学生问到：海豚是不是鱼类

海豚是鱼类动物

海豚 Delphinidae;dolphins 海豚属于哺乳纲、鲸目、齿鲸亚目，海豚科，通称海豚，共有近62种，分布于世界各大洋。体长1.2～4.2米，体重23～225千克。海豚一般嘴尖，上下颌各有约100颗尖细的牙齿，主要以小鱼、乌贼、虾、蟹为食。 海豚喜欢过“集体”生活，少则几头，多则几百头。海豚是一种本领超群、聪明伶俐的海中哺乳动物。经过训练，能打乒乓球、跳火圈等。除人以外，海豚的大脑是动物种最发达的。人的大脑占本人体重的百分之二点一，海豚的大脑占它体重的百分之一点七。海豚的大脑由完全隔开的两部分组成，当其中一部分工作时，另一部分充分休息，因此，可终生不眠。 海豚是靠回声定位来判断目标的远近、方向、位置、形状、甚至物体的性质。有人做试验，把海豚的眼睛蒙上，把水搅浑，它们也能迅速、准确的追到扔给它的食物。 海豚不但有惊人的听觉，还有高超的游泳和异乎寻常的潜水本领。据有人测验，海豚的潜水记录是300米深，而人不穿潜水衣，只能下潜20米。至于它的游泳速度，更是人类比不上的。 海豚的速度可达每小时40公里，相当于鱼雷快艇的中等速度。
海豚是不是鱼类

海豚是哺乳动物

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　　烟草中的尼古丁会引起动脉收缩，传奇世界私服
热血江湖私服
天龙八部私服传奇世界私服减少流向阴道的血液流量。生殖器官由于血流量的减少而变得不敏感，使性唤起和达到性高潮产生障碍。专家指出，解决这一问题的惟一方法就是戒烟。

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