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79 Cards in this Set
- Front
- Back
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Why can't CO2 be the greenhouse gas that warmed the earth because of the Faint Young Sun Paradox?
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It ca't be from CO2 because a high enough amount of CO2 to lower solar radiation would have resulted in precipitation of the mineral siderite (FeCO3) in soils.
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What is the alternative greenhouse gas that could have warmed the earth during the faint sun paradox?
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Methane - but that's only possible in an atmosphere without oxygen. As little as .1% methane in the atmosphere would be enough to keep the earth warm.
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How do we know there was little oxygen in the atmosphere prior to 2.4 Ga?
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Redox-sensitive minerals (pyrite and uraninite) occur as detrital grains in surface rocks. This couldn't happen if there was free oxygen
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What is the explanation for how Methane is consumed and produced by organisms?
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Life (breathable atmosphere) becomes part of the climate feedback
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What and where and when was the first indirect chemical evidence of life?
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There is a light carbon isotope composition of graphite specks in metamorphosed sedimentary rocks in Isua, Greenland at 3.779 Ga.
The graphite specs suggest that they are metamorphosed remains of organic matter |
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What, where, and when was the first trace fossil?
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A biogenic sedimentary structure produced by a community of micro-orgasims (a trace fossil) in the Strelley Pool stromatolites, Australia at 3.45 Ga.
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What, where, and when is the first microbe fossil? What is the evidence supporting it?
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The Strelly pool microbe fossile in Austrilia around 3.4 Ga.
1) Right Size 2) Cell walls consisten with biological origin 3) postmortem breakdown consistent with modern microbial decay (not mineral) 4) form chains and clusters 5) carbon isotopes are light (i.e consistent with biological origin), 6) Interpreted to have sulfur based metabolism |
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What is the next youngest claim that is well established of microfossils? Where?
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The Swartkoppie microfossils in south africa around 3.26 Ga.
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Comparing the earliest indications of life, when comparing the find in Isua and South Africa what is concluded?
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If the Isua interpretation is correct, then life appeared early. However if the Swartkoppie is loser to first life, then life is more difficult and took several 100 million years to appear.
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What is life defined as?
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Life is growth, metabolism, and reproduction
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What is the simplest life in present day?
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prokaryotic cell
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What is cell theory?
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All living matter is composed of cells
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What three domains include life?
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Archaea, bacteria, eucaryota
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What are the molecules that make up cells?
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(Polymers - monomers)
Proteins - strings of amino acids Nucleic Acids (RNA and DNA) - strings of nucleotides Lipds - have a hydrophilic end and a hydrophobic end Polysaccharids - strings of sugar molecules Abiotic amino acids - Miller- Urey experiment and subsequent similar experiemnts produce amino acids from simple mixture of inorganic compounds (amino acids) and electrical spark; Prebiotic or Primordial soup |
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What is the central dogma of molecular biology?
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DNA is transcribed to RNA which is translated to protein; DNA is replicated
Central Dogma is too complex to aris spontaneously, but RNA can act as both an enzyme and an information recorder ( ie the jobs of proteins and DNA respectively) RNA polymers can be catalyzed by the caly minerals |
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How does metabolism work?
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Metabolism uses energy to build organic matter or breaks down organic matter to extract energy
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The metabolic pathway of all living things start from what?
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Citric Acid Cycle ( = Krebs Cycle = Tricarboxylic Acid Cycle)
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What is the citric Acid Cycle?
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In modern cells, this process takes a small organic molecule (pyruvate derived from glucose) and breaks it into H2) CO2 and releases energy in the form of ATP; each of the components of the cycle is replaced as the system runs through each step
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What is a Heterotroph?
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Breaks down organic matter for energy
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What is an Autotroph?
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uses energy from environment to make organic matter
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What can the Reverse Citric Acid cycle do?
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It can be used to MAKE organic carbon from CO2, H2, and environmental energy i.e - autotrophic process
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The fact that the Citric Acid cycle occurs in all living things suggest what?
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That is was present very early in life. Its simple molecular parts can all be found abiotically
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If the citric acid cycle occurs in reverse what could it provide?
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a means of making organic matter
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Where is the reverse citric acid cycle found?
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Aquificales, a branch near the base of the bacterial domian - exactly where predicted if that was the ancestral state
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What is needed for assembling an organism from non-living components?
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1) An energy source - reduced mineral compounds (an electron source)
2) a metabolic cycle in which the compound at each step is recoverd as the cycle runs - the reverse Citric Acid cycle 3) a boundary - a spontaneously formed lipid bilayer 4) connecting energy and information (i.e metabolism and genes) - adenine is an RNA base and also the backbone of ATP, the cell's energy molecule; affecting one system with affect the other 5) grow and reproduce - lipid bilayers divide when they grow By putting linked metabolism and information systems in a growing lipid bilayer these components from a reproducing system |
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What is a system?
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a regularly interacting or interdependent group of items forming a unified whole
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What is emergent properties?
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Aspects of the system that arise through the interactions of the component parts, but are not properties of the components themselves
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What is lineage?
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a string of ancestors and descendants in which descendants inherit properties of their ancestors
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What is evolution?
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descent with heritable modification in a lineage
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What is selection?
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a prolific ancestors pass the properties that make them prolific to their descendants; these use limited resources at the expense of lineages that are less prolific
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What are the two parts of the evolution algorithm?
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1) heritable variation is generated
2) then it is culled by selection. The non-random survivors provide the source for heritable variation in the next generation |
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How do organisms proliferate?
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by being better at converting resources into more to themselves OR by finding unexploited resources, thereby dodging competition (until the new resource becomes limiting)
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What is the source of variation in prokaryotic lineages?
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copying errors; only works because the numbers of prokaryotes are so large
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What drives metabolism?
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Redox reactions (chemical reactions in which one compounds loses an electron and another gains an equivalent electron)
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What is reduction?
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gain of electrons
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What is oxidation?
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loss of electrons
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What is organic matter?
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reduced carbon
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What happens to organic matter when it is oxidized?
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it releases energy
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What are prokaryotes maters of?
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using different materials to oxidize fuels.
Methanogens can use H2 and CO2 to produce CH4 Sulfate-reducing bacteria oxidize organic matter using SO4 rather than O2 and releases H2S rather than H2O? |
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What is chemolithoautotroph?
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an organism that uses a mineral substrate to synthesize organic matter
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What is photoautotroph?
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an organism that uses light to synthesize organic matter
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How does Oxygenic Photosynthesis work?
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CO2 + H2O + sunlight => CH2O + O2
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What are the critical parts of light reactions?
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water splitting complex, reaction center II and reaction center I
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What are dark reaction?
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They take electrons and H+ ions from light reactions to synthesize sugar
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What is chlorophyll?
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light catching pigment; a porphyrin ring with Mg++ ion at its center
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What is water splitting complex?
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breaks H2O into H+, electrons, and O2 (O2 is a waste product)
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What are the three lateral or horizontal gene transfers?
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1) transformation
2) transduction 3) conjugation |
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What do lateral gene transfer have?
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They have distributed reactions centers throughout the bacterial domain of life
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How can RCI and RCII be inherited?
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Occurrence of both RCI and RCII could be inherited from ancestor or combined via lateral gene transfer
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Where does oxygenic photosynthesis get it's electron?
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It gets an electron by breaking H2O, but the electron produced is so low-energy it takes two steps to excite it enough to make organic carbon
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RCI and RCII cannot operate together? why?
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The interfer with one another, unless they have a source of electrons to replace the ones lost in the electron transfer chain
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Where does RCI occur?
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RCI occurs in green bacteria based on H2S rather than H2O (as in oxygenic photosynthesis)
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Where does RCII occur?
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in purple bacteria as a way to generate electrons
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What does phylogeny of phototrophic bacteria indicated?
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that reaction centers (i.e. chlorophyll) only evolved once; it also probably wasn't originally autotrophic (ie, it generated ATP, but organisms couldn't make organic matter from inorganic matter)
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What are Banded Iron formations?
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oxidized Fe, but do not necessarily require O2 to be oxidized ( prokaryotes are known to oxidize FE without; cease to be part of the rock record ~ 1.8-1.7 Ga)
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What are stromatolites?
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biogenic sedimentary structures produces by phototrophs, but not necessarily oxygenic phototrophs; exception = tumbiana Fm. (2.724 Ga), which has stromatolites without any other oxidant than H2O
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What are Microbial body Fossils?
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Generally not diagnostic of type of prokaryote; exception = Nauga FM (2.59 - 2.55 Ga), which preserves mucilage sheaths characteristic of cyanobacteria
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What are biomarkers?
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fossil molecules that characterize particular bacterial groups
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What are the earliest cyanobacterial biomarks?
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Maddina fm. (~2.7 Ga), but these are not from the photosynthetic part of the cyanobacterial metabolic machinery
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What are carbon isotopes?
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organic matter that has a lighter carbon isotope signature than that in inorganic carbon from which it was created
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When and why was there a sharp increase in lighter organic carbon isotopes?
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around 2.7 Ga, it indicated that there was a sudden change in the way organic matter was cycled.
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What is the Mass independent Fractionation of Sulfur Isotopes?
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MIF of sulfur is characteristic of very few chemical reactions; one of these is driven by ultraviolet radiation.
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When do rocks stop showing MIF?
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Rocks older than 2.45 Ga do, rocks under than 2.45 Ga don't
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What does that the lack of MIF after 2.45 Ga indicate?
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That u/v radiation was much less intense. U/V radiation is blocked in Earth's atmosphere by ozone (O3), which requires O2 to form. In other words, MIF is shut down when Ozone (i.e oxygen) builds up in the atmosphere
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What are redox sensitive minerals?
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pyrite, uraninite, and siderite react with oxygen;
before ~2.3 Ga, they are found as detrital grains, but not in younger rocks. |
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When did oxygenic photosynthesis appear?
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oxygenic photosynthesis (cyanobacteria) appeared by 2.8-2.7 Ga.
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When did oxygen substantially rise in atmosphere?
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~2.4-2.3 Ga
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What happened with the rise of the oxygen?
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The rise of oxygen resulted in reaction with methane in atmosphere; without methane's greenhouse effect, global temperature dropped.
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What are the evidence for snowball earth?
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Glacial diamictite, dropstones, and striations at many locations around the world (e.g. the Huronian Glaciation in Canada and the Makganyene Glaciation in South Africa), many of which were at low latitudes at the time
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What did the red beds of the snowball earth indicate?
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Glacial deposits overlie reduced minerals and are overlain by red beds, indiciateing that the Snowball coincided with the Rise of O2
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What do the recent findings suggest about sulfur in the canfield ocean?
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That sulfur was only elevated at intermediate depths, allowing Fe to remain dissolved in the deep ocean
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What is the thermohaline circulation? what does it do?
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It is the great ocean conveyor, it is how surface waters get into the deep ocean. In the present, this is how oxygen gets into the ocean; during the proterozoic, when o2 were lower, it was all consumed by respiration of sinking organic matter
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What is the oxygen minimum zone?
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a layer of ocean water ~ 1km deep where respiration of sinking organic carbon consumes all available oxygen; in the proterozic this is where sulfate respiration would have produced reduced sulfur, preventing deissolved Fe from reaching shallow waters
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What is Nuna?
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a supercontinent from 1.8-1.3 Ga
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What is Rodinia?
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a supercontinent from 1.2 - 0.7 Ga
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What happens during the assembly of supercontinents?
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collisional mountain belts expose fresh rock to weathering in the atmosphere, altering the climate
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What happens during the break up of supercontinents?
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During the break up, numerous hot, young mid oceanic rifts displace water from the oceans basins, causing rising sea levels
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Whats the reason call upon sulfur to remove Fe rather than O2 in the canfield ocean?
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that the deep oceanic sediments were in anoxic waters
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What resulted in the end of BIF deposition around 1.8-1.7 Ga?
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O2 in the atmosphere oxygenated surface waters and released sulfur from weathering rocks on land; that sulfur was delivered to the ocean, where it reacted with dissolved Fe, this resulted in the end of the BIF deposition around 1.8-1.7 Ga
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