The following two passages are both tough biology texts. Use them for additional practice with difficult Natural Science passages in the Reading section.
PASSAGE 1 45 NATURAL SCIENCE: 5 10 15 20 25 30 35 40 e genetic history of a species is most commonly traced through its DNA and physical characteristics. e more similar two species are, the more closely related they are. One reason this research is useful is that it provides information about approximately when a physical trait developed. For example, venomous snakes, lizards, and iguanas all share the same nine toxins, so the evolution of venom must have occurred before the three groups separated into distinct families. It was only after the venom was part of their genetic makeup that modern species began emerging. e order Squamata, in particular, has been the subject of much scienti c debate. Squamates are scaled reptiles including all snakes and lizards. It once was believed that iguanas were the oldest group of squamate. DNA evidence, however, has demonstrated that geckos are likely more ancient. Similarly, scientists once believed that many limbless creatures were closely related. However, continued examination of DNA evidence has revealed that these creatures evolved independently of each other. ere are several reasons for the confusion involving Squamata evolution. One is that fossils of these animals have been found in poor condition and limited quantities. Another is that the process by which squamates change into new species is di erent than it is for other animals. Squamates are unlikely to evolve into new species except in particularly harsh conditions. erefore, one geographic area could have a huge number of bird species, but only a few species of snakes and lizards. Tracing an evolutionary lineage with this pattern is very challenging. e uniqueness of the order Squamata forces scientists to nd new ways to measure relationships between di erent species within the order. DNA analysis has proved exceptionally useful, but observing physical and behavioral characteristics are can provide insight as well. It is only with the collaboration of DNA and behavioral studies that comprehensive analysis of Squamata evolution is e ectively performed. One challenge of categorizing and evaluating behavior is the high degree of individuality. Some behaviors are learned, while others are inherited. However, when a certain behavior is exhibited by almost all members of a species or subspecies, it is reasonable to conclude that the behavior is inherited. Just as similar DNA sequences or similar physical characteristics indicate closely related 50 55 60 65 70 75 80 85 90 species, similar sets of behavioral patterns indicate biological relationships, as well. For example, the family Viperidae, generally known as Vipers, is composed of several di erent types of venomous snakes. At one point, all vipers had nearly the same genetic and behavioral characteristics. As they evolved, however, di erences emerged, and subfamilies were created, including both Crotalinae (pit vipers) and Viperinae (pitless vipers). In terms of genetic di erences, pit vipers have a heat-sensing pit organ located between their eyes and nose. Pitless vipers lack that organ. Both subfamilies continued to evolve, until there are now 151 species of pit vipers and 66 species of pitless vipers known. Behavioral di erences are apparent, too. In a recent study of 14 species of vipers, including 10 pit vipers and 4 pitless vipers, all vipers engaged in combat similarly. In every instance, the viper would lift his head and body o the ground in a threatening stance. He would also attempt to force his opponent to the ground by pushing with his entire body weight. Because this behavior is ubiquitous to all vipers, it is likely that the behavior evolved before the Viperidae family separated into subfamilies. Other behavior likely emerged only after Viperidae had split into di erent geneses and species. Nearly all Crotalinae used a chin rub as part of their mating rituals. Chin rubs were much rarer in the subfamily Viperinae. It is probable that family Viperidae did not utilize the chin rub before it divided into subfamilies. After the division, Crotalinae developed the chin rub technique. As Crotalinae developed into each of its 151 species, the chin rub behavior was passed down. us, the chin rub appears only in rarely outside the Crotalinae subfamily. Some behaviors likely appeared much more recently. e black-headed bushmaster and the central American bushmaster are both species of pit vipers. Both exhibit cloacal gaping prior to mating. Yet few other pit viper species show this behavior. It is likely, therefore, that this behavior was not learned until after the family had already signi cantly divided and several species were already in existence. Combining the fossil records, DNA analysis, and these newly observed relationships yields some interesting conclusions about the evolution of snakes. Continued research should focus on precise and continual observations of behavior in a snake s lifestyle. e ongoing challenge lies in observing behavior that is truly natural. Snakes in captivity often behave
95 di erently than snakes in the wild. A researcher also may not be aware when a courtship or combat communication has begun. is results in recording only the middle and end of an interaction. e rst few steps can be completely lost. Observers can also fail to note behaviors that seem obvious. Without a complete and comprehensive system of observation, the data will be incomplete. However, the current research illustrates the potential for a deeper understanding of the evolutionary history of snakes through continued observation. 1. e passage states that: A. the evolution of snakes depends on their living conditions. B. observations of snake behavior are never completely accurate. C. the majority of snake species exhibit similar combat behaviors. D. DNA evidence has created confusion in determining the evolution of snakes. 4. e passage indicates that a mistaken belief scientists have held is: F. behavioral characteristics cannot be passed down genetically. G. the order Squamata has several unique characteristics. e passage suggests that each of the following was used to determine the relationship between species EXCEPT: A. B. C. D. 6. DNA. observational studies. species diversity. fossil records. e author is most likely to believe the next logical study on the evolution of Squamates should focus on: F. complete observation of squamates in their natural habitat. G. DNA comparisons of di erent species of Squamates. H. male-male combat maneuvers. J. mating rituals. e author would be most likely to agree with which of the following? F. Two snake species that exhibited the similar behavior have evolved from one another. G. Behavioral traits should be included in determining species relationships. H. All pit vipers exhibit cloacal gaping. J. Snakes and lizards are more distantly related than once thought. 3. 5. e main purpose of this passage is to: A. explain the di erences between species in the order Squamata. B. describe di erent behaviors that squamates exhibited. C. examine competing theories about squamate evolution. D. describe a way to relate behavior to evolutionary theory. 2. H. iguanas are the oldest remaining species of the order Squamata. J. observational studies are of no use to scientists. 7. to: e purpose of the second paragraph (lines 11 19) is A. explain the importance of terrain to snakes and lizards. B. discuss a unique feature of snakes and lizards. C. emphasize the importance of observational studies. D. establish the need for further studies of Squamata species. 8. According to the rst paragraph: F. DNA is the most common way to trace the genetic history of a species. G. similar physical traits indicate a close relationship between species. H. venom is used only in snakes, lizards, and iguanas. J. snakes, lizards, and iguanas share a common ancestor.
9. What does the passage state is a di culty of behavioral observation? A. Squamates are often di cult to nd in their natural habitats. B. Observational records of snakes in captivity can be incomplete. ere are too many subtle di erences in behavc. ior to be recorded. D. It is unclear what behaviors are relevant to a study. 10. e word ubiquitous (line 64) as used in the passage most nearly means: F. G. H. J. violent. unknown. rare. common.
Passage 1 Write in whether you got each problem right or wrong (or left it blank). If your answer was correct, put a 1 in every blank to the right of that problem. Sum up each column and compare your total to the total possible Out Of points in each column. Right/ Wrong/Blank Main Ideas/ Author s Approach Problem Correct Answer 1 D 2 G 3 A 4 H 5 C 6 F 7 D 8 J 9 B 10 J Details Relationships Meanings Generalizations of Words Total Out Of 10 3 3 1 1 2
Passage 1 Solution 1. D. e main purpose of this passage is to describe a way to relate behavior to evolutionary theory. Main Idea e passage focuses on associating squamate behavior with its evolutionary history. DNA and fossil evidence have been used in to trace relationships among animals, but the author believes these should be supplemented by behavioral studies as well. e author points out its relevance throughout the passage. Tracing an evolutionary lineage is very challenging (lines 28 29). Observing physical and behavioral characteristics can provide insight (lines 33 34). Similar sets of behavioral patterns indicate biological relationships (lines 45 46). Combining the fossil records, DNA analysis, and these newly observed relationships yields some interesting conclusions about the evolution of snakes (lines 84 86). Answer choice (D) is correct. Answer choices (A) and (B) can be eliminated as too narrow. Di erent behaviors and di erences between species are discussed, but are not the focus of the passage. Answer choice (C) isn t discussed in the passage. Competing theories about squamate evolution are never described. e author would be most likely to agree with which of the following? Behavioral traits should be included in 2. G. determining species relationships. Generalizations e author talks about di erent behaviors and how they re ect relationships between species throughout the passage. He says that similar sets of behavioral patterns indicate biological relationships (lines 45 46). Answer choice (G) is correct. 3. A. e passage states that the evolution of snakes depends on their living conditions. Details e author talks about the speci c evolution of snakes in paragraph three. He says Squamates are unlikely to evolve into new species except in particularly harsh conditions (lines 24 26). Because snakes are one type of squamate, the conditions in which they live a ect their evolution. Answer choice (A) is correct. Answer choice (B) is too extreme. Observations of snakes may be di cult, but the author doesn t claim they are never completely accurate. Answer choices (C) an (D) are contradicted by the passage. e passage indicates that a mistaken belief scientists have held is iguanas are the oldest remaining species of the 4. H. order Squamata. Details DNA evidence has led to scientists reconsidering several things according to the passage. e author tells us that it was once believed that iguanas were the oldest group of squate. DNA evidence, however, has demonstrated geckos are likely more ancient (lines 13 16). Iguanas are certainly not the oldest remaining species of Squamates. Answer choice (H) is correct.
PASSAGE 2 45 NATURAL SCIENCE: adapted from The Role of Iron in Prion Disease and Other Neurodegenerative Diseases by N. Singh. 5 10 15 20 25 30 35 40 A growing number of conditions are associated with accumulation of iron in the brain. Some well-known a ictions, such as Alzheimer s and Parkinson s disease, represent challenges to researchers. e underlying cause of each is complex and only partially known. One focus of current research is obtaining a better understanding of the role iron plays in these disease pathways. In patients a icted with either disease, iron levels within the brain are consistently abnormal. e result of this research is likely to help in the development of targeted treatment strategies. Iron is essential for vital metabolic processes. However, unshielded iron is toxic. Iron metabolism is therefore tightly regulated by proteins to maintain cellular homeostasis. When cellular homeostasis is achieved, iron levels are stable. Each cell processes the amount of iron needed, no more, no less. Lack of stability is known as dyshomeostasis. Dyshomeostasis can have dangerous and even lethal e ects. Distinguishing dyshomeostasis is a cause or an e ect of brain disorders is the source of much debate. e resulting situation involves a complex of known and unknown factors. Toxic levels of iron are present in several brain disorders. For many diseases, the process of iron dyshomeostasis is clear. A particular protein or protein pathway is disrupted and iron levels rise or fall. It is known when this occurs, and can often be treated if necessary. Yet many proteins, particular within the brain, have poorly de ned function. Some proteins participate in iron regulation to some extent, but do not work independently. If these are the proteins involved in a brain dysfunction, the exact cause of the disease can be hard to determine. Even learning which proteins are involved is a challenge. ese complex proteins are involved in several diseases, including Alzheimer s and Parkinson s. Fixing the dyshomeostasis is more di cult, and even after it is xed, it is unclear what e ect there will be on the patient. Traditional studies of these disorders suggest that iron accumulation does not cause neural toxicity but instead occurs after cell death. is would imply that treatment of iron levels should not be a priority. Emerging data, however, requires a reconsideration of this concept. ree major observations lend themselves to the idea that iron dyshomeostasis is a critical component of disease progression. First, the onset of these diseases is accompanied by an increase in iron-regulating 50 55 60 65 70 75 80 85 90 proteins. Because this change occurs so early in the disease progression, iron levels are clearly impacted throughout the disorder. Second, these proteins interact in a way that attracts and retains iron. is increases the total amount of iron, while decreasing the usable iron available; neurotoxicity results. Lastly, neurons that are not directly a ected respond with a coping mechanism worsening the iron dyshomeostasis. Regional accumulation of iron in the brain has been reported in both Alzheimer s and Parkinson s disease su erers. ough each disorders increase iron, the method of accumulation is di erent. In Alzheimer s, iron accumulates in amyloid plaques. e plaques have a high a nity for iron, and as more iron accumulates, the a nity increases. us, increasingly dangerous amounts of iron are collected and retained in the plaques. Because more iron levels creates more attraction to iron, which increases iron even further, this cycle is di cult to disrupt. Simultaneously, iron-regulatory proteins are malformed. ey have limited ability to regulate the amount of iron in the brain. e development of brain iron dyshomeostasis in Alzheimer s is therefore multifaceted and a full understanding of the underlying mechanism is lacking. Parkinson s disease results from multiple factors and its cause is unknown. However, it is always associated with loss of dopamine-producing neurons. Studies have invariably shown that there are also signi cantly elevated levels of iron in the brain. What causes the elevation and where the iron accumulates is unclear. It has been attributed to secondary causes, not linked directly to the cause of the disease. Nonetheless, treatment of iron accumulation results in a reduction of Parkinson s symptoms. is suggests that accumulation of iron in Parkinson s is an active process, not a mere symptom of the disease, and requires further exploration. The causes of brain iron dyshomeostasis in Parkinson s and Alzheimer s disease are speci c to each disorder. Secondary events after onset show both similarities and di erences in each disease. In both cases, imbalance of iron levels could be a contributing factor to the disease and the symptoms. Ideally, therapeutic strategies would inhibit or block both processes. As brain iron homeostasis is restored, reduced iron-induced toxicity should result. is is a challenging task because these diseases are initiated by multiple events, including aging, and are fuelled by several pathways. Iron dyshomeostasis is one pathway in this continuum of events that holds therapeutic promise and requires focused investigation.
5. C. e passage suggests that each of the following was used to determine the relationship between species EXCEPT species diversity. Relationships (Cause E ect) You should nd evidence for each of the three wrong answers. e author discusses several ways to determine relationships between species. e passage starts by discussing DNA and physical characteristics (line 2). Eliminate (A). Even though there are di culties in using fossil records for squamates, line 21 clearly indicates that it has been used in the past. Eliminate (D). e focus of the passage is on behavioral observations, so the author clearly believes observational studies are useful. Eliminate (B). Species diversity is not discussed in the passage, except by saying that species can be di erent. Answer choice (C) is correct. e author is most likely to believe the next logical study on the evolution of Squamates should focus on 6. F. complete observation of squamates in their natural habitat. Author s Voice and Method e author believes observational studies should be integrated into the study of the evolution of Squamates. He emphasizes this in the nal paragraph, saying current research illustrates the potential for a deeper understanding of the evolutionary history of snakes through continued observation (lines 97 99). In order to get accurate results, truly natural behavior must be observed. Answer choice (F) is correct. 7. e purpose of the second paragraph (lines 11 19) is to establish the need for further studies of Squamata species. D. Main Idea e second paragraph discusses the past research involving Squamate evolution and some mistaken conceptions that scientists held. Because of the mistakes and their corrections, the author is indicating that work on the evolutionary history of squamates should continue. Answer choice (D) is correct. 8. J. According to the rst paragraph snakes, lizards, and iguanas share a common ancestor. Generalization e author uses snakes, lizards, and iguanas in his example about evolution. All use the same toxins in their venom, so he concludes that the evolution of venom must have occurred before the three groups separated into distinct families (lines 7 9). If there was a time before the three were distinct families, it is reasonable to conclude they once had a common ancestor. Answer choice (J) is correct. 9. B. What does the passage state is a di culty of behavioral observation? Observational records of snakes in captivity can be incomplete. Details e nal paragraph talks about the di culties associated with behavioral observations. After listing several examples, the author states that without a complete and comprehensive system of observation, the data will be incomplete (lines 95 97). Answer choice (B) is correct.
10. J. e word ubiquitous (line 64) as used in the passage most nearly means common. Meaning of Words e sentence tells you that this behavior is ubiquitous to all vipers, so you must determine what this behavior is. Reviewing the previous few sentences, you can see that this behavior is referring to combat methods. e paragraph tells you that all vipers engage in combat similarly (line 60). Ubiquitous is referring to a behavior that is similar. e closest match to that is common. Answer choice (J) is correct.
1. e main purpose of this passage is to: A. challenge the idea that iron levels are irrelevant to diseases. B. argue that further study on the role of iron in several diseases is needed. C. suggest that curing iron dyshomeostasis would cure either Parkinson s or Alzheimer s or both. D. explain why iron is one of the most important metals in use in the brain. 2. e passage states that traditional studies of iron dyshomeostasis in Parkinson s or Alzheimer s disease suggest: F. iron dyshomeostasis a ects the symptoms of the disease. G. iron dyshomeostasis occurs after cell death. H. treatment of iron dyshomeostasis results in an abatement of symptoms. J. iron accumulates in amyloid plaques in the brain. 3. One di erence between Parkinson s and Alzheimer s disease, according to the passage, is: A. there is an increase in iron regulating proteins in one, but not the other. B. one disease has a single cause, the other has multiple causes. C. iron dyshomeostasis a ects the progression of one, but not the other. D. the area of iron accumulation in is known in one, but not the other. 4. 5. Each of the following is described as a possible source of iron dyshomeostasis EXCEPT: A. B. C. D. 6. As used in line 16, the word stability most nearly means: F. G. H. J. consistency. permanence. strength. immovability. 7. It can be inferred from the passage that prior to this passage, studies had already been conducted on each of the following EXCEPT: A. methods of treating iron dyshomeostasis in Alzheimer s patients. B. iron levels in the brains of Parkinson s patients. C. when iron accumulation in Alzheimer s occurs. D. the result of treating iron accumulation in Parkinson s patients. 8. According to the passage: F. iron dyshomeostasis is one of the most important factors in the development of Parkinson s disease. G. once the causes of iron dyshomeostasis are known, treatment of Alzheimer s and Parkinson s disease will be relatively straightforward. H. Alzheimer s and Parkinson s diseases are the only diseases that involve iron dyshomeostasis. J. the mechanism of iron dyshomeostasis in Alzheimer s is unclear. e main point of the fourth paragraph (lines 38 48) most clearly is to: F. explain that the onset of Alzheimer s and Parkinson s disease both display an increase in iron-regulating proteins. G. discuss reasons why iron levels are impacted throughout both Alzheimer s and Parkinson s disease. H. suggest that treatment of iron levels in Alzheimer s and Parkinson s disease should be a priority. J. describe the complex sources of iron dyshomeostasis for both Alzheimer s and Parkinson s disease. accumulation of iron in amyloid plaques. malformation of iron-regulatory proteins loss of dopamine-producing neurons. disruption of a protein pathway. 9. e sixth paragraph (lines 65 76) suggests that: A. the accumulation of iron in Parkinson s disease should be further studied. B. the e ect of losing dopamine-producing neurons is unclear. C. the causes of brain iron dyshomeostasis in Parkinson s and Alzheimer s disease are di erent. D. treatment of iron dyshomeostasis in Parkinson s patients has unknown results.
1. e main purpose of this passage is to: A. challenge the idea that iron levels are irrelevant to diseases. B. argue that further study on the role of iron in several diseases is needed. C. suggest that curing iron dyshomeostasis would cure either Parkinson s or Alzheimer s or both. D. explain why iron is one of the most important metals in use in the brain. 2. e passage states that traditional studies of iron dyshomeostasis in Parkinson s or Alzheimer s disease suggest: F. iron dyshomeostasis a ects the symptoms of the disease. G. iron dyshomeostasis occurs after cell death. H. treatment of iron dyshomeostasis results in an abatement of symptoms. J. iron accumulates in amyloid plaques in the brain. 3. One di erence between Parkinson s and Alzheimer s disease, according to the passage, is: A. there is an increase in iron regulating proteins in one, but not the other. B. one disease has a single cause, the other has multiple causes. C. iron dyshomeostasis a ects the progression of one, but not the other. D. the area of iron accumulation in is known in one, but not the other. 4. 5. Each of the following is described as a possible source of iron dyshomeostasis EXCEPT: A. B. C. D. 6. As used in line 16, the word stability most nearly means: F. G. H. J. consistency. permanence. strength. immovability. 7. It can be inferred from the passage that prior to this passage, studies had already been conducted on each of the following EXCEPT: A. methods of treating iron dyshomeostasis in Alzheimer s patients. B. iron levels in the brains of Parkinson s patients. C. when iron accumulation in Alzheimer s occurs. D. the result of treating iron accumulation in Parkinson s patients. 8. According to the passage: F. iron dyshomeostasis is one of the most important factors in the development of Parkinson s disease. G. once the causes of iron dyshomeostasis are known, treatment of Alzheimer s and Parkinson s disease will be relatively straightforward. H. Alzheimer s and Parkinson s diseases are the only diseases that involve iron dyshomeostasis. J. the mechanism of iron dyshomeostasis in Alzheimer s is unclear. e main point of the fourth paragraph (lines 38 48) most clearly is to: F. explain that the onset of Alzheimer s and Parkinson s disease both display an increase in iron-regulating proteins. G. discuss reasons why iron levels are impacted throughout both Alzheimer s and Parkinson s disease. H. suggest that treatment of iron levels in Alzheimer s and Parkinson s disease should be a priority. J. describe the complex sources of iron dyshomeostasis for both Alzheimer s and Parkinson s disease. accumulation of iron in amyloid plaques. malformation of iron-regulatory proteins loss of dopamine-producing neurons. disruption of a protein pathway. 9. e sixth paragraph (lines 65 76) suggests that: A. the accumulation of iron in Parkinson s disease should be further studied. B. the e ect of losing dopamine-producing neurons is unclear. C. the causes of brain iron dyshomeostasis in Parkinson s and Alzheimer s disease are di erent. D. treatment of iron dyshomeostasis in Parkinson s patients has unknown results.
10. e author would be most likely to agree with the idea that: F. iron dyshomeostasis is an area of research that has real-world implications. G. there have been failures on the part of researchers studying Parkinson s and Alzheimer s diseases. H. stabilizing iron levels in Parkinson s and Alzheimer s diseases should be the sole priority of further research into those diseases. J. once the causes of iron dyshomeostasis are known, treatment of Parkinson s and Alzheimer s disease will likely be straightforward.
Passage 2 Write in whether you got each problem right or wrong (or left it blank). If your answer was correct, put a 1 in every blank to the right of that problem. Sum up each column and compare your total to the total possible Out Of points in each column. Right/ Wrong/Blank Main Ideas/ Author s Approach Problem Correct Answer 1 B 2 G 3 D 4 H 5 C 6 F 7 A 8 J 9 A 10 F Relationships Meanings Generalizations of Words Total Out Of Details 2 10 3 1 1 3
Passage 2 Solution 1. B. e main purpose of this passage is to argue that further study on the role of iron in several diseases is needed. Main Idea Alzheimer s and Parkinson s diseases are not fully understood, despite the fact that iron plays a signi cant role in each. roughout the passage, the author discusses the impact iron might have and the fact that more study is needed. Answer choice (B) is correct. Answer choice (A) can be eliminated because the author never suggests that researchers think iron levels are irrelevant. e author never goes so far as to say that xing the iron dyshomeostasis would cure the diseases, so eliminate (C). e author certainly thinks iron is important, but never compares it to other metals. e point of the passage is not to compare, but just to explain. Eliminate (D). e passage states that traditional studies of iron dyshomeostasis in Parkinson s or Alzheimer s disease suggest 2. G. iron dyshomeostasis occurs after cell death. Details Lines 34 37 tell you that traditional studies of these disorders suggest that iron accumulation occurs after cell death. Answer choice (G) is correct. 3. D. One di erence between Parkinson s and Alzheimer s disease, according to the passage, is the area of iron accumulation in is known in one, but not the other. Relationships (Comparisons) Paragraphs ve and six are the only areas of the passage that discuss Parkinson s and Alzheimer s di erences. Alzheimer s is framed in paragraph ve, while Parkinson s is six. Eliminate (A) because both disorders increase iron(line 52). Similarly, both have multiple causes, though this is not explained until the nal paragraph; these diseases are initiated by multiple events (lines 85 86). Eliminate answer choice (B). Both are diseases are in this passage because iron dyshomeostasis is relevant. Eliminate (C). Where the iron accumulates, however, is unknown in Parkinson s. What causes the elevation and where the iron accumulates is unclear (lines 69 70). However, in Alzheimers, it is know that iron accumulates in amyloid plaques (lines 53 55). Answer choice (D) is correct. 4. H. e main point of the fourth paragraph (lines 38 48) most clearly is to suggest that treatment of iron levels in Alzheimer s and Parkinson s disease should be a priority. Author s Voice and Method e fourth paragraph is primarily a list of pieces of evidence that indicate iron dyshomeostasis is a critical component of disease progression (lines 40 41). All that evidence supports a reconsideration of the idea discussed in the previous paragraph; that treatment of iron levels should NOT be a priority (lines 36 37). One way to phrase the point of the fourth paragraph is to say that treatment should be a priority. Answer choice (H) is correct.
5. C. Each of the following is described as a possible source of iron dyshomeostasis EXCEPT loss of dopamine-producing neurons. Details e three wrong answers are discussed as sources of iron dyshomeostasis. In Alzheimer s disease, iron accumulates in amyloid plaques (lines 53 54) and iron-regulatory proteins are malformed (lines 59 60), so eliminate (A) and (B). In general, dyshomeostasis can occur when a particular protein or protein pathway is disrupted (lines 22 23), so eliminate (D). Loss of dopamine-producing neurons is associated with Parkinson s disease, but the passage never says this loss contributes to iron dyshomeostasis. Answer choice (C) is correct. 6. F. As used in line 16, the word stability most nearly means consistency. Meaning of Words e paragraph de nes both homeostasis and dyshomeostasis. You learn that when cellular homeostasis is achieved, iron levels are stable (lines 14 15). Lack of stability (line 16) is the oppositeit is associated with dyshomeostasis. You can infer, in this context, stability means the iron levels are constant. Answer choice (F) is correct. 7. A. It can be inferred from the passage that prior to this passage, studies had already been conducted on each of the following EXCEPT methods of treating iron dyshomeostasis in Alzheimer s patients. Generalization Each of the three wrong answers can be reasonably inferred from the passage. You ll have to nd each one. Answer choice (B) comes from lines 67 69; studies have invariably shown that there are also signi cantly elevated levels of iron in the brain [in Parkinson s patients]. You also know that for both diseases, iron levels are clearly impacted throughout the disorder (lines 44 45). Eliminate (C). Finally, treatment of iron dyshomeostasis is discussed, but only for Parkinson s disease. Treatment of iron accumulation results in a reduction of Parkinson s symptoms (lines 72 73). Answer choice (A) is correct. 8. J. According to the passage the mechanism of iron dyshomeostasis in Alzheimer s is unclear. Details ough much is known about the iron levels in Alzheimer s disease, lines 63 64 explain that a full understanding of the underlying mechanism is lacking. Answer choice (J) is correct. 9. A. studied. e sixth paragraph (lines 65 76) suggests that the accumulation of iron in Parkinson s disease should be further Generalization Because iron dyshomeostasis treatment has been shown to reduce Parkinson s symptoms, the author suggests that accumulation of iron in Parkinson s is an active process and requires further exploration (lines 74 76). Answer choice (A) is correct.
10. F. e author would be most likely to agree with the idea that iron dyshomeostasis is an area of research that has real-world implications. Generalizations e author believes that iron dyshomeostasis plays a vital role in several diseases. At the end of the passage, he summarizes this belief by saying iron dyshomeostasis is one pathway in the continuum of events that holds therapeutic promise and requires focused investigation (lines 87 89). Answer choice (F) is correct.