Download - Updated Nov 11, 2005 Created by C. Ippolito Dec. 9, 2001 Origin of Life Chapter 4 pages 67 -87
Updated Nov 11, 2005
Created by C. Ippolito
Dec. 9, 2001
Origin of Life
Chapter 4pages 67 -87
Updated Nov 11, 2005
Created by C. Ippolito
Dec. 9, 2001
Question?
Where does life come from?
The ancient Greeks first asked this question.
They devised two possible answers:
Updated Nov 11, 2005
Created by C. Ippolito
Dec. 9, 2001
AbiogenesisBelief that living things could arise
from nonliving materials.Also known as “spontaneous
generation”Many examples: Maggots are formed from old meat mice can form from dirty shirts, water,
and wheat hidden in a closet frogs come from mud
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Active Principle
Aristotle proposed that an active principle brought life to nonliving materials. Humans get it from parents Maggots get it from meat Frogs get it from mud
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Biogenesis
Belief that living things could only come from other living things.
Francisco Redi, a 17th century scientist tried to prove this
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Francisco Redi
Maggots from flies.
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Redi’s Hypothesis
Maggots on meat come from another living thing.
Redi noticed flies around decaying meat, so he proposed that maggots were related to the flies
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Redi’s Experiment
Meat in open jar.
Maggots appear in jar.
Meat and maggots gone.
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Conclusion of Time
Meat became maggots which left to find food.
To prove maggots were flies he repeated experiment by covering one jar after maggots appeared.
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Controlled Experiment
Control
Covered
Flies appeared
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Redi’s Conclusion
Maggots are immature flies that use meat as food.
He now proves that flies leave something on meat to form maggots.
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Another Experiment
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Biogenesis accepted
Redi’s work convinced scientists that biogenesis was true. Leeuwenhoek discovers “animalicules” in water with his simple microscope Abiogenesis was in vogue again
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Needham Vs. Spallanzani
Broth becomes microbes.
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Needham
Believed in abiogenesis:boiled broth to kill microbescorked flasks to stop life incork allowed air the “vital principle” in
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Needham Experiment
fresh broth
boiled broth
corked broth
its alive
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Spallanzani
Believed in biogenesis:didn’t boil long enough to killcork too porous; new life in
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Spallanzani Experiment
short boil
cork
its alive
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Spallanzani Experiment
short boil
melted
its alive
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Spallanzani Experiment
longboil
melted
not alive
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Conclusion
Some of Spallanzani’s flasks are still free of life. Abiogenesis believers said he did not let “vital principle” in spores enter with air
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Louis PasteurLate 1800’s abiogenesis disproved
allowing air in keeping spores out. “Swan Necked Flask” curves let air
through spores.
boiled no life
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Swan Necked Flask
Tilting fluid into neck proved spores were caught.
no life life
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Biogenesis true
Does all life have a common ancestor?
Where did very first life originate?
Three hypotheses were considered:
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Supernatural
All powerful God created life found in all cultures’ mythology no way to prove or disprove not scientific
creationism, scientific creationism, scientific creationism, intelligent creationism, intelligent designdesign
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Exobiological View
Life, like matter & energy always existed. It arrived from outer space as
spores Plausible but how did life start out
there.KISS Principle and Occam’s Razor
• If a simpler explanation possible go with it before you accept a more complicated explanation
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Chemosynthesis
Life developed on Earth by natural processes. Primitive Earth has all materials Primitive Earth has proper conditions. Most “scientific” explanation
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Oparin Haldane Hypothesis
Developed independently by two biochemists: JohnJohn HaldaneHaldane - England AlexanderAlexander OparinOparin - Russia
How life began after the BIGBIG BANGBANG.
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Known observations
Life composed of four (4) Major Classes of Complex Chemicals:proteinsproteinslipidslipids
carbohydratescarbohydratesnucleicnucleic acidsacids
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More observations Complex chemicals composed of simpler
BUILDINGBUILDING BLOCKSBLOCKS: proteinsproteins - amino acids lipidslipids - fatty acids & glycerol carbohydratescarbohydrates - sugars nucleicnucleic acidacid – nucleotides
Building blocks are composed of common elements: amino acids - C H O NC H O N fatty acids & glycerol - C H OC H O sugars - C H OC H O nucleotides - C H O N PC H O N P
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More observationsUniverse began with a gigantic
explosion that:made simple gasesgases condense and freezeplanets form
PrimitivePrimitive Earth atmosphereatmosphere different from today’s: ammoniaammonia - NH3methanemethane - CH4 waterwater vaporvapor - H2O
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More observationsAbundantAbundant energyenergy combines
gases:HeatHeat - from molten core & lavaSteamSteam - water contact with lavaElectricalElectrical - lightning in stormsRadiantRadiant - UV & IR radiation of sun
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Chemical Evolution EnergyEnergy from heat, light, electricity, and radioactivity
causecause new chemicalchemical bondsbonds to form; StableStable bonds remainremain; UnstableUnstable bonds breakbreak downdown; RandomRandom formation of bondsbonds in gases formform the chemical
buildingbuilding blocksblocks; Building blocks condense and rain into the oceans
forming a HotHot ThinThin SoupSoup; HotHot ThinThin SoupSoup - contains randomly formed sugarssugars, fattyfatty
acidsacids, glycerolglycerol, aminoamino acidsacids, and primitiveprimitive nucleotidesnucleotides; Heating and cooling with night and day more
condensation and bonding; Continued input of energyenergy randomlyrandomly formsforms macromoleculesmacromolecules from the building blocks;
The macromolecules condense into the oceans forming the HotHot ThickThick SoupSoup;
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Cellular Evolution HotHot ThickThick SoupSoup - contains proteinsproteins, lipidslipids, nucleicnucleic acidsacids, and
carbohydratescarbohydrates; Macromolecules aggregate to form cell-like clusters called
coacervatescoacervates or proteinoidsproteinoids; “precells” use macromolecules in oceans as food, forming the
first heterotrophsheterotrophs; They release free energy by fermentationfermentation forming carboncarbon
dioxidedioxide (CO2) in the atmosphere; CO2 in atmosphere slows random synthesis of molecules; Food in the oceans becomes scarce; Cell clusters develop pigments like chlorophyllchlorophyll, that captures
light Cell clusters - capture light - make food -photosynthesisphotosynthesis -
autotrophsautotrophs; Cell clusters add free oxygen (O2) to the atmosphere
Atmospheric O2 reduces mutating UV light penetration
Scarcity of free sugar and presence of O2 causes appearance of respiratory heterotrophsrespiratory heterotrophs.
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Experimental Evidence
Chapter 4pages 73-80
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Urey Miller Experimentlaboratory apparatus simulated
conditions for hot thin / hot thick soup.closed glass system, filled with waterammonia and methane gases were
pumped inwater heated, electrodes in gases gave
sparksultraviolet and infrared lampscondenser used to cool gasesruns for a week.
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Urey Miller Apparatus
water
heater
NH3
CH4
light
electrode sparks
condenser
coldwarm
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Conclusion
Scientists removed some fluid from the water and found: simple amino acids simple sugars
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Fox Experiment
Fox took material similar to those in Urey’s results altered the pH as proposed in “puddle” of soup coacervate aggregates were formed
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Woese Hypothesis
Proposed that “pre-cells” formed as droplets on dust entering the atmosphere
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Cairns-Smith Hypothesis
One problem not solved is reproduction
Cairns-Smith proposes that naked crystals of clay can replicate and were the first to store information