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Last LectureOutlineLectureEES 1040 1st Edition Lecture 7Last LectureEvolutionOutlineI. “Precambrian”II. CalendarIII. Precambrian 542 M – 4.6 BA IV. Archaean LifeV. PhotosynthesisVI. How does this help?VII. Nothing older, but hardly any rocks olderVIII. Life on Earth gets started very, very earlyLectureI. “Precambrian”A. Earth formed ~4.6 BAB. Fossil record of common fossils ~542 MAC. Pharozoic only ~ 12% of Earth HistoryII. CalendarA. “Precambrian” 1. January 01  Mid-NovemberB. Paleozoic ~1 month1. Nov 19 Dec 13C. Mesozoic ~2 weeks1. December 13  Dec 27D. Cenozoic ~5 daysThese 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.1. Dec 27 –Dec 31E. Humans1. ~7 hoursIII. Precambrian 542 M – 4.6 BA A. 542 MA (start of Cambrian)B. Proterozoic Eon1. Neoproterozoic2. 1000 MA3. Mesoproterozoic4. 1600MA5. PaleoproterozoicC. 2500 MAD. Archaean EonE. 3960 MAF. Hadean Eon (No record)G. 4.6 BAIV. Archaean LifeA. First definite fossils1. ~3.5 BAB. Cyanobacteria (Kingdom Eubacteria)1. Photosynthetic bacteria with chlorophyll-A2. Form filaments (threads) of individual cells3. Cherta. Formed through hardening of fine silica gelb. Can preserve shape of individual cells4. 1950s South Africaa. Onverwacht Group5. Western Australiaa. Warrawoona Group6. Filamentous fossils discovered in fine chert7. Interpreted as ancient cyanobacteria C. On substrate 1. Evolve to form bacterial matts2. Sunlight3. Added sediment4. Trapped in filaments5. Very distinctive layering and banding of sedimenta. Stramatolites D. 3.2 BA South Africa1. Fig Tree Group2. Oldest known stomatolites V. PhotosynthesisA. Sun light (form of energy)B. Plants (Chlorophyll)1. Green substance2. Catalyst for photosynthesisC. Chlorophyll photosynthesis1. CO2 + H2O  CH2O + O2a. Carbon dioxide + water  sugar + oxygenD. Respiration1. Burns sugar and oxygen  carbon dioxide and water2. Energy used for organisms metabolismE. But plant also needs sugars to grow1. To make new cells and tissuesF. When plants uses sugars for this purposes, doesn’t burn O2, releases it to atmosphereG. Overall, plants use up CO2 and make O21. “lungs of the planet”VI. How does this help?A. There are 2 stable isotopes of carbon © in atmosphere1.12C and 13C2. We know how common each isB. When an organism photosynthesizes, it preferentially uses the lighter 12C isotopeC. When one finds elevated 12C/13C ratios in carbon trapped in ancient sediments, 1. Strong evidence of photosynthesis and lifeD. Isua Formation1. Southern Greenland2. “banded iron” iron mineral chert3. Elevated 12C/13C ratioa. 3.8 BA VII. Nothing older, but hardly any rocks olderA. as far back as possible to look, there was lifeB. as soon as the planet was ready, life existedVIII. Life on Earth gets started very, very earlyA. As soon as conditions were right, life evolved1. And probably happened in other


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