BIO 311C Textbook Notes based on Handout 4
BIO 311C Textbook Notes based on Handout 4 Bio 311C
Popular in Introductory Biology I
verified elite notetaker
Popular in Biology
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.
Reviews for BIO 311C Textbook Notes based on Handout 4
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
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. 4090C 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
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'