{"id":15377,"date":"2016-06-01T16:55:55","date_gmt":"2016-06-01T13:55:55","guid":{"rendered":"http:\/\/109.232.216.219\/~bilimvegelecek\/?p=15377"},"modified":"2017-12-27T17:00:25","modified_gmt":"2017-12-27T14:00:25","slug":"yasamin-evriminde-1-milyar-yil-onceki-sicramanin-isaretleri","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2016\/06\/01\/yasamin-evriminde-1-milyar-yil-onceki-sicramanin-isaretleri","title":{"rendered":"Ya\u015fam\u0131n evriminde 1 milyar y\u0131l \u00f6nceki s\u0131\u00e7raman\u0131n i\u015faretleri"},"content":{"rendered":"<p>\u00c7in\u2019den gelen kan\u0131tlara g\u00f6re, ya\u015fam 1 milyar y\u0131l \u00f6ncesinden daha erken bir zamanda geni\u015f h\u00fccre topluluklar\u0131 halinde organize olmu\u015ftu. Santimetre \u00f6l\u00e7e\u011findeki ya\u015fam formlar\u0131, \u00fclkenin kuzeyindeki Yanshan b\u00f6lgesinde \u00e7amur ta\u015f\u0131nda korunmu\u015ftur ve bu formlar\u0131n 1,56 milyar y\u0131l \u00f6ncesine ait oldu\u011fu tespit edilmi\u015ftir. \u00c7\u0131plak g\u00f6zle g\u00f6r\u00fclebilecek b\u00fcy\u00fckl\u00fckte olan fosiller, 635 ila 541 milyon y\u0131l \u00f6ncesinde yayg\u0131nla\u015fm\u0131\u015ft\u0131. Ancak en son analiz edilen \u00f6rneklerin, bu d\u00f6nemden iki kat\u0131 a\u015fan bir s\u00fcre \u00f6ncesinde oldu\u011fu g\u00f6sterilmi\u015ftir. Bulgular, \u00c7inli-Amerikal\u0131 ara\u015ft\u0131rmac\u0131lardan olu\u015fan bir ekip taraf\u0131ndan <em>Nature Communications<\/em> dergisinde yay\u0131mland\u0131.<\/p>\n<p>Gaoyuzhuang kaya olu\u015fumundaki gizemli organizmalar\u0131n, g\u00fcn\u00fcm\u00fczde tekh\u00fccreli amipten bitki, mantar ve hayvanlara kadar her \u015feyi i\u00e7eren \u00f6karyotik ya\u015fam dal\u0131na ait oldu\u011fu d\u00fc\u015f\u00fcn\u00fcl\u00fcyor. Denizde bulunan ya\u015fam formlar\u0131, muhtemelen eski okyanuslar\u0131n s\u0131\u011f b\u00f6lgelerinde ya\u015fam\u0131\u015flard\u0131 ve alglerle y\u00fczeysel bir benzerli\u011fe sahiptiler. Onlar\u0131n bitkilerin, baz\u0131 bakterilerin ve di\u011fer basit organizmalar\u0131n g\u00fcne\u015f \u0131\u015f\u0131\u011f\u0131n\u0131 kimyasal enerjiye d\u00f6n\u00fc\u015ft\u00fcrmelerine ili\u015fkin i\u015flem olan fotosentez olay\u0131n\u0131 da ger\u00e7ekle\u015ftirdikleri anla\u015f\u0131lmaktad\u0131r.<\/p>\n<p>\u00c7al\u0131\u015fman\u0131n yazarlar\u0131ndan, Harvard \u00dcniversitesi\u2019nden Prof. Andrew Knoll, bu organizmalar\u0131n b\u00fcy\u00fck boyutta oldu\u011funu, ancak karma\u015f\u0131k olduklar\u0131 konusunda ku\u015fku duydu\u011funu ifade ediyor.<\/p>\n<p>Knoll, \u201c\u0130nsan, 250 h\u00fccre tipi, d\u00fczinelerce doku ve farkl\u0131 organ sistemine sahip oldu\u011fu i\u00e7in karma\u015f\u0131k \u00e7okh\u00fccreli bir organizman\u0131n iyi bir \u00f6rne\u011fidir. Di\u011fer taraftan, sahile giderseniz, hemen hemen ayn\u0131 h\u00fccre katman\u0131ndan olu\u015fan deniz yosunlar\u0131 g\u00f6r\u00fcrs\u00fcn\u00fcz. Bu h\u00fccre tabakalar\u0131n\u0131n \u00e7o\u011fu, ya fotosentez yapabilmektedir ya da \u00fcreme i\u00e7in fayda sa\u011flayabilmektedirler\u201d diyor.<\/p>\n<p>Prof. Knoll ve \u00c7in Jeolojik Ara\u015ft\u0131rmalar\u2019dan Shixing Zhu\u2019yu i\u00e7eren ekip, bu eski zaman periyotlar\u0131nda bulunan ya\u015fam\u0131n, \u00f6nceki \u00e7e\u015fitli formlardan geli\u015fti\u011fini d\u00fc\u015f\u00fcn\u00fcyor.<\/p>\n<figure id=\"attachment_15379\" aria-describedby=\"caption-attachment-15379\" style=\"width: 300px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-15379\" src=\"https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc-300x226.jpg\" alt=\"\" width=\"300\" height=\"226\" srcset=\"https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc.jpg 300w, https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc-80x60.jpg 80w, https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc-100x75.jpg 100w, https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc-180x135.jpg 180w, https:\/\/bilimvegelecek.com.tr\/wp-content\/uploads\/2017\/12\/1-milyon-y\u0131l-\u00f6nce-ya\u015fam-formlar\u0131-b\u00fcy\u00fcd\u00fc-238x178.jpg 238w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><figcaption id=\"caption-attachment-15379\" class=\"wp-caption-text\">Fosilleri i\u00e7eren kayalar, uranyum-kur\u015fun y\u00f6ntemiyle tarihlendirilmi\u015f.<\/figcaption><\/figure>\n<p>Bulunan 53 ayr\u0131 fosil \u00f6rne\u011finin 26\u2019s\u0131 (y\u00fczde 49\u2019u) lineer \u015fekle sahipken, 16\u2019s\u0131 (y\u00fczde 30\u2019u) kama (takoz) \u015feklinde, 8\u2019i (y\u00fczde 15\u2019i) dil \u015feklinde ve 3\u2019\u00fc (y\u00fczde 6\u2019s\u0131) ise dikd\u00f6rtgen \u015feklinde. Deniz organizmalar\u0131n\u0131n uzunluklar\u0131n\u0131n 30 cm ve geni\u015fliklerinin 8 cm\u2019ye kadar oldu\u011fu \u00f6l\u00e7\u00fclm\u00fc\u015f. \u00d6rneklerin bir k\u0131sm\u0131 yap\u0131y\u0131 ortaya \u00e7\u0131kar\u0131yor. Bu yap\u0131, pamuk lifleriyle ayn\u0131 geni\u015flikte ve yakla\u015f\u0131k 10 mikrometre uzunlukta oldu\u011fu \u00f6l\u00e7\u00fclen bireysel h\u00fccrelerin s\u0131k\u0131ca paketlenmi\u015f bir d\u00fczenlemesi.<\/p>\n<p>1,5 milyardan daha erken bir tarihte \u00e7okh\u00fccreli ya\u015fam\u0131n \u00f6rneklerine daha \u00f6nce rastlanm\u0131\u015ft\u0131. \u00d6rne\u011fin tespih gibi \u015fekillenen <em>Horodyskia<\/em> ve sarmal, kurdele benzeri bir organizma olan <em>Grypania<\/em> gibi. Ancak, Yanshan\u2019daki fosiller \u015fekil ve boyut \u00e7e\u015fitlili\u011fine sahip.<\/p>\n<p>Ara\u015ft\u0131rmac\u0131lar, fosillerin mikrobiyal d\u00fc\u011f\u00fcm olarak adland\u0131r\u0131lan bakteri k\u00fcmeleri olmalar\u0131n\u0131n m\u00fcmk\u00fcn olmad\u0131\u011f\u0131n\u0131 ifade ediyor. Bunun yerine, \u00f6karyotik organizmalar\u0131n muhtemel ilk \u00f6rnekleri oldu\u011funu d\u00fc\u015f\u00fcn\u00fcyorlar. E\u011fer b\u00f6yleyse, bu organizmalardan yola \u00e7\u0131k\u0131larak, ba\u015flang\u0131c\u0131 542 milyon y\u0131l \u00f6nce olan, b\u00fcy\u00fck canl\u0131 gruplar\u0131n\u0131n ortaya \u00e7\u0131kmas\u0131yla sonu\u00e7lanan ve h\u0131zl\u0131 bir evrimsel olay olan Kambriyen patlamas\u0131ndan bir milyar y\u0131l kadar \u00f6nce \u00e7okh\u00fccrelili\u011fin ba\u015flad\u0131\u011f\u0131n\u0131 ve bunun denizsel ya\u015fam\u0131n bir \u00f6zelli\u011fi oldu\u011fu \u00f6neriliyor.<\/p>\n<p>Baz\u0131 biliminsanlar\u0131 bu durumu, tart\u0131\u015fmal\u0131 bir konu olmas\u0131na kar\u015f\u0131n, evrimsel y\u00fckselmenin k\u0131smen de olsa oksijen d\u00fczeyindeki bir art\u0131\u015fla ilintili olu\u015funa yoruyor. Bulgular ayr\u0131ca, d\u00fc\u015f\u00fck oksijen d\u00fczeyi ile karakterize edilen ve bazen \u201cs\u0131k\u0131c\u0131 milyar y\u0131l\u201d olarak ifade edilen \u00f6nceki \u00e7a\u011f\u0131n yanl\u0131\u015f de\u011ferlendirilmi\u015f olabilece\u011fini de g\u00fcndeme getiriyor.<\/p>\n<p>Prof. Knoll BBC\u2019ye \u015fu a\u00e7\u0131klamay\u0131 yapt\u0131: \u201cG\u00f6receli \u015fartlarda tekh\u00fccreliden basit \u00e7okh\u00fccreli organizmaya do\u011fru olan s\u0131\u00e7rama kolay gibi g\u00f6z\u00fckmektedir. Evrim s\u00fcreci boyunca bir\u00e7ok kez bu ger\u00e7ekle\u015fmi\u015f olabilir; bulgular\u0131m\u0131z ger\u00e7ekten \u00f6karyotlar\u0131n tarihinin erken bir zaman oldu\u011fu g\u00f6r\u00fc\u015f\u00fcn\u00fc peki\u015ftiriyor. Hem tekh\u00fccreli organizmalar hem de onlara en yak\u0131n \u00e7okh\u00fccreli akrabalar\u0131n\u0131n genomlar\u0131 ile ilgili bildi\u011fimiz iki durum vard\u0131r. Bunlardan biri, tekh\u00fccreliden basit \u00e7okh\u00fccreli bir canl\u0131ya do\u011fru olan s\u0131\u00e7rama ger\u00e7ekle\u015fti\u011finde, bunun organizman\u0131n gen i\u00e7eri\u011finde \u00e7ok k\u00fc\u00e7\u00fck farkl\u0131l\u0131klara yol a\u00e7t\u0131\u011f\u0131d\u0131r. Bunun k\u00fc\u00e7\u00fck bir s\u0131\u00e7rama oldu\u011funu s\u00f6yleyebiliriz. Buna kar\u015f\u0131n, basit \u00e7okh\u00fccreli bir canl\u0131dan karma\u015f\u0131k \u00e7okh\u00fccreli bir canl\u0131ya ge\u00e7i\u015fteki farkl\u0131l\u0131k olduk\u00e7a b\u00fcy\u00fckt\u00fcr. Ya\u015fam a\u011fac\u0131 bunun sadece nadiren meydana geldi\u011fini ileri s\u00fcrmektedir.\u201d<\/p>\n<p>Bununla birlikte ekip, ya\u015fayan ya da yok olmu\u015f olan di\u011fer bilinen \u00f6karyotik gruplarla bu fosilleri birbirine ba\u011flayamam\u0131\u015ft\u0131r.<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u00c7in\u2019den gelen kan\u0131tlara g\u00f6re, ya\u015fam 1 milyar y\u0131l \u00f6ncesinden daha erken bir zamanda geni\u015f h\u00fccre topluluklar\u0131 halinde organize olmu\u015ftu. Santimetre \u00f6l\u00e7e\u011findeki ya\u015fam formlar\u0131, \u00fclkenin kuzeyindeki Yanshan b\u00f6lgesinde \u00e7amur ta\u015f\u0131nda korunmu\u015ftur ve bu formlar\u0131n 1,56 milyar y\u0131l \u00f6ncesine ait oldu\u011fu tespit edilmi\u015ftir. \u00c7\u0131plak g\u00f6zle g\u00f6r\u00fclebilecek b\u00fcy\u00fckl\u00fckte olan fosiller, 635 ila 541 milyon y\u0131l \u00f6ncesinde yayg\u0131nla\u015fm\u0131\u015ft\u0131. Ancak [&hellip;]<\/p>\n","protected":false},"author":866,"featured_media":15378,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[185,19,21,32],"tags":[200,816,488,595],"class_list":["post-15377","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-148-sayi","category-bilim-gundemi","category-biyoloji","category-evrim","tag-evrim","tag-fosil","tag-organizma","tag-yasam"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/15377","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/users\/866"}],"replies":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/comments?post=15377"}],"version-history":[{"count":0,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/posts\/15377\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/media\/15378"}],"wp:attachment":[{"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/media?parent=15377"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/categories?post=15377"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bilimvegelecek.com.tr\/index.php\/wp-json\/wp\/v2\/tags?post=15377"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}