什么是原生动物
任何微小的(常常在显微镜下才能观察到的)单细胞原生生物。它们在大多数土壤、乾净的水和海洋中都可见到。大多数是单独存在的个体,但也有不同的群居物种。原生动物之间以及原生动物和原生生物之间在分类学上的关系时常被改动。最小的已知原生动物是小於2微米的小型血液寄生虫,而最大的则可能有16厘米长,能被肉眼看见。原生动物在形态变化上有差别,但都有一些共同的真核生物特点,如都有油性蛋白质的膜和带膜的液泡及细胞器官(参阅eucaryote)。它们在活动方式、营养和生殖上的差别很大。在原生动物的分类上存在不同的分类系统。主要的门包括肉鞭门(带鞭毛的和带延展细胞质,即伪足)、纤毛门(带纤毛的)、顶覆门、微孢子门和黏体动物门(能产生孢子的)。顶覆门和微孢子门常常被包括在简单的孢子亚门中。常见的原生动物包括腰鞭毛虫、阿米巴和草履虫(参阅Paramecium)。
protozoan
Any of a group of small (usually microscopic) single-celled protists. They are found worldwide in most soils, fresh water, and oceans. While most are solitary individuals, various colonial forms exist. The taxonomic relationships of protozoans to one another and to other protists continue to be revised. The smallest known protozoans are tiny blood parasites less than 2 microns long; the largest may be 16 mm long and visible to the naked eye. Protozoan shapes vary, but all share such eukaryotic features as lipid-protein membranes and membrane-enclosed vacuoles and organelles (see eukaryote). They show wide variation in modes of movement, nutrition, and reproduction. Various classification systems exist to group the protozoans. The major phyla include Sarcomastigophora (flagellated forms and forms possessing cytoplasmic extensions called pseudopodia), Ciliophora (ciliated forms), and Apicomplexa, Microspora, and Myxozoa (spore-producing forms). Apicomplexa and Microspora are sometimes included in the single phylum Sporozoa. Commonly known protozoans include dinoflagellates, amoebas, and paramecia (see paramecium).
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穷途之哭是什么意思?
意思是:因车无路可行而悲伤,后指处于困境所发的绝望的哀伤。成语名字:穷途之哭成语发音:qióngtúzhīkū成语解释:因车无路可行而悲伤,后指处于困境所发的绝望的哀伤。成语出处:《晋书阮籍传》:“时率意独驾,不由径路,车迹所穷,辄痛哭而返。”成语繁体:窮途之哭感情色彩:中...
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桑中之喜是什么意思?
意思是:谓男女不依礼法的结合。成语名字:桑中之喜成语发音:sāngzhōngzhīxǐ成语解释:谓男女不依礼法的结合。成语出处:春秋·鲁·左丘明《左传·成公二年》:“申叔跪从其父,将适郢,遇之,曰:‘异哉!夫子有三军之惧,而又有桑中之喜,宜将窃妻以逃者也。’”感情色彩:中性成语...
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一如既往是什么意思?
意思是:指态度没有变化;完全像从前一样。一:完全;如:像;既往:从前。成语名字:一如既往成语发音:yīrújìwǎng成语解释:指态度没有变化;完全像从前一样。一:完全;如:像;既往:从前。成语出处:《第二次握手六》:“清末以来,到海外求学的中国人何止千百,在学业上有成就的也大有人在,可...
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燕市悲歌是什么意思?
意思是:《史记·刺客列传》:“荆轲既至燕,爱燕之狗屠及善击筑者高渐离。荆轲嗜酒,日与狗屠及高渐离饮于燕市,酒酣以往,高渐离击筑,荆轲和而歌于市中,相乐也,已而相泣,旁若无人者。”后以“燕市悲歌”表现朋友间的情谊以及惜别的情怀。成语名字:燕市悲歌成语发音:yànshìb...