1 Many species of animals live in a group with some kind of social organization. This organization is based on aggressiveness, intolerance, and the dominance of one individual over another. Two opposing forces are at work. One is mutual attraction of individuals; the other is a negative reaction against crowding, the need for personal space.
2 Each individual occupies a position in the group based on dominance and submissiveness. In its simplest form, the groups include an alpha individual dominant over all others, a beta individual dominant over others except the alpha, and finally an omega individual subordinate to all others. Individuals settle social rank by fighting, bluffing, and threatening at initial encounters between any given pair of individuals or a series of such encounters. Once individuals establish social rank, they maintain it by habitual subordination of those in lower positions. They reinforce this relationship by threats and occasional punishment meted out by those of higher rank. Such organization stabilizes and formalizes competitive relationships and resolves disputes with a minimum of fighting and wasted energy.
3 Social dominance plays a role in population regulation when it affects reproduction and survival in a density-dependent manner. An example is the wolf. Wolves live in small groups of 6 to 12 or more individuals called packs. The pack is an extended kin group consisting of a mated pair, one or more juveniles from the previous year who do not become sexually mature until the second year, and several related, non-breeding adults.
4 The pack has two social hierarchies, one headed by an alpha female and the other headed by an alpha male, the leader of the pack, to whom all other members defer. Below the alpha male is the beta male, closely related, often a full brother, who has to defend his position against pressure from males below.
5 Mating within the pack is rigidly controlled. The alpha male (occasionally the beta male) mates with the alpha female. She prevents lower-ranking females from mating with the alpha and other males, while the alpha male inhibits other males from mating with her. Therefore, each pack has one reproducing pair and one litter of pups each year. They are reared cooperatively by all members of the pack.
6 The size of the packs, which is heavily influenced by the availability of food, governs the level of the wolf population in a region. Priority for food goes to the producing pair. At high pack density, individuals may be expelled or leave the pack. Unless they have the opportunity to settle successfully in a new area and form a pack, they may not survive. Thus, at high wolf densities mortality increases and birthrates decline. When the population of wolves is low, sexually mature males and females leave the pack, settle in unoccupied habitat, and establish their own packs with one reproducing female in each. In this case, nearly every sexually mature female reproduces, and the wolf population increases. At very low densities, however, females may have difficulty in locating males with whom to establish a pack and so fail to reproduce or even survive. (Smith, Robert Leo and Thomas M. Smith. Elements of Ecology, 4th ed. 2000, p. 171)
Which of the following expresses the main point of this passage?
In this selection, the author's main purpose is to
Which of the following best defines the word dominant as it is used in paragraph 2 of the selection?
According to information in the passage, what happens to the wolf population in a region at high pack density?
The main idea of paragraph 2 is that
Long thought to be a case of mistaken identity, the discovery of the Bornean rainbow toad by European explorers in 1924 was recently verified by scientists. The explorers had made a black-and-white sketch of an unusual toad they had found in the jungles of Southeast Asia, christening it the Bornean rainbow toad. Skeptical but curious, scientists recently went to look for the toad— and ended up finding three specimens.
The passage implies which of the following about the Bornean rainbow toad?
Television has been the primary source of information and entertainment for most Americans over the last 50 years. However, with Internet use on the rise year after year, some may wonder if surfing the net will soon surpass watching television as Americans' primary leisure activity. Indeed, some recent surveys show that time spent on the Internet is now greater than time spent in front of the television. However, this statistic may not tell the whole story, as 59% of Americans say they multitask, using the Internet and watching TV simultaneously.
The main idea of the passage is that television:
Plywood, while not the most pleasing wood to look at, has become an incredibly important building material in house construction. It is flexible, inexpensive, and strong. Its strength is due to layers of thin wood glued on top of each other with the grain of each layer making a right angle with the grain of the layer below it. This way of layering the sheets of wood makes plywood difficult to break. According to the passage, the arrangement of the layers of thin wood explains plywood's:
The 1922 German Expressionist film Nosferatu, directed by F. W. Murnau, is considered one of the most influential films in cinematic history—while also being a classic vampire movie. The film is closely based on Bram Stoker's 1897 novel, Dracula; however, the villain in the film is called "Count Orlok" rather than "Count Dracula." The reason is that the small studio that produced the film, Prana Film, was unable to secure the rights to Stoker's novel. In fact, shortly after finishing Nosferatu, its one and only film, Prana went bankrupt in order to dodge copyright lawsuits from Stoker's widow. Why does the author say that the vampire in Nosferatu is named "Count Orlok" and not "Count Dracula"?
Guillermo Gonzalez Camarena became a successful inventor at an early age. By the age of seven, he had constructed a variety of electronically-propelled toys to play with; he later designed and built his own amateur radio and a functioning telescope. In 1940, when he was only 23, Camarena obtained the world's first patent for color television. Camarena's early color television transmission system was the first one to be approved by the U.S. Federal Communications Commission. Other color-television technologies came after Camarena's patented invention, but his system is still used by a number of scientists today. In sentence 2, the word "functioning" most nearly means:
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