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Lecture 5

Lecture 5 Early Life.docx

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Life Sciences
Luc Bernier

Early Life: Geological Scale:  Hadean - time from the formation of the solar system and early accretion of the planet  The origin of life  Archaean - time of the beginning of life approx. 4-6 billion years ago  Follow by Proterozoic  Phanerozoic since then The Prebiotic Hadean Environment:  From creation of solar system: 4.6 Gyr billion years solar system once appeared to be like dust surrounding the sun the amount of current and past carbon/elements was determined millions of years ago  Earth received finite amounts of water vapour and carbon  Carbon dioxide on Earth: tied up in carbonate rocks, withhold carbon dioxide in solid form  Ex. limestone  Water: liquid mainly found in oceans, in other planets very different, carbon dioxide is mostly in Venus' atmosphere so it has a much more powerful green house affect, much hotter so no water found in Venus but it can be found in vapour on Mars, most water is frozen in permafrost Early Earth:  Earth was thought to be hell like; many volcanic eruptions and toxic "soups" Earth's Early Atmosphere:  Nitrogen was probably the same amount in Earth's atmosphere then and now but Oxygen was in much less supply then; with the lack of oxygen present many other gases seen instead like ammonia, etc  Some think that the carbon dioxide was held up in the Earth's crust  Early atmosphere was hard to control  Toxic soup on the early Earth The Miller-Urey Experiment:  Based on Oparin-Haldane hypothesis: life would have arisen from chemical reaction in earths atmosphere, leading to the formation of simple organic compounds  Current conducted, simple organic compounds were produced  Unanswered: is this an accurate representation  The diagram shows that the discharges from the Earth along with the other gases came from carbon dioxide and life The RNA World:  Earliest forms of life were based entirely on RNA o Ex. possibly viruses  Capable of self replication and enzymatic activity o Forms of RNA found in the last 30 years The Faint Young Sun:  4.4 to 4.0 Gyr: early sun was fainter by quarter to a third than it is now  How life moderates carbon dioxide in atoms during early stages of the Earth  What Earth would have looked li
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