在讲“鱼纲”一节时，我让学生准备了三条鲫鱼，教学生把第一条鲫鱼的胸鳍和腹鳍剪掉放入鱼缸甲观察，这条鱼会因失去保持鱼体平衡运动的器官，腹面时常上翻；第二条鲫鱼剪去尾鳍保留胸鳍和腹鳍，放入鱼缸乙中，这条鱼因失去保持鱼体前进方向的运动器官，只能缓缓而行；第三条 In the section on “The Fish School”, I asked the students to prepare three squid. The students cut off the pectoral and pelvic fins of the first squid and put it in the aquarium A. This fish would lose its organ to keep the fish balanced. The second side of the carp cuts off the caudal fins to keep the pectoral and pelvic fins, and puts them into the fish tank B. This fish can only move slowly due to the loss of the moving organs that keep the fish moving in the forward direction;