{"id":35944,"date":"2019-08-19T03:43:21","date_gmt":"2019-08-19T00:43:21","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=35944"},"modified":"2019-08-25T12:46:37","modified_gmt":"2019-08-25T09:46:37","slug":"kambriyen-patlamasi-adlandirmasi-ne-anlatir","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2019\/08\/19\/kambriyen-patlamasi-adlandirmasi-ne-anlatir","title":{"rendered":"Kambriyen Patlamas\u0131 adland\u0131rmas\u0131 ne anlat\u0131r?"},"content":{"rendered":"

D\u00fcnya\u2019n\u0131n yakla\u015f\u0131k 4,5 milyar ya\u015f\u0131nda oldu\u011fundan ve ilk canl\u0131 h\u00fccrelerin 3,5-3,8 milyar y\u0131l \u00f6nce ortaya \u00e7\u0131kt\u0131\u011f\u0131ndan \u015fimdiye dek pek \u00e7ok kez s\u00f6z ettik. \u0130lk organizmalardan sonra gelen 1,6 milyar y\u0131l boyunca, \u00f6karyotlar ortaya \u00e7\u0131k\u0131ncaya kadar, t\u00fcm organizmalar basit yap\u0131da prokaryot h\u00fccrelerdi. G\u00fcn\u00fcm\u00fczden yakla\u015f\u0131k 2 milyar y\u0131l \u00f6nce \u00f6karyot h\u00fccreler ortaya \u00e7\u0131kt\u0131\u011f\u0131nda h\u00fccre yap\u0131s\u0131 daha karma\u015f\u0131kla\u015ft\u0131, ancak organizmalar h\u00e2l\u00e2 tekh\u00fccreliydi ya da h\u00fccre kolonileri halinde ya\u015f\u0131yorlard\u0131. Bu durum yakla\u015f\u0131k 1,4 milyar y\u0131l boyunca, daha karma\u015f\u0131k yap\u0131daki \u00e7okh\u00fccreli Ediacara formlar\u0131n\u0131n ortaya \u00e7\u0131kmas\u0131na kadar devam etti. Buraya kadar s\u00f6ylediklerimizi bir araya getirdi\u011fimizde, ya\u015fam\u0131n D\u00fcnya \u00fczerinde bulundu\u011fu ilk 3 milyar y\u0131l boyunca, evrimin bakteri, plankton ve \u00e7okh\u00fccreli algler d\u0131\u015f\u0131nda \u00e7ok fazla \u00e7e\u015fitlilikte organizmaya yol a\u00e7mad\u0131\u011f\u0131n\u0131 s\u00f6yleyebiliriz. Ancak g\u00fcn\u00fcm\u00fczden yakla\u015f\u0131k 543-490 my\u00f6 (\u00f6zellikle 543-542 my\u00f6), g\u00f6rece olarak k\u0131sa bir zaman diliminde canl\u0131 \u00e7e\u015fitlili\u011finde \u00e7ok h\u0131zl\u0131 bir art\u0131\u015f ya\u015fand\u0131. \u201cKambriyen Patlamas\u0131\u201d ad\u0131 verilen bu olayda, say\u0131s\u0131z yeni canl\u0131 t\u00fcr\u00fc ortaya \u00e7\u0131karak D\u00fcnya\u2019ya yay\u0131ld\u0131.<\/p>\n

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\u015eekil 1: Hayvanlar \u00e2leminin \u00f6nemli kollar\u0131n\u0131n \u00e7o\u011fu Kambriyen D\u00f6nemi\u2019nde ortaya \u00e7\u0131ksa da, bu d\u00f6nemde ortaya \u00e7\u0131kan canl\u0131lar\u0131n \u00f6nemli k\u0131sm\u0131 zaman i\u00e7erisinde ortadan kalkt\u0131 ya da \u00f6nemsizle\u015fti.<\/figcaption><\/figure>\n

Kambriyen Patlamas\u0131 canl\u0131l\u0131k tarihi a\u00e7\u0131s\u0131ndan \u00e7ok \u00f6nemli bir yere sahiptir, \u00e7\u00fcnk\u00fc hayvanlar \u00e2leminin \u00f6nemli kollar\u0131n\u0131n \u00e7o\u011fu fosil kay\u0131tlar\u0131nda ilk defa bu d\u00f6nemde ortaya \u00e7\u0131kt\u0131lar.(\u015eekil1)<\/p>\n

Canl\u0131 \u00e7e\u015fitlili\u011findeki ilk art\u0131\u015f, Ediacara Faunas\u0131 canl\u0131lar\u0131nda g\u00f6r\u00fcl\u00fcyordu (635-542 my\u00f6), bu Kambriyen D\u00f6nemi\u2019nden \u00f6ncesine rastl\u0131yordu. Bu d\u00f6nemde ortaya \u00e7\u0131kan canl\u0131lardan bir k\u0131sm\u0131 g\u00fcn\u00fcm\u00fcze kadar devam eden organizmalarla ba\u011flant\u0131l\u0131yken, bir k\u0131sm\u0131 daha sonra ortadan kayboldu. Ancak Kambriyen D\u00f6nemi ile birlikte, canl\u0131 \u00e7e\u015fitlili\u011finde meydana gelen h\u0131zl\u0131 art\u0131\u015f o zamana kadar g\u00f6r\u00fclmemi\u015f bir seviyeye ula\u015ft\u0131. Bu d\u00f6nemdeki canl\u0131 \u00e7e\u015fitlili\u011fi art\u0131\u015f\u0131n\u0131 Kambriyen Patlamas\u0131 olarak adland\u0131r\u0131yoruz; ama bu adland\u0131rmayla genel olarak, \u00e7ok h\u0131zl\u0131 bir olu\u015fumdan bahsetmiyoruz. \u00d6zellikle baz\u0131 kesitlerde canl\u0131 \u00e7e\u015fitlili\u011findeki art\u0131\u015f \u00e7ok h\u0131zl\u0131 olsa da, \u00f6ncesi ve sonras\u0131 ile 30-70 milyon y\u0131ll\u0131k bir s\u00fcre\u00e7ten s\u00f6z ediyoruz. Gene de canl\u0131lar\u0131n ilk ortaya \u00e7\u0131kt\u0131\u011f\u0131 andan itibaren ge\u00e7en toplam zamana k\u0131yasla, bu kadar k\u0131sa bir zamanda meydana gelen art\u0131\u015f \u201cpatlama\u201d olarak ifade edilebilir.<\/p>\n

Kambriyen D\u00f6nemi\u2019nden g\u00fcn\u00fcm\u00fcze kalan fosil \u00f6rnekleri<\/strong><\/p>\n

Kambriyen Patlamas\u0131 ile ilgili bilgilerimizi, fosil ve jeolojik kay\u0131tlar\u0131n bize izin verdi\u011fi miktarda elde edebiliyoruz. Bilgilerimizin ana kayna\u011f\u0131 fosil kay\u0131tlar\u0131d\u0131r. Daha do\u011frusu, g\u00fcn\u00fcm\u00fcze ula\u015fabilen iyi durumdaki fosillerdir. Elimize ge\u00e7en fosiller, fosille\u015febilen k\u0131s\u0131mlara sahip organizmalardan kalanlard\u0131r. Organizmalar\u0131n, milyonlarca y\u0131l boyunca toprak alt\u0131nda bozulmadan g\u00fcn\u00fcm\u00fcze kadar gelmesi gerekiyor.<\/p>\n

Kambriyen D\u00f6nemi\u2019ni ve \u00f6ncesini birbirinden ay\u0131ran en \u00f6nemli \u00f6zellik, \u00f6nceki d\u00f6nemden kalan korunmu\u015f fosil \u00f6rneklerinin \u00e7ok daha az olmas\u0131d\u0131r. Kambriyen D\u00f6nemi\u2019nde ise fosil kay\u0131tlar\u0131nda h\u0131zl\u0131 bir art\u0131\u015f ya\u015fanm\u0131\u015ft\u0131r. Bu fark\u0131n nedeni, Kambriyen \u00f6ncesi d\u00f6nemde ya\u015fayan organizmalar\u0131n fosille\u015fecek k\u0131s\u0131mlara sahip olmamas\u0131 ya da zaman i\u00e7erisinde fosillerinin yok olmas\u0131d\u0131r. Gene de, 570 milyon y\u0131l \u00f6ncesinden kalma ufak embriyon fosillerinden s\u00f6z edebiliriz. Organizmalar\u0131n bal\u00e7\u0131kta b\u0131rakt\u0131klar\u0131 ve zaman i\u00e7erisinde fosille\u015fen izler de bize dolayl\u0131 yoldan bilgi verir.<\/p>\n

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\u015eekil 2: Kambriyen D\u00f6nemi\u2019nden kalma bir Hallucigenia (eklembacakl\u0131) fosili.<\/figcaption><\/figure>\n

Kambriyen \u00e7e\u015fitlili\u011finin en iyi \u00f6rnekleri Kanada\u2019daki \u201cBurgess Shale\u201d fosil yataklar\u0131nda bulunmu\u015ftur. D\u00f6nemin ortalar\u0131ndan kalan fosiller aras\u0131nda midye benzeri \u201ckolsu ayakl\u0131lar\u201d (brachiopod), trilobitler, yumu\u015fak\u00e7alar, derisi dikenliler (ekinoderm) ve di\u011fer g\u00fcn\u00fcm\u00fczde olmayan bir\u00e7ok garip g\u00f6r\u00fcn\u00fc\u015fl\u00fc hayvan fosili bulunuyor. (\u015eekil 2)<\/p>\n

\u00d6rne\u011fin, be\u015f g\u00f6zl\u00fc ve bir yang\u0131n hortumuna benzeyen burnuyla Opabinia<\/em> ve z\u0131rhl\u0131 yap\u0131s\u0131 ve iki s\u0131ra dik duran pullar\u0131yla Wiwaxia<\/em> d\u00f6nemin garip g\u00f6r\u00fcn\u00fc\u015fl\u00fc hayvanlar\u0131ndand\u0131. (\u015eekil 3) Bilim insanlar\u0131 bu t\u00fcr garip g\u00f6r\u00fcn\u00fc\u015fl\u00fc hayvanlar\u0131n s\u0131n\u0131fland\u0131r\u0131lmas\u0131nda zorluk \u00e7ekseler de, bir k\u0131sm\u0131n\u0131n eklembacakl\u0131lara dahil olduklar\u0131 anla\u015f\u0131l\u0131yor. Ancak Opabinia<\/em> gibi hayvanlar\u0131 bug\u00fcn ya\u015fayan bir gruba dahil etmek zor g\u00f6r\u00fcn\u00fcyor.<\/p>\n

Kambriyen D\u00f6nemi\u2019nin \u00e7evre \u015fartlar\u0131<\/strong><\/p>\n

800-600 my\u00f6 d\u00fcnya \u00e7ap\u0131nda \u201cGe\u00e7 Riphean\u201d ve \u201cErken Vendian\u201d d\u00f6nemlerinde buzlanma olmu\u015ftu, ancak Kambriyen D\u00f6nemi\u2019ne gelinirken zorlu ko\u015fullar art\u0131k sona eriyordu ve s\u0131cakl\u0131k g\u00fcn\u00fcm\u00fczde oldu\u011fundan fazlayd\u0131.<\/p>\n

Karasal yap\u0131 olarak, g\u00fcn\u00fcm\u00fczden 800 my\u00f6, D\u00fcnya \u00fczerinde Rodinia ad\u0131nda tek bir k\u0131ta bulunuyordu. Kambriyen D\u00f6nemi\u2019nin ba\u015flad\u0131\u011f\u0131 d\u00f6nemde ise bu s\u00fcperk\u0131ta par\u00e7alanarak daha k\u00fc\u00e7\u00fck k\u0131talara ayr\u0131lmaya ba\u015flam\u0131\u015ft\u0131.<\/p>\n

D\u00f6nemin temel \u00f6zelliklerine bakt\u0131\u011f\u0131m\u0131zda; t\u00fcm ya\u015fam\u0131n sularda oldu\u011funu, ya\u015fam formlar\u0131n\u0131n \u00e7o\u011funun k\u00fc\u00e7\u00fck yap\u0131larda ve ortaya \u00e7\u0131kan hayvanlar\u0131n \u00e7o\u011funun da s\u0131rad\u0131\u015f\u0131 v\u00fccut yap\u0131lar\u0131nda oldu\u011funu g\u00f6r\u00fcr\u00fcz.<\/p>\n

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\u015eekil 3: Kambriyen D\u00f6nemi\u2019nin garip canl\u0131lar\u0131ndan Opabinia (solda) ve Wiwaxia (sa\u011fda).<\/figcaption><\/figure>\n

Kambriyen Patlamas\u0131\u2019n\u0131n nedenleri ne olabilir?<\/strong><\/p>\n

Bilim insanlar\u0131, bu kadar k\u0131sa bir zaman diliminde ortaya \u00e7\u0131kan bu derece farkl\u0131 v\u00fccut yap\u0131lar\u0131n\u0131n nedeni olarak farkl\u0131 a\u00e7\u0131klamalar getiriyor. \u00d6ncelikle g\u00fcn\u00fcm\u00fczden 700 my\u00f6 ba\u015flayan oksijen art\u0131\u015f\u0131 hareket i\u00e7in bir yak\u0131t kayna\u011f\u0131 olu\u015fturmu\u015f ve karma\u015f\u0131k v\u00fccut yap\u0131lar\u0131n\u0131n ortaya \u00e7\u0131kmas\u0131na neden olmu\u015f olabilir. Di\u011fer bir neden de Kambriyen D\u00f6nemi \u00f6ncesinde meydana gelen kitlesel yok olu\u015f sonras\u0131, yeni t\u00fcrler i\u00e7in ekolojik bir bo\u015flu\u011fun a\u00e7\u0131lmas\u0131d\u0131r. Bir di\u011fer neden de, geli\u015fimle ilgili genlerin Kambriyen D\u00f6nemi \u00f6ncesinde ge\u00e7irdikleri evrimsel geli\u015fme olabilir.<\/p>\n

Kaynak: <\/strong>Deniz \u015eahin, 50 Soruda Ya\u015fam\u0131n Tarihi, Bilim ve Gelecek Kitapl\u0131\u011f\u0131, Ekim 2011, 2. Bask\u0131, s.168-171<\/p>\n","protected":false},"excerpt":{"rendered":"

D\u00fcnya\u2019n\u0131n yakla\u015f\u0131k 4,5 milyar ya\u015f\u0131nda oldu\u011fundan ve ilk canl\u0131 h\u00fccrelerin 3,5-3,8 milyar y\u0131l \u00f6nce ortaya \u00e7\u0131kt\u0131\u011f\u0131ndan \u015fimdiye dek pek \u00e7ok kez s\u00f6z ettik. \u0130lk organizmalardan sonra gelen 1,6 milyar y\u0131l boyunca, \u00f6karyotlar ortaya \u00e7\u0131k\u0131ncaya kadar, t\u00fcm organizmalar basit yap\u0131da prokaryot h\u00fccrelerdi. G\u00fcn\u00fcm\u00fczden yakla\u015f\u0131k 2 milyar y\u0131l \u00f6nce \u00f6karyot h\u00fccreler ortaya \u00e7\u0131kt\u0131\u011f\u0131nda h\u00fccre yap\u0131s\u0131 daha karma\u015f\u0131kla\u015ft\u0131, […]<\/p>\n","protected":false},"author":429,"featured_media":35945,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3624],"tags":[5163,200,816,5161,5162,2872],"class_list":["post-35944","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-sorularla-bilim","tag-ediacara","tag-evrim","tag-fosil","tag-kambriyen","tag-opabinia","tag-yasamin-tarihi"],"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