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生命進化史

出自維基百科,自由嘅百科全書

生命進化史粵拼sang1 ming6 zeon3 faa3 si2)係指地球上嘅生命進化嘅歷史。

地球係目前宇宙已知行星入面唯一能夠維持生命嘅[1]。一般認為大約 40 億年前嘅高能化學反應產生咗能夠複製自己嘅分子,打後 5 億年就出現咗所有生命嘅共同祖先,再分化咗細菌古菌出嚟[2]。早期嘅生命體發展出搞光合作用嘅能力,於是有得直接利用太陽能向大氣嗰度釋放啲氧氣。大氣度積累嘅氧氣俾太陽射嘅紫外線作用,喺上層大氣形成咗臭氧(O3),出現咗臭氧層[3]。早期嘅生命以原核生物(以單一原核細胞組成嘅生物)嘅形態存在。由於臭氧層吸收咗太陽射落嚟嘅紫外線,陸地變到好啱生命生存,所以生命開始喺陸地上面繁衍[4]。目前已知最早嘅生命化石證據有西澳洲砂岩入面揾到嘅 34.8 億年前嘅微生物墊化石[5][6][7][8]、西格陵蘭變質碎屑岩度 37 億年前嘅生源石墨[9]、仲有西澳洲岩石度 41 億年前嘅生物質殘骸[10]

距離而家大約 5.42 億年前發生咗寒武紀生命大爆發(Cambrian explosion)。由化石睇,嗰時地球上嘅多細胞生物種類突然之間多咗好多,包括節肢動物三葉蟲奇蝦[11]。化石記錄顯示大多數嘅動物都係喺呢個時期出現嘅[12][13]。呢個時期持續咗大約 2 千萬年至 2 千 5 百萬年,導致咗大多數現代動物門嘅發散。複雜啲嘅生物多咗好多,生物多樣性大幅噉提高,所以佢俾人話係生命嘅大爆發。

喺後少少嘅 5 億年前嘅奧陶紀(Ordovician)地球有咗脊椎動物甲冑魚。打後嘅化石記錄顯示地球又有咗幾次生物物種嘅大規模增加或者滅絕[14],最近嗰次係 6 千 6 百萬年前嘅白堊紀-第三紀滅絕事件(Cretaceous–Paleogene extinction event),呢次事件引致咗恐龍嘅滅絕,但係一啲細隻嘅動物-當中有哺乳類-走得甩死唔去,令到地球嘅生命持續落去。嗰次之後,哺乳類開始變到愈嚟愈發達,而幾百萬年前嘅非洲嘅類動物似乎開始用兩隻腳行,空咗對手出嚟令到佢哋可以整工具,個又變到愈嚟愈大-慢慢進化成智人(Homo sapien)[15]。智人嘅各種活動產生咗世界嘅各大文明科技

各種猿類動物(包括人)嘅骨骼

引述

[編輯]
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