一、创设情景,提出问题(教师播放“鱼儿的家”:由河岸上绿色的草、鲜艳的花、高大的树和河里清澈的水、欢快的鱼,转变成河岸上高楼林立、车水马龙,以及河里由一个个排污管道排放的污水和奄奄一息的鱼儿的动画,引导学生发现问题。 First, the creation of scenarios, raise questions (teacher play “fish’s home ”: from the banks of the green grass, bright flowers, tall trees and the clear water of the river, cheerful fish, into a river of high-rise buildings , Busy, and the river by a sewage pipe drainage and dying fish animation, guide students to identify problems.