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CAMBRIAN EXPLOSION  ~542 million years

The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around 530 million years ago, as evidenced by the fossil record .

This was accompanied by a major diversification of other organisms, including animals, phytoplankton, and calcimicrobes. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 or 80 million years the rate of evolution accelerated by an order of magnitude (as defined in terms of the extinction and origination rate of species) and the diversity of life began to resemble today’s.

The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the mid 19th century, and Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection.

The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin and evolution of animals. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures left in Cambrian rocks. (click to see all the article on Wikipedia)

寒武紀生命大爆發 ~542百萬年前

寒武紀生命大爆發,或稱寒武紀生命輻射,約在53千萬年前發生,從化石紀錄可得知,大多數的複雜生物大群,似乎在此時迅速地出現。

(譯者註:major groups 主要群體,指的是大的分類項目,找了生物界分類,group不在分類中,無從對應過去,有錯請指正。)

這爆發帶來了一個大量的,其他生物的多樣性,包含了動物,浮游植物和鈣鹽微生物。在58千萬年前,大多數生物的構造都是簡單的,只是任意的單細胞偶然地組成了群體。之後的7千萬或8千萬年,進化的比率加速到一個數量級之快(從物種滅絕與誕生這兩方面的比率來定義),生命的多樣性看起來就如同今日的狀態。

(譯者註:1.calcimicrobes 沒找到中文翻譯,我是把字拆成兩部份翻的,正確性完全不知XD 2.一個數量級:有好幾種,2,10,10^3,2^10,一般來說是10 3.看來這式子應該是:物種誕生/物種滅絕)

寒武紀生命大爆發引發了許多的科學辯論。早在19世紀中葉就被注意到的原始地層,裡頭的化石似乎是突然出現的。查爾斯.達爾文認為這個地層,是其中一個可以用來駁斥他的天擇演化論的主要的反對意見。

有關於寒武紀動物群似乎是突然且憑空出現,這懸而未決的謎團,問題集中在以下三點:在寒武紀初期,是否真有大量的複雜生物多樣化,能夠在一段相對較短的時期產生?是發生了什麼,使得變動如此迅速?有關於動物的起源與進化,這又代表了什麼?只依靠有限的證據,像是不完全的化石紀錄和寒武紀岩石留存下來的化學特徵,是很難解釋這謎團的。

(維基連結:寒武紀大爆發)

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