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The author mentions "studies of lake and shallow ocean sediments" primarily in order to
The passage suggests which of the following about the reservoirs at Tikal?
The passage suggests which of the following about cenotes?
A team of researchers has claimed that by drilling below the Earth`s surface, they have been able to recover microorganisms that inhabit depths where it was previously thought that no life existed. Although other microorganisms that were at first thought to have been recovered from these depths were later determined merely to have come from surface soil, that cannot be so in this case, because________.
Which of the following most logically completes the argument?
Competition from horse appears to have been a factor in historical wildlife distribution and abundance. In archaeological studies in the Columbia River basin in North America, horse bones have been found alongside bison bones, indicating that bison were still present in the Columbia Basin at the time horses appeared, that is, sometime after about 1720. Researchers hypothesize that the introduction of the horse eventually led to the extinction of bison in the Columbia Basin in two ways. First, the horse acted as a direct foraging competitor to the bison. Horse and bison diets have considerable overlap, and competition for forage may have been high as horse numbers increased over time. Second, the introduction of horses improved the hunting efficiency of the Native Americans.
In the context of the passage as a whole, the highlighted sentence serves to
According to the passage, which of the following statements about bison in the Columbian Basin is true?
While the history of the Earth`s moon is well understood, the origin of the Martian moons, Phobos and Deimos, is still a mystery in spite of numerous space missions sent to Mars. One theory, based on striking similarities between the physical characteristics of the surfaces of Mars` moons and the surfaces of numerous objects in the asteroid belt, is that the Martian moons were formed far away from Mars and then captured by the planet`s gravitational attraction. However, this theory cannot account for the current near-equatorial and near-circular orbits of the moons. The fact that these orbits are consistent with expected orbits of objects accreted around Mars motivated some astrophysicists to propose instead that Phobos and Deimos were formed from a disk of debris in Mars` orbit.
The passage suggests that if the Martian moons were formed far away from Mars, it is likely that
According to the passage, "one theory" is motivated by
Spiders of the species Argiope build distinctive zig-zag patterns, called stabilimenta, into their webs. Recent research has established that Argiope spiders use stabilimenta to collect drinking water. This discovery, far from discrediting the long-standing hypothesis that stabilimenta serve to reinforce the webs, actually supports that hypothesis since________.
Which of the following, if true, most logically completes the argument?
While studying different-sized ant colonies, Cole discovered that when there were only a few ants in the space provided, each individual exhibited a chaotic pattern of activity and rest. As the density of the colony increased by the addition of more ants, Cole observed a sudden transition to dynamic order: patterns of activity and rest over the colony as a whole suddenly changed from chaotic to rhythmic. Why should the density of ants play an apparently crucial role in the transition from chaotic to ordered behavior? Ants interact with one another, and an active ant encountering an inactive one will stimulate the latter into movement. At low densities there are few encounters, but at higher densities activity can spread like a contagion through the colony.
According to the passage, which of the following statements about ant interactions is true?
In the context in which it appears, "ordered" most nearly means
Before 1865, magazines created specifically for women in the United States targeted an elite class of readers. Relatively expensive, they carried little or no advertising and generally contained literary, etiquette, and fashion material. After 1865, readership increased significantly: literacy increased; innovations in printing allowed publication of hundreds of copies in a short time; an expanded railroad, improved roads, and a larger and cheaper postal service permitted more efficient and reliable distribution; and aggressive solicitation of advertisers allowed publishers to reduce prices of the magazines, which now focused on middle-class women. While the entertainment function of the earlier magazines persisted, as did advice columns and articles on cultural affairs and other nonfiction topics, women as consumers received increasing attention, particularly through the newly important ads.
According to the passage, which of the following was a feature common to women`s magazines published both before and after 1865?
It can be inferred that before 1865, the readership that women`s magazines could reach was restricted by which of the following factors?
Basic population biology demonstrates that widespread use of common nonspecific insecticides must inevitably exacerbate the very problems these insecticides were designed to solve because, in addition to killing "bad" insects (those that eat crops), these insecticides have a "side effect", they also kill "good" insects (those that prey on the bad insects) and indirectly reduce the good insects` birth rate. While insecticide use will decimate both populations equally, the bad insects will rebound much more quickly. In predator/prey systems, predators control the death rate of their prey by eating them, while the prey control the birth rate of their predators by providing nourishment. When population numbers of both decline, therefore, the prey`s death rate is dramatically reduced because there are many fewer predators, while the predators` birth rate is dramatically reduced because there is less food and it is harder to find. The birth rate of the prey is much less affected, and thus those insects feeding on crops are capable of rebounding first, then, in the resulting environment that is largely devoid of predators, they reach higher numbers than before.

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