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直播课程一 PowerPoint PPT Presentation


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直播课程一. 第四节 软骨鱼纲和硬骨鱼纲. 鱼纲?. 一、上下颌出现的意义. ① . 可以主动摄食,增加了获得食物的机遇; ② . 颌上着生牙齿,便于摄食,同时通过撕咬和研磨,使原来不能直接利用的物质被利用,从而开拓了食物的来源。 ③ . 作为攻击和防御器官,同时还是营巢、求偶、钻洞、呼吸进水等的器官。 ④ . 促进其它器官系统的发展,带动了动物体制结构的全面进化发展。. 二、外部形态. 1 、鳞片及鳞式. 盾鳞 硬鳞 骨鳞:圆鳞、栉鳞. 鳞式:在鱼类分类学上,常把侧线本身和侧线上下方的鳞片数目按一定格式记录下来,作为分类的一种特征依据,就是鳞式。

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直播课程一

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