托福阅读：Behavioral biologists

Behavioral biologists ask two basic types of questions about animal behavior: how animals behave and why they behave as they do. The &6how" questions seek to understand the proximate or immediate causes underlying a behavior at a particular time and place.

　　For example, a biologist might want to explain the singing of a male white-throated sparrow in the spring in terms of hormonal or neural mechanisms. Such physiological causes of behavior are proximate factors. Alte:matively, another biologist might ask what purpose singing serves the sparrow, and then attempt to understand events in the evolution of birds that led to springtime singing. These are "why" questions that focus on ultimate causation, the evolutionary origin and purpose of behavior. These two types of questions are very independent approaches to behavior.

　　Questions about proximate causation examine how animals perform their various functions at the molecular, cellular, organismal, and population levels. The biological sciences that address proximate causes are known as experimental sciences because they use the experimental method of: (1) predicting how a system will respond to a disturbance, (2) making the disturbance, and (3) #paring the observed results with the predictions.

　　Researchers repeat the experimental conditions many times to eliminate chance results that might lead to false conclusions. Questions about ultimate causation ask what produced biological systems and their distinctive properties through evolutionary time. The sciences dealing with ultimate causes are known as evolutionary sciences, and they mainly use the #parative method rather　than experimentation. Researchers #pare characteristics of molecular biology, cell　biology, anatomy, development, and ecology among related species to identify patterns　of variation.

　　Which sentence below best expresses the essential information in the highlighted sentence in paragraph l? Incorrect choices change the meaning in important ways or leave out essential information.

　　A11 questions asked by behavioral biologists fall into two basic categories.

　　Proximate and ultimate causation are distinct ways of thinking about behavior.

　　"Why" questions and questions about ultimate causes require very different methods

　　Behavioral biologists must think very independently about important questions.