GEO 102Exam # 3 Study Guide Lectures: 22- 30Lecture 22 (October 22)Time Scale to Memorize- Eons: Hadean, Archaen, Proterozoic, Phanerozoic - Eras of the Phanerozoic: Paleozoic, Mesozoic, Cenozoic- Periods of the Paleozoic and Mesozoic: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, and CretaceousOrigin of the Universe- 13.75 billion years (give or take 0.11)o Initially inferred from expansion- Doppler shifo Radiation remains-cosmic background radiationo First true atoms formed ~379,000 years afer Big BangOrigin of the Sun and Earth- Matter from prior stars condensed (gravity)- Planets accreted from rotating disk of matter- Less volatile matter near sun (stony planets), less dense accreted farther (gaseous planets)- Moon formed from early impactThe Atmosphere- Originated through outgassing- 1st one (mostly H) was lost to solar wind- Core differentiation/ magnetism protect 2ndLecture 23 (October 24) Core Differentiation- Early Earth was homogenized- Over time (as short as 30 million years) dense matter (Ni and Fe) sank to form core- Acted as an electro magnet and protected 2nd atmosphere from solar windo 1st atmosphere is lostWater- Came from comets but Earth used to be so hot that it could not exist in liquid form- First all vapor- Light could not penetrate- Cooled to condensation point- Rain filled basinsOxygen- Came much later. Mostly from photosynthesis and chemosynthesis- First oxygen from photochemical dissociationo Very small amount- ~2% of today- Larger quantities came from photosynthesiso Seen in BIF’s o Red bedso Initially from Prokaryotes Prokaryotes- life before seeds. Single cell organisms without a nucleusTectonics, Weathering, Atmosphere, and Climate- Extensive continents by 3.6 Ga- Initial uplif led to weathering- Beginning of CO2 cycleo Weathering:o CaSiO3+CO2-----CaCO3+SiO2o Melting of marine critters at subductionso CaCO3+SiO2----CaSiO3+CO2CO2-Weathering Thermostat- Feedback is critical- Increased tectonic activity leads to new land and uplif- This leads to increased weathering- Increased weathering traps CO2 in resultant sedimentary rocks- Rocks are subducted and cycle resumesFeedback- Hot periods increase rains and water vapor (heating the Earth more)- Rains increase weathering- Ne sedimentary rocks trap CO2- Cools the Earth and lessens precipitation and weathering- Sedimentary rocks subducted and it cyclesLecture 24 (October 27)What is Life?- How do we know something is alive?o How is a rock different from a tree?o Reproductiono Metabolism- a sequence of chemical reactions- What is a Virus?o Not aliveo It has DNAo It reproduceso But it can’t reproduce by itself It has to hijack a cell in some other bodyo It doesn’t metabolize by itself eithero Outside another body it simply existso Viruses evolveBetween life and not-life- Viruses are in a grey area- They DO NOT represent the first proto-life- Microspheres might better resemble the first lifeo They are organic (carbon based) but arise by themselveso They grow and divide like cells- but more randomlyWhat are living things made of?- Amino acids- life’s building blocks o You may have heard of them from your foodo Can originate from non-living things- How did they originally form?o Miller-Urey experimento Chemosynthesiso Geobiology Did life come from rocks or clay or undersea volcanoes? Many think soHow do they make amino acids?- You need:o Carbon, nitrogen, hydrogen, and oxygeno These are in the early atmosphere CO2, H2O,N2, CH4, and NH4o An external energy source is needed to start the reactiono Lightningo Chemical energyExperiments- Miller-Urey showed it could be done, but used the wrong atmosphere- More recent work has done this in a wide variety of circumstances- Several possible “cradles” of early life have been identified- This is but the first step thoughProteins- Amino acids are part of proteins- Our bodies synthesize proteins- How did they begin?o Simple “proteinoids” have been formed in the labo Experiments suggest that it may not have happened in water afer all - Group of protenoids cluster and form cell-like structures protected by membranesIs this how it happened?- There is still a lot to be learned and it is developing story –RNA and DNAo Reproductiono Space?- The geological record’s earliest evidence of life is in indirecto Stable carbon isotopes at 3.8 bya- The first undisputed fossils show up about ~3.5 byao Prokaryotico Anoxic- can not live without oxygenWhat did these organisms eat?- The earliest life is derived energy from breaking down components in their environmento Would not have lasted long- Later life would ferment materialso Molecules such as sugars are split releasing carbon dioxide, alcohol, and energy- About 3.5 bya photosynthesis began to be widespreadTake home tip: how oxygen became popular. One way didn’t require life- Phot and chemosynthesis. Life is from building blocks that can self-assemble. Still looking for how to tell ifthings are life- life in extreme environments and making synthetic lifeLecture 25 (October 29)Introduction to free oxygen- two processes introduced free oxygen into the atmosphereo Hadean/ Archean1. Photochemical dissociation- involves ultraviolet radiation in the upper atmospherea. The radiation disrupts water molecules and releases their oxygen and hydrogenb. This could account for 2% of present-day oxygenc. But with 2% oxygen, ozone forms, creating a barrier against ultraviolet radiation2. More important were the activities of organisms that practiced photosynthesisLife and atmosphere- The first process – making ozone- helped to make later lifeo UV light destroys key building blocks of life- The second process could only occur because of lifeo Irony is that oxygen is deadly to the organisms that produced the oxygenWhat were these organisms?- Single cell (true bacteria)- Not many organelles (simple cells)- Photosynthetic and chemosynthetic - That produced oxygen as a metabolic productFirst fossils- Photomicrographs from western Australia’s 3.3-to 3.5 billion year old warrawoona groupStromatolites- Present-day stromatolites grow as sediment is trapped on sticky mats of blue-green algae (cyanobacteria) o Now restricted to environments where snails cannot live- The oldest know undisputed stromatolites are found in rocks in South Africao 3.0 billion years old o Probable ones from the Warrowoona Group in Australiao 3.3 to 3.5 billion years oldLecture 26 (November 3)- Why do geologists