BCOR 12 1st Edition Lecture 19Outline of Last Lecture I. Shared Derived Characters of ChordatesII. CephalochordatesIII. TunicatesIV. VertebratesV. GnathostomesVI. Bony FishVII. TetrapodsOutline of Current Lecture I. AmphibiansII. Amniotic Egg EvolutionIII. SauropsidsIV. MammalsV. HumansCurrent LectureAmphibians- 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 exchangeAmniotic Egg EvolutionThese 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 yolko Advantage: enables animals to complete their life cycle on land- Amniotes – tetrapods that have a terrestrial adapted amniotic eggSauropsids = reptilesShared Derived Characters:I. Scales made of keratinII. Lay shelled eggsIII. 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 metabolismMammals- 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 outII. Hair – great insulation layerIII. Larger brainsIV. Differentiated teeth for an omnivorous diet- Primates are about 55-57 million years oldHumans = 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 chimpsShared Derived Characters:I. Upright posture and bipedal locomotiona. Advantage: freed our handsII. Larger brainsIII. Manufacture and use of complex toolsIV. Shortened jawV. Shorter digestive tract- Oldest hominin fossil is 6.5 million years oldTrends in Hominin evolution:I. Emergence of bipedalismII. 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
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