阅读理解 Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a "behavioral gene." Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists—specialists in animal behavior—are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly's circadian (24-hour) rhythm, a behavioral gene because flies with mutated per genes are healthy; they simply have different rhythms.

单选题 5.The primary purpose of the passage is to

A、 summarize findings in an area of research
B、 discuss different perspectives on a scientific question
C、 outline the major questions in a scientific discipline
D、 illustrate the usefulness of investigating a research topic
E、 reconcile differences between two definitior's of a term

【正确答案】 B

【答案解析】Main idea
The passage discusses two problems confronting researchers studying the genetic bases of animal behavior: the complexity of the control of most behaviors by multiple genes, and divergence between research fields in what counts as a behavioral gene. The passage focuses mainly on the latter issue, discussing how ethologists define "behavioral gene" in a narrower manner than neuroscientists, who define the term broadly.To elucidate the ethologists' approach, two genes are discussed, one a behavioral gene, the other not.
A The passage primarily aims to explain how researchers in two different research are is define "behavioral gene." It does not try to summarize the research findings of either area.
B Correct. The primary purpose of the passage is to identify differing perspectives on the scientific question of how genes control animal behavior.
C The scientific disciplines of genetics, neuroscience, and ethology—all subdisciplines of biology—contain many different "major questions," and the passage does not try to outline the great variety of such questions in any one of those subdisciplines.
D The topic of the utility of doing research is not part of the passage discussion.
E An important purpose of the passage is to illustrate divergence among scientific fields in how a key term is defined, but the point is to show how the definitions differ rather than to "reconcile" the difference.
The correct answer is B.

单选题 6.The passage suggests that neuroscientists would most likely consider Shaker to be which of the following ?

A、 An example of a behavioral gene
B、 One of multiple genes that control a single behavior
C、 A gene that, when mutated, causes an alteration in a specific normal behavior without making the organism ill
D、 A gene of interest to ethologists but of no interest to neuroscientists
E、 A poor source of information about the nenous system

【正确答案】 A

【答案解析】Application
The passage asserts that ethologists do not regard Shaker as a behavioral gene because it merely makes fruit flies exhibit unhealthy behavior (shaking under anesthesia). But neuroscientists, according to the passage, are mainly interested in how genes, via the nervous system, contribute to behavior. The passage suggests that neuroscientists, unlike ethologists, have no reservation about using the term behavioral gene to apply to any gene that contributes to behavior. The implication is that neuroscientists would probably regard Shaker as a behavioral gene.
A Correct. The passage suggests that neuroscientists would probably regard Shaker as a behavioral gene.
B The passage indicates that research shows Shaker is a sufficient cause, in fruit flies, of shaking under anesthesia. Although some organism might display a behavior controlled by Shaker in concert with other genes, the passage is silent on any such possibility.
C The passage lacks information as to whether there is any alteration—one that neuroscientists would likely consider healthy—in a normal behavior if the alteration is caused by a mutation in Shaker.
D The passage indicates that neuroscientists' interest in genetics is part of their effort to understand the nervous system. This seems to imply that neuroscientists might be interested in Shaker.
E The passage is silent on how neuroscientists would evaluate the potential for Shaker to contribute to understanding of the nervous system.
The correct answer is A.

单选题 7.It can be inferred from the passage that which of the following, if true, would be most likely to influence ethologists' opinions about whether a particular gene in a species is a behavioral gene?

A、 The gene is found only in that species.
B、 The gene is extremely difficult to identify.
C、 The only effect of mutations in the gene is o make the organism ill.
D、 Neuroscientists consider the gene to be a behavioral gene.
E、 Geneticists consider the gene to be a behavioral gene.

【正确答案】 C

【答案解析】Application
The passage identifies two criteria that ethologists use in deciding whether a gene should count as a behavioral gene: a mutation in the gene alters a specific normal behavior and the mutation does not merely make the organism ill.
A The passage is silent on whether either of two genes identified by ethologists in fruit flies are to be found only in fruit flies. The two criteria mentioned used by ethologists carry no implication as to whether any gene unique to a given species would count as a behavioral gene.
B The difficulty of identifying a gene can obviously be due to many factors, such as limitations in existing scientific techniques, and the passage does not imply that such difficulty increases the likelihood that a gene would count as a behavioral gene for ethologists.
C Correct. The passage implies that if this were found to be true, ethologists would regard it as sufficient reason for not counting the gene as a behavioral gene.
D A central theme of the passage is that whether ethologists would count a gene as a behavioral gene is largely unaffected by whether neuroscientists do so, given the divergent perspectives of the scientists' respective disciplines.
E The main contrast in the passage with respect to definitions of the term behavioral gene is between ethologists and neuroscientists, and no specific definitional criteria for this term are explicitly attributed to geneticists. However, there is a slight suggestion that since geneticists find that most behaviors are governed by multiple genes, geneticists might regard any gene involved in the governance of a behavior as a behavioral gene. This approach, however, would be unlikely to influence the opinions of ethologists concerning definition.
The correct answer is C.