{"id":5635,"date":"2020-01-13T22:44:42","date_gmt":"2020-01-13T22:44:42","guid":{"rendered":"https:\/\/course.oeru.org\/eths101\/?page_id=5635"},"modified":"2020-01-13T22:44:42","modified_gmt":"2020-01-13T22:44:42","slug":"mass-extinctions","status":"publish","type":"page","link":"https:\/\/course.oeru.org\/eths101\/learning-pathways\/ecology-and-evolution\/mass-extinctions\/","title":{"rendered":"Mass Extinctions"},"content":{"rendered":"<div id=\"content\" class=\"mw-body container\" role=\"main\">\n<div class=\"row\">\n<div class=\"col-md-12\">\n<div class=\"panel\">\n<div class=\"panel-body\">\n<div id=\"bodyContent\">\n<div id=\"mw-content-text\" lang=\"en\" dir=\"ltr\" class=\"mw-content-ltr\">\n<p>In this Learning Pathway,  we learn that extinction is one path of evolution. It is normal &#8211; extinctions have been happening throughout time. The fossil record tells us that life has diversified since complex organisms first evolved some 600 million years ago. But over that time life has been through the nexus of five major mass extinction events and several smaller ones. We also look at what a mass extinction is and examine two case studies: the &#8216;Great Dying&#8217; at the end of the Permian (252 million years ago) and the iconic demise of the Dinosaurs at the end of the Cretaceous 66 million years ago.\n<\/p>\n<div class=\"center\">\n<div class=\"floatnone\"><a href=\"https:\/\/wikieducator.org\/File:Bleachedcoral.jpg\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"Bleachedcoral.jpg\" src=\"\/\/wikieducator.org\/images\/thumb\/2\/21\/Bleachedcoral.jpg\/420px-Bleachedcoral.jpg\" width=\"420\" height=\"315\" class=\"img-responsive\"><\/a><\/div>\n<\/div>\n<div class=\"panel iDevice\">\n\t<div class=\"panel-heading idevice-heading\">\n\t\t<div>\n\t\t\t<img decoding=\"async\" class=\"pedagogicalicon\" alt=\"key point\" src=\"https:\/\/course.oeru.org\/eths101\/wp-content\/themes\/oeru_course\/idevices\/Icon_key_points.png\">\n\t\t<\/div>\n\t\t<div>\n\t\t\t<h2>Questions to keep in mind<\/h2>\n\t\t<\/div>\n\t<\/div>\n\t<div class=\"panel-body\">\n\t\t<div class=\"col-md-12\">\n\t\t\t<\/p>\n<ol>\n<li>What is a mass extinction?\n<\/li>\n<li>What events trigger a mass extinction?\n<\/li>\n<li>The case studies described all pre-date the advent of humans. Actually, insights from today are informing many of our interpretations of the past. You might like to contemplate what humans are doing in terms of Earth systems? Are we changing things in ways that mimic natural extreme conditions that coincided with these dramatic events in the history of life? This is something we will discuss as part of the full unit of Learning at UTAS.\n<\/li>\n<\/ol>\n<p>\n<\/p>\n<p>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n<p>\n<\/p>\n<p>\nExtinction is a normal part of evolution. When species are exposed to conditions (including the presence of competitors, predators and pathogens) beyond their tolerances, are unable to move anywhere that suits them and cannot evolve fast enough they will become extinct.\n<\/p>\n<ul>\n<li> Humans or Homo sapiens are the only Hominid to still exist. Over the last 5 million years of evolution of this family, there have been rapid changes and experiments that did not continue. Anatomically modern humans are the only group to be extant (still around) and the many other branches of the human family tree are extinct.\n<ul>\n<li>This will take to you to an <a rel=\"nofollow\" class=\"external text\" href=\"http:\/\/humanorigins.si.edu\/evidence\/human-family-tree\">Interactive human family tree<\/a>. The site will help you explore the different human-like species that didn&#8217;t evolve fast enough.\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<div class=\"center\">\n<div class=\"floatnone\"><a href=\"https:\/\/wikieducator.org\/File:Ape_skeletons.png\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"Ape skeletons.png\" src=\"\/\/wikieducator.org\/images\/thumb\/4\/49\/Ape_skeletons.png\/420px-Ape_skeletons.png\" width=\"420\" height=\"228\" class=\"img-responsive\"><\/a><\/div>\n<\/div>\n<p>\n<\/p>\n<ul>\n<li>Island inhabitants are vulnerable to extinction. Dodos were once abundant on the Island of Mauritius. They were first described by European sailors in the late 1500s. The birds were painted, written about, collected and hunted for food. Within 60 years they were extinct. Humans caused the extinction of the dodos, birds which are now synonymous with extinction.\n<\/li>\n<\/ul>\n<p>\n<\/p>\n<p>\n<\/p>\n<div class=\"center\">\n<div class=\"floatnone\"><a href=\"https:\/\/wikieducator.org\/File:Dronte_17th_Century.jpg\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"Dronte 17th Century.jpg\" src=\"\/\/wikieducator.org\/images\/thumb\/5\/57\/Dronte_17th_Century.jpg\/420px-Dronte_17th_Century.jpg\" width=\"420\" height=\"522\" class=\"img-responsive\"><\/a><\/div>\n<\/div>\n<h1><span class=\"mw-headline\" id=\"Extinctions_at_scale\">Extinctions at scale<\/span><\/h1>\n<div class=\"thumb tright\">\n<div class=\"thumbinner thumbnail\" style=\"width:182px\"><a href=\"https:\/\/wikieducator.org\/File:Phillipsfig4.gif\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" src=\"\/\/wikieducator.org\/images\/thumb\/9\/97\/Phillipsfig4.gif\/180px-Phillipsfig4.gif\" width=\"180\" height=\"262\" class=\"thumbimage img-responsive\"><\/a>  <\/p>\n<div class=\"thumbcaption\">Curve of LIfe<\/div>\n<\/div>\n<\/div>\n<p>In his curve of life, John Phillips recognised that there were times when the fossil record became sparse. These times are co-incident with the disappearance of many different forms of life in a relatively short span of geological time. We call the largest of these events mass extinctions.\n<\/p>\n<p><br style=\"clear:both\">\n<\/p>\n<p>\n<\/p>\n<p>\nThe graph below depicts thousands of marine genera plotted through geological time. It is apparent that the number of genera is increasing through time. This may partially be an artefact of fossil preservation, which is better in more recent successions. The graph is based on a compendium of fossil data from nearly 300 locations that included 36,380 genera made by J. Sepkoski (2002).<br \/>\nImportantly, the graph also shows times when the number of genera dropped dramatically. The largest drops are arrowed in yellow and others are in blue. The drops marked with yellow arrows are the five major mass extinction events. Because of the change in fossil types across these time spans, they also coincide with major geological period or era boundaries.\n<\/p>\n<div class=\"center\">\n<div class=\"floatnone\"><a href=\"https:\/\/wikieducator.org\/File:Phanerozoic_Biodiversity.svg\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"Phanerozoic Biodiversity.svg\" src=\"\/\/wikieducator.org\/images\/thumb\/4\/4d\/Phanerozoic_Biodiversity.svg\/600px-Phanerozoic_Biodiversity.svg.png\" width=\"600\" height=\"355\" class=\"img-responsive\"><\/a><\/div>\n<\/div>\n<div class=\"panel iDevice WEquizMultipleChoice\">\n\t<div class=\"panel-heading idevice-heading\">\n\t\t<div>\n\t\t\t<img decoding=\"async\" class=\"pedagogicalicon\" alt=\"assessment\" src=\"https:\/\/course.oeru.org\/eths101\/wp-content\/themes\/oeru_course\/idevices\/Icon_qmark.png\">\n\t\t<\/div>\n\t\t<div>\n\t\t\t<h2>Mass Extinction and geological Time scale<\/h2>\n\t\t<\/div>\n\t<\/div>\n\t<div class=\"panel-body\">\n\t\t<div class=\"col-md-12\">\n\t\t\t\n<p>Select one of the following\n<\/p>\n<p>\n<\/p>\n<ul>\n<li> What major era change at around 250 million years ago is associated with the &#8220;Great Dying&#8221;, the largest mass extinction event?\n<ul>\n<li> Mesozoic to Cenozoic\n<ul>\n<li> <b>Incorrect<\/b>.  Try again, this period represents the period 66 million years ago. It marks the end of the dinosaurs.\n<\/li>\n<\/ul>\n<\/li>\n<li> Ordovician to the Silurian\n<ul>\n<li> <b>Incorrect<\/b>. The end of the Ordovician to the Silurian.\n<\/li>\n<\/ul>\n<\/li>\n<li> Paleozoic to Mesozoic\n<ul>\n<li> <b>Correct<\/b>.  Yes, the &#8220;Great Dying&#8221; is at the boundary between &#8220;old Life&#8221; the Paleozoic era and &#8220;middle life&#8221; the Mesozoic era.\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\n<\/p>\n<p>\n\t\t<\/div>\n\t<\/div>\n<\/div><\/p>\n<p>\n<\/p>\n<h2><span class=\"mw-headline\" id=\"5_Major_Mass_Extinctions\">5 Major Mass Extinctions<\/span><\/h2>\n<ol>\n<li>End of the <b>Ordovician<\/b> Period\n<\/li>\n<li>End of the <b>Devonian<\/b> Period\n<\/li>\n<li>End of the <b>Permian<\/b> Period\n<\/li>\n<li>End of the <b>Triassic<\/b> Period\n<\/li>\n<li>End of the <b>Cretaceous<\/b> Period\n<\/li>\n<\/ol>\n<div class=\"center\">\n<div class=\"floatnone\"><a href=\"https:\/\/wikieducator.org\/File:Geologic_time_scale.jpg\" class=\"image\"><img loading=\"lazy\" decoding=\"async\" alt=\"Geologic time scale.jpg\" src=\"\/\/wikieducator.org\/images\/thumb\/2\/22\/Geologic_time_scale.jpg\/420px-Geologic_time_scale.jpg\" width=\"420\" height=\"851\" class=\"img-responsive\"><\/a><\/div>\n<\/div>\n<p>After each major mass extinction event there have been &#8220;reef gaps&#8221;: where it has taken many millions of years before reefs come back. Recently it has been suggested that reefs have come back more rapidly than first thought after the Permian mass extinction event, but these reefs were dominated by sponges &#8211; not coral. In fact this mass extinction wiped out all the older coral forms and it was not until some 10 million years later that a new form of coral evolved and reefs began to reappear in the fossil record.\n<\/p>\n<dl>\n<dt>Disaster Taxa and Recovery<\/dt>\n<dd> A mass extinction may be marked by the abundance of a few resilient groups. These are called disaster taxa. Over time as the environment becomes more stable and favourable for life new opportunities arise for new species to evolve.\n<\/dd>\n<\/dl>\n<p>\n<\/p>\n<div class=\"panel iDevice\">\n\t<div class=\"panel-heading idevice-heading\">\n\t\t<div>\n\t\t\t<img decoding=\"async\" class=\"pedagogicalicon\" alt=\"media\" src=\"https:\/\/course.oeru.org\/eths101\/wp-content\/themes\/oeru_course\/idevices\/Icon_multimedia.png\">\n\t\t<\/div>\n\t\t<div>\n\t\t\t<h2>Mass extinctions and the future of life on Earth<\/h2>\n\t\t<\/div>\n\t<\/div>\n\t<div class=\"panel-body\">\n\t\t<div class=\"col-md-12\">\n\t\t\t<\/p>\n<p>You might like to watch the below TED talk by Michael Benton. He is a well-known palaeontologist who has worked on the end Permian mass extinctions and has research focused on understanding mass extinction in the fossil record. He talks about extinction rates, climate change in mass extinctions and evolutionary risk factors\n<\/p>\n<div class=\"plainlinks center\"><iframe loading=\"lazy\" width=\"425px\" height=\"355px\" src=\"\/\/www.youtube.com\/embed\/envK-qWyDU0?rel=0\" frameborder=\"0\" allowfullscreen=\"\"><\/iframe><\/div>\n<p>\n<\/p>\n<p>\n\t\t<\/div>\n\t<\/div>\n<\/div>\n<p><!-- \nNewPP limit report\nCPU time usage: 0.700 seconds\nReal time usage: 5.522 seconds\nPreprocessor visited node count: 396\/1000000\nPreprocessor generated node count: 1508\/1000000\nPost\u2010expand include size: 10086\/2097152 bytes\nTemplate argument size: 4851\/2097152 bytes\nHighest expansion depth: 8\/40\nExpensive parser function count: 0\/100\n--><\/p>\n<p><!-- Saved in parser cache with key we_en-mw_:pcache:idhash:185158-0!*!*!!*!2!* and timestamp 20200113224434 and revision id 1065352\n -->\n<\/div>\n<div class=\"visualClear\"><\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"row\">\n<div class=\"col-md-12\">\n<ul class=\"pager\">\n<li class=\"previous\">\n            <a href=\"\/eths101\/learning-pathways\/ecology-and-evolution\/-concepts-of-biological-evolution\">\u2190 Previous<\/a>\n          <\/li>\n<li class=\"next\">\n            <a href=\"\/eths101\/learning-pathways\/ecology-and-evolution\/-extinction-at-an-end\">Next \u2192<\/a>\n          <\/li>\n<\/ul><\/div>\n<\/p><\/div>\n<\/div>\n<footer>\n<br \/>\n<\/footer>\n","protected":false},"excerpt":{"rendered":"<p>In this Learning Pathway, we learn that extinction is one path of evolution. It is normal &#8211; extinctions have been happening throughout time. The fossil record tells us that life has diversified since complex organisms first evolved some 600 million years ago. But over that time life has been through the nexus of five major [&hellip;]<\/p>\n","protected":false},"author":155,"featured_media":0,"parent":5625,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-5635","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/pages\/5635","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/users\/155"}],"replies":[{"embeddable":true,"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/comments?post=5635"}],"version-history":[{"count":1,"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/pages\/5635\/revisions"}],"predecessor-version":[{"id":5636,"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/pages\/5635\/revisions\/5636"}],"up":[{"embeddable":true,"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/pages\/5625"}],"wp:attachment":[{"href":"https:\/\/course.oeru.org\/eths101\/wp-json\/wp\/v2\/media?parent=5635"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}