单细胞生物

Multi tool use
生命演化历程
查 • 论 • 编
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时间轴以百万年为单位
生物可以根据构成的細胞數目分爲单细胞生物和多细胞生物。单细胞生物只由单个细胞组成,而且经常会聚集成为细胞集落。單細胞生物能獨立完成新陳代謝及繁殖等活動。
地球上最早的生物大約在距今35億至41億年前形成,原核生物是最原始的生物,如細菌和藍綠藻且是在溫暖的水中發現。
单细胞生物包括所有古细菌和真细菌和很多原生生物。根据旧的分类法有很多动物,植物和真菌多是单细胞生物。变形虫算作单细胞动物,它的一些种类却算作粘菌,带鞭毛的鞭毛虫如眼虫有时被归为单细胞藻类或者是单细胞动物。新的分类法中,所有的真核单细胞生物都算作原生生物。
粘菌根据最近的研究认为可以独立成界,虽然他们在正常情况下为单细胞,但其直径大小可达80厘米。它可以勉强被归到真菌中,因为它们也会呈现出类似变形虫的状态。
单或多细胞生物的分类只是描述性的,并不能提供任何亲缘、新陈代谢、构造和习性方面的信息。
参見
外部连結
Einzeller Video[永久失效連結]
- 单细胞植物和单细胞动物的区别
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