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Unformatted text preview: Lecture 18- Origins of Life Timeline Earth formed 4.6 billion years ago Origin of life- 4 billion years ago First prokaryotes- 3,800 million years ago Oxygen in atmosphere- 2,700 million years ago First eukaryotes- 2,200 million years ago First multicellular eukaryotes- 1,400 million years ago Animals- 600 million years ago Land plants- 500 million years ago Humans- 150,000 years ago *In the relative span of one year, humans evolved 11:49pm, December 31; VERY late *Life started very quickly after the formation of Earth What do you need to make life? - Abiotic synthesis: make molecules important to life: amino acids, proteins, sugars- Heritable information, the ability to transfer information onto daughter cells, next generation- Formation of cells; separation of molecules from the external environment Geophysical Stage- Early atmosphere: , , , , H2O NH3 H2 CH4 H2 S- All the atoms important for building molecules were there- Lots of high energy, UV light, lightening- Reducing atmosphere (no O2 )-Oxygen is very electronegative, rips electrons off things, thus you cant build molecules with oxygen there. Since -Oxygen is very electronegative, rips electrons off things, thus you cant build molecules with oxygen there....
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- Spring '09