2. 外语
  3. Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behavi

Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behavi

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问题 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.
The primary purpose of the passage is to
选项 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
答案B
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.
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