GGR305H1 Lecture 6: The Great American Exchange & Intro to Human Emergence (1)
13 May 2016
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Document Summary
Life into the present: mammals: intro to the quaternary. Mammals: when cenozoic started was huge opportunity for mammal evolution. Rise of reptilian precursors after kt extinction. A lot of reptiles survived: massive adaptive radiation of mammals occurring at beginning of cenozoic. Massive increase of species from single stem group: cenozoic can be considered as era of mammals. Early mammals evolved ~220 mya ago, pangea: evolved from therapsids in permian era. Oldest fossil: megazostrodon, rat like creature, had characteristics of early mammals, egg-laying but had ability to produce milk, wasn"t quite reptile but not quite mammal. Was also massive adaptive radiation in jurassic: radical change in body shapes occurring at high rate, mammals (including ancestors of marsupials and placentals) But most mammals came up in cenozoic. 3 major groups: placentals (us): 20 orders. Can carry their young to term (later stage of development) Have larger opening to pelvis because give birth when baby is larger: marsupials: 7 orders.
