BSC 116 Lecture Notes - Lecture 19: Homo Erectus, Neanderthal, Homo Ergaster

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Lecture 19: amniotes & the evolution of terrestrial vertebrates part ii. Mammals radiated after the dinosaurs went extinct: primates is one mammal order: the one we belong to, human evolution over the last 6-7 my has been complex. Early synapsids reptilian: e. g. , dimetrodon: no hair, splayed legs, laid eggs, nearly wiped out by end-permian extinction. Mammary glands (and other traits) diagnose modern mammals. Mammals can be recognized by a number of traits: mammary glands that produce milk, hair and subcutaneous fat: retain endothermic heat. High metabolism: 4-chambered heart, diaphragm: bones of jaws evolved into middle ear bones, most mammals have differentiated teeth. Really took off after the end-cretaceous extinction (65 my) There are three extant clades of mammals: monotremes: egg-laying mammals; no nipples, marsupials: mammals with a pouch, eutherians: placental mammals. Embryo develops within a placenta in the mother"s uterus: fetus is born very early in its development.

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