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



Dec. 9, 2001

Question?

Where does life come from?

The ancient Greeks first asked this question.

They devised two possible answers:



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



Dec. 9, 2001

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



Dec. 9, 2001

Biogenesis

Belief that living things could only come from other living things.

Francisco Redi, a 17th century scientist tried to prove this



Dec. 9, 2001

Francisco Redi

Maggots from flies.



Dec. 9, 2001

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



Dec. 9, 2001

Redi’s Experiment

Meat in open jar.

Maggots appear in jar.

Meat and maggots gone.



Dec. 9, 2001

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.



Dec. 9, 2001

Controlled Experiment

Control

Covered

Flies appeared



Dec. 9, 2001

Redi’s Conclusion

Maggots are immature flies that use meat as food.

He now proves that flies leave something on meat to form maggots.



Dec. 9, 2001

Another Experiment



Dec. 9, 2001

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



Dec. 9, 2001

Needham Vs. Spallanzani

Broth becomes microbes.



Dec. 9, 2001

Needham

Believed in abiogenesis:boiled broth to kill microbescorked flasks to stop life incork allowed air the “vital principle” in



Dec. 9, 2001

Needham Experiment

fresh broth

boiled broth

corked broth

its alive



Dec. 9, 2001

Spallanzani

Believed in biogenesis:didn’t boil long enough to killcork too porous; new life in



Dec. 9, 2001

Spallanzani Experiment

short boil

cork

its alive



Dec. 9, 2001


short boil

melted

its alive



Dec. 9, 2001


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



Dec. 9, 2001

Louis PasteurLate 1800’s abiogenesis disproved

allowing air in keeping spores out. “Swan Necked Flask” curves let air

through spores.

boiled no life



Dec. 9, 2001

Swan Necked Flask

Tilting fluid into neck proved spores were caught.

no life life



Dec. 9, 2001

Biogenesis true

Does all life have a common ancestor?

Where did very first life originate?

Three hypotheses were considered:



Dec. 9, 2001

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



Dec. 9, 2001

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



Dec. 9, 2001

Chemosynthesis

Life developed on Earth by natural processes. Primitive Earth has all materials Primitive Earth has proper conditions. Most “scientific” explanation



Dec. 9, 2001

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



Dec. 9, 2001

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



Dec. 9, 2001

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;



Dec. 9, 2001

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.



Dec. 9, 2001

Experimental Evidence

Chapter 4pages 73-80



Dec. 9, 2001

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.



Dec. 9, 2001

Urey Miller Apparatus

water

heater

NH3

CH4

light

electrode sparks

condenser

coldwarm



Dec. 9, 2001

Conclusion

Scientists removed some fluid from the water and found: simple amino acids simple sugars



Dec. 9, 2001

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



Dec. 9, 2001

Woese Hypothesis

Proposed that “pre-cells” formed as droplets on dust entering the atmosphere



Dec. 9, 2001

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

Updated Nov 11, 2005 Created by C. Ippolito Dec. 9, 2001 Origin of Life Chapter 4 pages 67 -87.

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Transcript of Updated Nov 11, 2005 Created by C. Ippolito Dec. 9, 2001 Origin of Life Chapter 4 pages 67 -87.