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Large brain size does not always mean that an animal is highly intelligent. Brain size is necessarily associated with overall body size, with large animals having large brains and small animals having small brains. However, it is still necessary for there to be some minimum amount of circuitry (brain cells and processes) present for a species to have the potential to be highly intelligent, whatever way the term intelligence is defined. A measure of relative brain size that has been applied to a variety of species is the encephalization quotient (EQ), the ratio of brain mass to body size. The EQ is calculated by measuring the relative size of different body parts over a wide range of species. An EQ of 1.0 means that the brain is exactly the size one would expect for an animal of a particular size, an EQ higher than 1.0 means that a species is relatively brainy. Bottlenose dolphins have a very high EQ, about 2.8 or higher. Thus, dolphin brains are not simply absolutely large: they are relatively very large as well. Humans, by the way, have extremely high EQ values, estimated to be in the neighborhood 7.5, making our species the brainiest in existence. Nonetheless, it is worth noting that EQ levels in several species of odontocetes (toothed whales, dolphins, and porpoises) are significantly higher than is the case for any primate except our own species. The EQ value for a species relates to a number of general measures of cognitive processing ability in different mammals, as well as to a number of life history patterns in mammals. EQ may be correlated with life span, home-range size, and social systems that characterize a particular species. Oddly enough, the relationships found between EQ and other factors in primates and some other mammals do not appear to apply as well to cetaceans (whales, dolphins, and porpoises), including the bottlenose dolphin. The reasons for the larger-than-normal brain of the bottlenose dolphin (and indeed of small odontocetes in general) are not clearly understood. To navigate and detect prey, dolphins emit calls into the environment and then listen to the echoes of the calls that return from nearby objects, a process known as echolocation. Among the more plausible suggestions for large brain size are that the complexity of processing high-frequency echolocation information requires the development of large centers in the cerebral hemispheres, and/or that the degree of sociality exhibited by many species, in which individual animals recognize and have particular long- and short-term relationships with a number of other individuals, has favored the evolutionary development of a large, complex brain. Some authors develop a strong case that extreme development of the auditory (hearing) system may be the primary reason for the dolphin’s large brain. This opinion is supported by observations that the auditory regions of the dolphin brain are 7 to 250 times larger than the equivalent regions of the human brain and by observations of very fasts auditory brain stem responses to sounds. It should be noted, however, that sperm whales are very social and good echolocators (that is, good at locating objects by emitting sounds and detecting the reflections given back), yet their EQ values are low—only about 0.3. Even some small, less social odontocetes such as Indus river dolphins echolocate well but do not possess the exceptionally large brains that bottlenose dolphins do. Noted biologist Peter Tyack has studies dolphin brains and argues persuasively that large brains evolved in dolphins to permit complex social functions. As is the case with certain primates, bottlenose dolphins and certain other large-brained odontocetes have developed societies in which there exists a balance between cooperation and competition among particular individuals. The social politics of chimpanzees and dolphins show some remarkable similarities, especially in terms of the importance of social relations extending far beyond the mother-offspring relationship to include individuals of both sexes across the age range. The development of such complex societies may have favored the evolution of large brain size. The reason that dolphins have a large brain continues to be somewhat elusive but there must be a reason, since maintenance of brain tissue is metabolically expensive. The adult human brain, for example, may only represent 2 percent of the body weight, but it can account for nearly 20 percent of the metabolic rate (the energy used). 【Paragraph 1】 Large brain size does not always mean that an animal is highly intelligent. Brain size is necessarily associated with overall body size, with large animals having large brains and small animals having small brains. However, it is still necessary for there to be some minimum amount of circuitry (brain cells and processes) present for a species to have the potential to be highly intelligent, whatever way the term intelligence is defined. A measure of relative brain size that has been applied to a variety of species is the encephalization quotient (EQ), the ratio of brain mass to body size. The EQ is calculated by measuring the relative size of different body parts over a wide range of species. An EQ of 1.0 means that the brain is exactly the size one would expect for an animal of a particular size, an EQ higher than 1.0 means that a species is relatively brainy. 1. According to paragraph 1, what does it mean for an animal to have an EQ higher than 1.0? A. Its brain has more mass than similarly sized brains of other animals. B. Its brain is larger than expected for the animal’s overall body size. C. Its brain is larger than that of most other animals. D. Its brain is larger than that of any animal with an EQ of less than 1.0. 【Paragraph 2】 Bottlenose dolphins have a very high EQ, about 2.8 or higher. Thus, dolphin brains are not simply absolutely large: they are relatively very large as well. Humans, by the way, have extremely high EQ values, estimated to be in the neighborhood 7.5, making our species the brainiest in existence. Nonetheless, it is worth noting that EQ levels in several species of odontocetes (toothed whales, dolphins, and porpoises) are significantly higher than is the case for any primate except our own species. The EQ value for a species relates to a number of general measures of cognitive processing ability in different mammals, as well as to a number of life history patterns in mammals. EQ may be correlated with life span, home?range size, and social systems that characterize a particular species. Oddly enough, the relationships found between EQ and other factors in primates and some other mammals do not appear to apply as well to cetaceans (whales, dolphins, and porpoises), including the bottlenose dolphin. 2. Paragraph 2 supports which of the following statements about the EQ levels of various animals? A. Bottlenose dolphins have higher EQ levels than other odoncetes do B. The EQ levels of bottlenose dolphins are more closely associated with their life history patterns than the EQ levels of primates are. C. Bottlenose dolphins belong to a group of animals whose EQ levels are higher than those of any primate except humans. D. The brains of bottlenose dolphins are larger for these dolphins’ size than brains of humans are for humans’ size. 3. Which of the following is NOT identified in paragraph 2 as a factor that may be correlated with EQ? A. The species’ social organization B. The species’ ecological role in the environment C. The extent of the range that species members need for daily activities D. The number of years that species members live on average 4. Paragraph 2 answers which of the following questions about EQ? A. Which life history patterns correlate best with EQ values in whales, dolphins, and porpoises? B. Is the EQ of bottlenose dolphins significantly higher than that of other dolphins? C. What are the differences in EQ levels among different species of odontocetes? D. Do the same factors that correlate with EQ in primates correlate well with EQ in bottlenose dolphins? 【Paragraph 3】 The reasons for the larger-than-normal brain of the bottlenose dolphin (and indeed of small odontocetes in general) are not clearly understood. To navigate and detect prey, dolphins emit calls into the environment and then listen to the echoes of the calls that return from nearby objects, a process known as echolocation. Among the more plausible suggestions for large brain size are that the complexity of processing high-frequency echolocation information requires the development of large centers in the cerebral hemispheres, and/or that the degree of sociality exhibited by many species, in which individual animals recognize and have particular long- and short-term relationships with a number of other individuals, has favored the evolutionary development of a large, complex brain. Some authors develop a strong case that extreme development of the auditory (hearing) system may be the primary reason for the dolphin’s large brain. This opinion is supported by observations that the auditory regions of the dolphin brain are 7 to 250 times larger than the equivalent regions of the human brain and by observations of very fasts auditory brain stem responses to sounds. It should be noted, however, that sperm whales are very social and good echolocators (that is, good at locating objects by emitting sounds and detecting the reflections given back), yet their EQ values are low—only about 0.3. Even some small, less social odontocetes such as Indus river dolphins echolocate well but do not possess the exceptionally large brains that bottlenose dolphins do. 5. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. It is plausible that the development of high-frequency echolocation, large centers in the cerebral hemispheres, and/or a high degree of sociality may have contributed to the development of large brains. B. For an animal to recognize and have long- and short-term relationships with a number of other individuals, the animals must develop large centers in the cerebral hemispheres. C. Processing high-frequency echolocation information may have required a large, complex brain that already had the capacity to develop and recognize long- and short-term social relationships with multiple other individuals. D. The demands of processing high frequency echolocation information and/or a high degree of sociality may have favored the evolutionary development of a large, complex brain. 6. Why does the author include the information that “some small, less social odontocetes such as Indus river dolphins echolocate well but do not possess the exceptionally large brains that bottlenose dolphins do”? A. To argue that in odontocetes, sociality determines whether an animal has a large brain B. To argue that echolocation does not necessarily involve exceptionally fast auditory brain stem responses to sounds C. To help explain why effective echolocation does not necessarily require extreme development of the auditory system D. To provide evidence that weakens the theory that the large brains of bottlenose dolphins are explained by their need to echolocate. 【Paragraph 4】 Noted biologist Peter Tyack has studies dolphin brains and argues persuasively that large brains evolved in dolphins to permit complex social functions. As is the case with certain primates, bottlenose dolphins and certain other large?brained odontocetes have developed societies in which there exists a balance between cooperation and competition among particular individuals. The social politics of chimpanzees and dolphins show some remarkable similarities, especially in terms of the importance of social relations extending far beyond the mother-offspring relationship to include individuals of both sexes across the age range. The development of such complex societies may have favored the evolution of large brain size. 7. According to paragraph 4, what is true about bottlenose dolphin societies? A. There is far more cooperation than competition among individuals. B. Long-term social relationships tend to exist primarily between individuals of the same sex and similar ages. C. They are similar to chimpanzee societies in terms of the types of social relationships that exist. D. They are far more complex than the societies of any other species of odontocetes. 【Paragraph 5】 The reason that dolphins have a large brain continues to be somewhat elusive but there must be a reason, since maintenance of brain tissue is metabolically expensive. The adult human brain, for example, may only represent 2 percent of the body weight, but it can account for nearly 20 percent of the metabolic rate (the energy used) 8. The word “elusive” in the passage is closest in meaning to A. hard to prove B. hard to identify C. misunderstood D. controversial 【Paragraph 1】 Large brain size does not always mean that an animal is highly intelligent. Brain size is necessarily associated with overall body size, with large animals having large brains and small animals having small brains. ■However, it is still necessary for there to be some minimum amount of circuitry (brain cells and processes) present for a species to have the potential to be highly intelligent, whatever way the term intelligence is defined. ■A measure of relative brain size that has been applied to a variety of species is the encephalization quotient (EQ), the ratio of brain mass to body size. ■The EQ is calculated by measuring the relative size of different body parts over a wide range of species. ■An EQ of 1.0 means that the brain is exactly the size one would expect for an animal of a particular size, an EQ higher than 1.0 means that a species is relatively brainy. 9. Look at the four squares【■】that indicate where the following sentence could be added to the passage. This requirement suggests that having a brain that is large relative to an animal’s size might be a clue to greater intelligence. Where would the sentence best fit? 10.【Directions】An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because the express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Large brain size does not necessarily mean that an animal is especially intelligent. ● ● ● Answer Choices A. Bottlenose dolphins have a high EQ, a measure of the ratio of brain mass to body mass that correlates with various cognitive abilities and possibly with life-history patterns in animals. B. The need to process high-frequency sounds for echolocation has been offered as an explanation for bottlenose dolphins’ unusually large brains, but not all good echolocators have high EQs. C. The brain size of bottlenose dolphins is strongly correlated with the amount of cooperation and competition in relationships outside the mother-offspring relationship. D. Scientists are now using findings from their studies of bottlenose dolphins to determine the connection between the presence of a large brain and the potential for intelligence in other species. E. Bottlenose dolphins, like certain other large-brained animals, have complex social relationships, so their large, metabolically expensive brains may have evolved partly to permit complex social functioning. F. Biologists disagree about whether the larger-than-usual brain of the bottlenose dolphin makes it more intelligent or more metabolically efficient than other mammals with less brain mass. |
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