动物学绪论(3)

动物学参考资料

到细胞是生物发展的第二个阶段。初期的细胞是原核细胞，由原核细胞构成的生物称为原核生（细菌、蓝藻），从原核到真核是生物发展的第三个阶段，从单细胞真核生物到多细胞真核生物是生物发展的第四个阶段。五界系统反映了生物进化的三个阶段和多细胞生物阶段的三个分支、即原核生物代表了细胞的初级阶段，进化到原生生物代表了真核生物的单细胞阶段（细胞结构的高级阶段）再进化到真核多细胞阶段即植物界、真菌界和动物界。植物真菌和动物代表了进化的三个方向，即自养、腐生和异养。

Developing stages of life and classification of kingdoms

目前人们对生物的分界尚无统一的意见，但从化石记录和地球上现生存生物的形态比较、生理、生化等方面的例证看，揭示了生物从原核到真核，从简单到复杂，从低等到高等的进化方向，生物分界则显示了生物进化发展的历程。

一些基本概念：

原核生物（Prokaryocyte）： A single-celled organism in which the cell lucks a true nucleus and the DNA is present as a loop in the cytoplasm rather than as chromosomes bounded by a nuclear membrane. The prokaryotes comprise the bacteria, which appear in the fossil record more than 3000 Ma ago and are the oldest forms of life known, and the cyanobacteria, known from slightly younger rocks.

真核生物（Eukaryocyte）：An organism comprising cells that have a distinct nucleus enveloped by a double membrane, and other features including double-membraned mitochondria and 80s ribosomes in the fluid of the cytoplasm (i. e. all protists, fungi, plants and animals). The first eukaryocytes were almost certainly green algae.

自养（Autotrophism）与自养生物（Autotrophic organism）：An organism that uses carbon dioxide as its main or sole source of carbon.

腐生（Pythogenesis）与腐生生物 （Saprophagous organism）：Any organisms that absorbs soluble organic nutrients from inanimate sources (e. g. from dead plants or animal matter, etc.).

动物学参考资料

异养（Allotrophy）与异养生物（Heterotroph）：An organism that is unable to manufacture its own food from simple chemical compounds and therefore consumes other organisms, living or dead, as its main or sole source of carbon.

2、动物的定义及在生物界的种类比例

动物是生物界的消费者。构成生物界的主体，现存种类约占生物界的78%。

Chief differnces between plants and animals

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