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BIO 311C Textbook Notes based on Handout 4

by: Sena Sarikaya

BIO 311C Textbook Notes based on Handout 4 Bio 311C

Marketplace > University of Texas at Austin > Biology > Bio 311C > BIO 311C Textbook Notes based on Handout 4
Sena Sarikaya

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About this Document

These are notes covering concepts from select sections of Campbell Biology Edition 10 chapter 25. The concept check questions and photo content are not my own. The concept check questions and photo...
Introductory Biology I
Dr. Buskirk
Class Notes
Biology, intro to biology, textbook notes, textbook, Chmical evolution, oxygen revolution, Early abiotic earth, origins of eukaryotes
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This 5 page Class Notes was uploaded by Sena Sarikaya on Wednesday September 21, 2016. The Class Notes belongs to Bio 311C at University of Texas at Austin taught by Dr. Buskirk in Fall 2016. Since its upload, it has received 6 views. For similar materials see Introductory Biology I in Biology at University of Texas at Austin.


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Date Created: 09/21/16
Textbook Notes from Handout 4 Ch. 25 25.1 Conditions on Early Life made the Origin of Life Possible  ­how did living cells appear? ­observations & experiments propose one scenario  ­chem. & physical processes could have produced simple cells through 4 stages 1. abiotic synthesis of organ. molecules 2. synthesis of small organ. mol. to macromolecules 3. packaging of molecules in protocells ­protocells: droplets w/ membranes & internal chem. diff. from  surrounding 4. origin of self­replication molecules ­> inheritance A. Synthesis of Organic Compounds on Early Earth ­no water but lots of water vapor ­hot ­little oxygen ­compounds released by volcanic eruptions ­as earth cooled ­> water vapor condensed to bodies of water & H into space ­A.I. Oparin & J.B.S. Haladane ­independently hypothesized early earth atmosphere = reducing environ ­organ compounds form from simpler mol. ­lightning & UV radiation = nrg for synthesis ­Stanley Miller & Harold Urey ­lab conditions like early earth ­yielded amino acids & organ. comp. ­another hypothesis that organ. comp. produced in deep­sea hydrothermal vents ­hydrothermal vents: areas on sea­floor w/ heated water & minerals that  come from earth’s interior into the ocean ­some “black smokers” release hot water that make comp. unstable ­alkaline vents: release high pH warm water (more suitable for  origin of life)  ­pH 9­11 ­temp. 40­90C ­another source for organic mol. = meteorites ­ex. Murchison meteorite contains amino acids ­not from earth b/c contains D & L isomers ­organism only make & use L isomers B. Abiotic Synthesis of Macromolecules ­abiotic synthesis of RNA can occur spont. from precursor mol.  ­amino acid or RNA drips on hot sand, clay, rock produces polymers ­spontaneous ­no enzymes or ribosomes  C. Protocells ­all organisms must reproduce & process nrg (metabolism) ­necessary conditions may be met in vesicles ­ex. vesicles form spontaneously w/ lipids in water ­adding montmorillonite (soft mineral from volcanic ash) incr. rate of  vesicle self­assembly ­surface for organ. mol. conc. ­inc. likelihood of mol. rxns & forming vesicles ­abiotically produces vesicles can “reproduce” on their own & grow/ inc. size w/o diluting contents ­vesicles can absorb montmorillonite particles  ­RNA & organ. mol. attached ­some vesicles have selectively permeable bilayer & do metabolic rxns w/  external reagents D. Self­Replicating DNA ­first RNA not DNA ­ribozymes: RNA catalysts ­make short RNA complementary copies w/ supplied nucleotides ­RNA mol. w/ certain nuc. seq. replicates faster & w/ fewer errors than other seq.  ­RNA = template for DNA ­DNA more chem. stable for genetic info & replicated more accurately 25.3 Key Events in Life’s History Include the Origins of Unicellular & Multicellular Organisms  & The Colonization of Land ­geologic record: standard time scale diving earth’s history into 4 eons ­1  eon = Hadean ­2  eon = Archaean ­3  eon = Proterozoic th ­4  eon = Phanerozoic ­Paleozoic ­Mesozoic ­Cenozoic A. The First Single­Celled Organisms ­stromatolites: layered rocks that form when certain prokaryotes bind sediments ­earlies direct evidence of life (3.5 billion y.a.) ­currently found in few shallow marine bays a. Photosynthesis and the Oxygen Revolution ­most atmospheric oxygen = water splitting from photosynthesis ­at first w/ photosynthesis the free oxygen dissolved in surrounding water ­@ high enough conc.  it would react w/ elements dissolved in  water  ­ex. iron ­> iron oxide ­> sediments ­once all dissolved iron precipitates, more oxygen dissolves ­oceans etc. saturated w/ oxygen now ­then oxygen “gasses out” from water to atmosphere ­cyanobacteria = oxygen­releasing photosynthetic bact  ­originates 2.7 billion y.a. ­ oxygen had huge impact on life ­attacks chem. bonds ­inhibits enzymes ­damages cells ­doomed prokaryotes ­some survived in anaerobic conditions ­some adapt w/ cellular resp. b. The First Eukaryotes ­endosymbiont theory: mitochondria & plastids (things like chloroplasts)  were small prokaryotes that started living w/ larger cells ­developed mutually beneficial relationship ­serial endosymbiosis: mitochondria evolved before plastids b/c of  endosymbiotic events ­all eukaryotes of mitochondria like remains  ­not all have plastids ­evidence for endosymbiotic origin of mitochondria & chloroplast… ­inner membranes have transport systems like prokaryotes ­replicate by splitting process like prokaryotes ­circular DNA like bacteria; no large histones ­cellular machinery like ribosomes ­ribosomes more like prokaryotes than eukaryotes B. Origin of Multicellularity a. Early Multicellular Eukaryotes ­oldest fossils of mut. euk. from 1.2 billion y.a. ­from microbial world to evolutionary change b. The Cambrian Explosion ­Cambrian explosion: present day animal phyla suddenly appearing C. Colonization of Land ­milestone in history of life End of Chapter 25 Qs 1. Fossilized stromatolites A. formed around deep­sea vents B. resemble structures formed by bacterial communities that are found  today in some shallow marine bays C. provide evidence that plants moved onto land in the company of fungi  around 500 million years D. contain the first undisputed fossils of eukaryotes and date from 1.8  billion years ago 2. The oxygen revolution changed Earth’s environment dramatically. Which of  the following took advantage of the presence of free oxygen in the oceans and  atmosphere? A. the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules B. the persistence of some animal groups in anaerobic habitats C. the evolution of photosynthetic pigments that protected early algae  from the corrosive effects of oxygen D. the evolution of chloroplasts after early protists incorporated  photosynthetic cyanobacteria 1. Which of the following steps has not yet been accomplished by scientists  studying the origin of life? A. Synthesis of small RNA polymers by ribozymes B. Formation of molecular aggregates with selectively permeable  membranes C. Formation of protocells that use DNA to direct the polymerization of  amino acids D. Abiotic synthesis of organic molecules


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