BCOR 12 1st Edition Lecture 19 Outline of Last Lecture I Shared Derived Characters of Chordates II Cephalochordates III Tunicates IV Vertebrates V Gnathostomes VI Bony Fish VII Tetrapods Outline of Current Lecture I Amphibians II Amniotic Egg Evolution III Sauropsids IV Mammals V Humans Current Lecture Amphibians Animals that still rely on water but can live on land Amphibians rely on water for reproduction External reproduction occurs between males and female amphibians During metamorphosis gills turn into lungs Use their skin for gas exchange Amniotic Egg Evolution These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Amniotic egg shelled egg in which an embryo develops within a fluid filled amniotic sac and is nourished by yolk o Advantage enables animals to complete their life cycle on land Amniotes tetrapods that have a terrestrial adapted amniotic egg Sauropsids reptiles Shared Derived Characters I Scales made of keratin II Lay shelled eggs III Are ectothermic except birds which are endothermic Ectothermic body that is warmed by heat generated by an external source sun Endothermic body that is warmed by heat generated by metabolism Mammals Mammals are amniotes that have hair and produce milk Order Mammalia groups I Monotremes lay an egg and secrete milk II Marsupials embryos develop into a sac that secretes milk III Placental mammals have a placenta that nourishes the embryo Shared Derived Characters I Mammary glands where milk comes out II Hair great insulation layer III Larger brains IV Differentiated teeth for an omnivorous diet Primates are about 55 57 million years old Humans mammals that have a large brain and have bipedal locomotion Oldest Homo sapien fossil 160 000 years old Lineage leading to Homo sapiens is 7 million years old Hominin 20 or so now extinct species that are more closely related to humans than to chimps Shared Derived Characters I Upright posture and bipedal locomotion a Advantage freed our hands II Larger brains III Manufacture and use of complex tools IV Shortened jaw V Shorter digestive tract Oldest hominin fossil is 6 5 million years old Trends in Hominin evolution I Emergence of bipedalism II Sophisticated tool use the two are not mutually exclusive III Living socially Hominins walked upright for at least 3 million years Humans evolved in an environment similar to today s East Africa savanna Out of Africa hypothesis the idea that modern humans arose form Homo ergaster descendants in Africa 200 000 years ago
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