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一.引言在初中动物学课本中有这样一段:“家鸽的呼吸器官有一特点,就是肺脏跟许多气囊相通,气囊是鸟类所特有的一种构造,由薄膜组成,用以贮存气体。气囊分布在体腔内的各器官之间,有些气囊分布在皮肤下和骨的内部,气囊对鸟类的生活有很大的意义。它们能够减轻鸟体的体重,保持体温和促进呼吸。”为了使这段描述有强烈地说明力,就必须让学生
I. INTRODUCTION In the textbook of junior high school zoology, there is a passage like this: “There is a characteristic of the pigeon’s respiratory organs that the lungs communicate with many air sacs that are unique to birds and are made of thin films for gas storage. Distributed among various organs in the body cavity, some of the air cells are distributed both under the skin and inside the bones, and the airbags have great significance for the life of the birds. They can reduce body weight, maintain body temperature and promote breathing. ”In order to make This description has a strong explanatory power, it must be for students