推荐回答(5个)
常见的无脊椎动物有:
1、原生动物,如草履虫、变形虫等单细胞动物。
原生动物门(Protozoa)是动物界的1门,为最原始、最简单、最低等的动物。
2、腔肠动物,如水螅、海葵、海蜇等。
刺胞动物门(Cnidaria)又称刺细胞动物门,过去称为腔肠动物门(Coelenterata),因为它的含义适用于刺胞动物及栉水母动物,所以现多已废弃不用;刺胞动物体呈辐射或两辐射对称,仅具二胚层,是最原始的后生动物。
3、扁形动物,如涡虫、绦虫、血吸虫等。
扁形动物门是动物界的一个门,无脊椎动物,是一类两侧对称,三胚层,无体腔,无呼吸系统、无循环系统,有口无肛门的动物。
4、线形动物,如蛔虫、线虫等。
Nemathelminthes 旧称“圆形动物门”,动物界的一门。大部分为小形的蠕形动物,体通常呈长圆柱形,两端尖细,不分节,具原体腔,消化道不弯曲,前端为口,后端为肛门,雌雄异体。
5、环节动物,如蚯蚓、沙蚕等。
环节动物门(学名:Annelida)在动物进化上发展到一个较高的阶段,是高等无脊椎动物的开始,约有9,000种。体外有由表皮细胞分泌的角质膜,体壁有一外环肌层和一内纵肌层。通常有几丁质的刚毛,按节排列。

扩展材料:
地球上无脊椎动物的出现至少早于脊椎动物1亿年。大多数无脊椎动物化石见于古生代寒武纪,当时已有节肢动物的三叶虫及腕足动物。随后发展了古头足类及古棘皮动物的种类。到古生代末期,古老类型的生物大规模绝灭。
中生代还存在软体动物的古老类型(如菊石),到末期即逐渐绝灭,软体动物现代属、种大量出现。到新生代演化成现代类型众多的无脊椎动物,而在古生代盛极一时的腕足动物至今只残存少数代表(如海豆芽)。
参考资料:百度百科-无脊椎动物
无脊椎动物大多自由生活。在水生的种类中,体小的营浮游生活;身体具外壳的或在水底爬行(如虾、蟹),或埋栖于水底泥沙中(如沙蚕蛤类),或固着在水中外物上(如藤壶、牡蛎等)。无脊椎动物也有不少寄生的种类,寄生于其他动物、植物体表或体内(如寄生原虫、吸虫、绦虫、棘头虫等)。有些种类如蚓蛔虫和猪蛔虫等可给人类带来危害。
无脊椎动物
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