soil is pure silica, so barren it supports on...
Question 30-40 Because the low latitudes of the Earth, the areas near the equator, receive more heat Than the latitudes near the poles, and because the nature of heat is to expand and move, Heat is transported from the tropics to the middle...
Question 20-30 It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction? When a species is no longer adapted to a changed environment, it may perish. The exact causes of a species dea...
Questions 21-29 Under the Earths topsoil, at various levels, sometimes under a layer of rock, there are deposits of clay. Look at cuts where highways have been built to see exposed clay beds; or look at a construction site, where pockets of...
Question 41-50 The Moon, which has undergone a distinct and complex geological history, presents a striking appearance. The moon may be divided into two major terrains: the maria (dark lowlands) and the terrace( bright highlands). The contr...
Questions 41-50 The Homestead Act of 1862 gave beads of families or individuals aged twenty-one or older the right to own 160 acres of public land in the western United States after five years of residence and improvement. This law was inte...
