Evrimin belli kurallar\u0131 var m\u0131d\u0131r? E\u011fer, \u00fcnl\u00fc evrimsel biyolog Stephen Jay Gould\u2019un deyi\u015fiyle, hayat\u0131n ak\u0131\u015f\u0131 ba\u015fa sar\u0131lsayd\u0131, belli biyolojik e\u011filimler yine ortaya \u00e7\u0131kar m\u0131yd\u0131? Di\u011fer t\u00fcrl\u00fc soral\u0131m: Evrim tahmin edilebilir mi?<\/p>\n
Son ara\u015ft\u0131rmalara g\u00f6re, en az\u0131ndan biyolojik v\u00fccut \u00f6l\u00e7\u00fcleri baz al\u0131nd\u0131\u011f\u0131nda, cevap evet. V\u00fccut \u00f6l\u00e7\u00fcs\u00fcn\u00fcn evrimsel geli\u015fimi \u00fczerine bug\u00fcne kadar yap\u0131lan en kapsaml\u0131 ara\u015ft\u0131rmaya g\u00f6re, Stanford \u00dcniversitesi biliminsanlar\u0131, Cope kural\u0131n\u0131 destekleyecek sonu\u00e7lar elde etti. Buna g\u00f6re, hayvan nesli giderek daha b\u00fcy\u00fck bir v\u00fccuda evriliyor.<\/p>\n
Stanford \u00dcniversitesi Evren, Enerji ve \u00c7evre Bilimleri B\u00f6l\u00fcm\u00fc\u2019nden Paleobiyolog Jonathan Payne\u2019in ifadesiyle, \u201cYa\u015fam\u0131n ilk ortaya \u00e7\u0131k\u0131\u015f\u0131ndan ya da ilk hayvanlar\u0131n evriminden beri, \u015fu anda d\u00fcnya \u00fczerinde ya\u015fayan en b\u00fcy\u00fck organizmalar\u0131n art\u0131k var olmayan eski b\u00fcy\u00fck organizmalardan daha b\u00fcy\u00fck olduklar\u0131n\u0131 bir s\u00fcredir biliyorduk.\u201d<\/p>\n
Fakat kesin olmayan \u015fey, hayvanlar\u0131n ortalama b\u00fcy\u00fckl\u00fc\u011f\u00fcn\u00fcn zaman i\u00e7inde de\u011fi\u015fmesinin v\u00fccut b\u00fcy\u00fckl\u00fcklerinin evrimi a\u00e7\u0131s\u0131ndan genel bir e\u011filim g\u00f6sterip g\u00f6stermedi\u011fiydi.\u00a0 Payne\u2019e g\u00f6re, \u201cBu durumu sadece ya\u015fayan organizmalar \u00fczerinden g\u00f6remezsiniz. E\u011fer k\u0131sa d\u00f6nemli g\u00f6zlemler \u00fczerinden \u00e7\u0131kar\u0131mlar yaparsan\u0131z, b\u00fcy\u00fck ihtimalle orant\u0131lar\u0131 ve y\u00f6nelimleri g\u00f6zden ka\u00e7\u0131r\u0131rs\u0131n\u0131z.\u201d<\/p>\n
Science<\/em> dergisinde yay\u0131mlanan \u00e7al\u0131\u015fmaya g\u00f6re, son 542 milyon y\u0131lda deniz hayvanlar\u0131n\u0131n b\u00fcy\u00fckl\u00fc\u011f\u00fc 150 kat artt\u0131. \u0130lk hayvan fosilinin ait oldu\u011fu 550 milyon \u00f6ncesine k\u0131yasla, hayvanlarda v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fcn\u00fcn art\u0131yor olmas\u0131 b\u00fct\u00fcn hayvan nesillerinde aral\u0131ks\u0131z bir b\u00fcy\u00fcme anlam\u0131na gelmiyor. Halihaz\u0131rda b\u00fcy\u00fck olan organizmalar\u0131n \u00e7e\u015fitlili\u011finin daha \u00e7ok artm\u0131\u015f oldu\u011funa i\u015faret ediyor Payne, \u201cBu bizim daha \u00f6nce bilmedi\u011fimiz bir \u015feydi. Hen\u00fcz tam olarak sebebini bilmedi\u011fimiz bir \u015fekilde b\u00fcy\u00fck v\u00fccutlular daha fazla t\u00fcrsel \u00e7e\u015fitlilik g\u00f6sterdi\u201d diyor.<\/p>\n Evrensel bir e\u011filime mi i\u015faret ediyor? <\/strong><\/p>\n Ad\u0131n\u0131 19. y\u00fczy\u0131l\u0131n \u00fcnl\u00fc paleontolo\u011fu Edward Cope\u2019tan alan Cope kural\u0131na g\u00f6re, karada ya\u015fayan at gibi memelilerin b\u00fcy\u00fckl\u00fc\u011f\u00fc zamanla artm\u0131\u015ft\u0131. Biliminsanlar\u0131 bu kural\u0131 di\u011fer hayvanlarda da test etmek istedi. Fakat sonu\u00e7 karma\u015f\u0131kt\u0131. Mercanlar ve dinozorlar\u0131n Cope kural\u0131na uygun bir \u015fekilde b\u00fcy\u00fckl\u00fckleri artm\u0131\u015fken, ku\u015flar ya da b\u00f6ceklerin b\u00fcy\u00fckl\u00fckleri artmam\u0131\u015ft\u0131. Bunun sonucunda kimi biliminsanlar\u0131, bu durumun evrimsel bir olgu mu yoksa rastlant\u0131sal bir durum mu oldu\u011funu sorgulamaya ba\u015flad\u0131. Payne ve ekibi ise Cope kural\u0131n\u0131 b\u00fct\u00fcn deniz hayvanlar\u0131n\u0131 i\u00e7erecek \u015fekilde test etmeye koyuldu. Bu ba\u011flamda fosil kay\u0131tlar\u0131ndaki deniz hayvanlar\u0131n\u0131n y\u00fczde 75\u2019ini ve \u015fimdiye kadar ya\u015fam\u0131\u015f olan deniz hayvanlar\u0131n\u0131n y\u00fczde 60\u2019\u0131n\u0131 kapsayan bir veri k\u00fcmesi olu\u015fturdular. Sonunda bir \u00f6r\u00fcnt\u00fc ortaya \u00e7\u0131km\u0131\u015ft\u0131; ara\u015ft\u0131r\u0131lan t\u00fcrlerin hepsinin v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fc artm\u0131yordu; halihaz\u0131rda b\u00fcy\u00fck olan hayvanlar\u0131n \u00e7e\u015fitlili\u011fi daha \u00e7ok art\u0131yordu. Ekip, su alt\u0131nda b\u00fcy\u00fck olman\u0131n getirdi\u011fi daha h\u0131zl\u0131 hareket etme, daha derin s\u0131\u011f\u0131naklar kazma ve daha b\u00fcy\u00fck avlar avlayabilme avantajlar\u0131n\u0131n bu durumda etkili oldu\u011funu d\u00fc\u015f\u00fcn\u00fcyor.<\/p>\n","protected":false},"excerpt":{"rendered":" Evrimin belli kurallar\u0131 var m\u0131d\u0131r? E\u011fer, \u00fcnl\u00fc evrimsel biyolog Stephen Jay Gould\u2019un deyi\u015fiyle, hayat\u0131n ak\u0131\u015f\u0131 ba\u015fa sar\u0131lsayd\u0131, belli biyolojik e\u011filimler yine ortaya \u00e7\u0131kar m\u0131yd\u0131? Di\u011fer t\u00fcrl\u00fc soral\u0131m: Evrim tahmin edilebilir mi? Son ara\u015ft\u0131rmalara g\u00f6re, en az\u0131ndan biyolojik v\u00fccut \u00f6l\u00e7\u00fcleri baz al\u0131nd\u0131\u011f\u0131nda, cevap evet. V\u00fccut \u00f6l\u00e7\u00fcs\u00fcn\u00fcn evrimsel geli\u015fimi \u00fczerine bug\u00fcne kadar yap\u0131lan en kapsaml\u0131 ara\u015ft\u0131rmaya g\u00f6re, […]<\/p>\n","protected":false},"author":551,"featured_media":21377,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[171,19,21,32],"tags":[200,776,449],"class_list":["post-21376","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-134-sayi","category-bilim-gundemi","category-biyoloji","category-evrim","tag-evrim","tag-hayvanlar","tag-memeliler"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t