orign of life

8/7/2019 orign of life

http://slidepdf.com/reader/full/orign-of-life 1/32

Origin of LifeOrigin of Life

Dr.K. Raghothama RaoDr.K. Raghothama Rao



Origin Of LifeOrigin Of Life Earth formed 4.6 billion years agoEarth formed 4.6 billion years ago

When, and how did life originate?When, and how did life originate?

Life is believed to have begun 3.5 billionLife is believed to have begun 3.5 billion

years agoyears ago

What was the primitive environment of What was the primitive environment of Earth like?Earth like?

Reducing, electron adding, atmosphereReducing, electron adding, atmosphere

No electron hogging oxygen gas wasNo electron hogging oxygen gas waspresent.present.



What is life?What is life?

DefinitionDefinitionA chemical system that A chemical system that

undergoes Darwinianundergoes Darwinian

evolution and degradesevolution and degrades

highhigh--quality energy fromquality energy from

its environment inits environment in

metabolismmetabolism

Common AssumptionsCommon Assumptions

Requires:Requires:

Free energyFree energy

Organic moleculesOrganic molecules

Liquid water (maybe!?)Liquid water (maybe!?)



Resolving the Biogenesis ParadoxResolving the Biogenesis Paradox

Spontaneous GenerationSpontaneous Generation

The idea that life can emerge from inanimateThe idea that life can emerge from inanimate

objectsobjects

Mice came from hayMice came from hay

Maggots came from rotting meat Maggots came from rotting meat

18621862--Louis Pasteur disproved spontaneousLouis Pasteur disproved spontaneousgenerationgeneration



Step One: Chemical EvolutionStep One: Chemical Evolution 1920s1920s--Oparin and Haldane:Oparin and Haldane:

Reducing atmosphere + high energy levelsReducing atmosphere + high energy levels

contributed to spontaneous chemical evolutioncontributed to spontaneous chemical evolution This cannot happen today do to the high levels of This cannot happen today do to the high levels of

oxygen in the atmosphereoxygen in the atmosphere

Sidney Fox:Sidney Fox:

Spontaneous polymerization occurs on hot sand orSpontaneous polymerization occurs on hot sand orclayclay

Produced protenoidsProduced protenoids



MillerMiller--Urey Experiment Urey Experiment

19531953

Tested the Oparin hypothesisTested the Oparin hypothesis Atmosphere was composed of water,Atmosphere was composed of water,hydrogen, methane, and ammoniahydrogen, methane, and ammonia

The experiment generated amino acidsThe experiment generated amino acidsand nucleic acids, as well as otherand nucleic acids, as well as otherorganic materialsorganic materials



After only one week

of continuous cycling«

-Amino acids

- other substances

found in livingorganisms

(i.e. urea)

Origin of basic

biological

molecules



Origin of basic

biological molecules



ProtobiontsProtobionts

Maintain different internal environment Maintain different internal environment

MicrospheresMicrospheres selectively permeableselectively permeable

protein membraneprotein membrane Displays osmotic swellingDisplays osmotic swelling

Stores energyStores energy

Has a membrane potentialHas a membrane potential

LiposomesLiposomes lipid bilayer:lipid bilayer: Grow and appear to split give birthGrow and appear to split give birth



CoacervatesCoacervates polypeptides, nucleic acids,polypeptides, nucleic acids,and polysaccharides:and polysaccharides:

Hydrophobic macromolecules surrounded byHydrophobic macromolecules surrounded byshell of water moleculesshell of water molecules

Can absorb substratesCan absorb substrates

Release productsRelease products

May have enzymes associated with themMay have enzymes associated with them

In chemical evolution the environment In chemical evolution the environment selects for best suited molecules to surviveselects for best suited molecules to survive

What ingredient necessary for life is missingWhat ingredient necessary for life is missingin all protobionts?in all protobionts?

No hereditary material that would ensureNo hereditary material that would ensure

continuity!continuity!



Did Microspheres Enclose the Earliest Cells?Did Microspheres Enclose the Earliest Cells?

CellCell--like microspheres can be formed by agitatinglike microspheres can be formed by agitatingproteins and lipids in a liquid medium. Each microsphereproteins and lipids in a liquid medium. Each microspherein this photo is about 5 micrometers (µm) in diameter.in this photo is about 5 micrometers (µm) in diameter.



Possible Steps in the Origin of LifePossible Steps in the Origin of Life

Protobionts and LiposomesProtobionts and Liposomes



Which Came First RNA or DNA?Which Came First RNA or DNA?

RNA!RNA!

RNA has the following properties:RNA has the following properties:

Less complex than DNALess complex than DNA

Less stable than DNALess stable than DNA

Has phenotype, can fold into diverseHas phenotype, can fold into diverse

shapesshapes Short strands of RNA can replicateShort strands of RNA can replicate

Ribozymes, show enzymes can be nonRibozymes, show enzymes can be non--protein moleculesprotein molecules



Experiments have proven that RNA canExperiments have proven that RNA canevolveevolve

The RNA world was slowly able to direct The RNA world was slowly able to direct

protein synthesis and preserve andprotein synthesis and preserve andcopy the genetic informationcopy the genetic information

As evolution continued different earlyAs evolution continued different earlycells showed varying success with lifecells showed varying success with life

One trend resulted in DNA as theOne trend resulted in DNA as theultimate hereditary materialultimate hereditary material

RNA worldRNA world DNA world!DNA world!



The Probable Origin of Mitochondria andThe Probable Origin of Mitochondria and

Chloroplasts in Eukaryotic CellsChloroplasts in Eukaryotic Cells



Symbiosis Within a Modern CellSymbiosis Within a Modern Cell The ancestors of the chloroplasts in today's plant cellsThe ancestors of the chloroplasts in today's plant cells

may have resembledmay have resembled ChlorellaChlorella, the green,, the green,photosynthetic, singlephotosynthetic, single--celled algae living symbioticallycelled algae living symbioticallywithin the cytoplasm of thewithin the cytoplasm of the ParameciumParamecium pictured here.pictured here.



In this format the RNA would be shared by all

competing RNA molecules



ORIGINS OF HEREDITY ORIGINS OF HEREDITY

RNA was probably the first genetic materialRNA was probably the first genetic material

Similar in structure to DNASimilar in structure to DNA

Short RNA polymers have been produced abioticallyShort RNA polymers have been produced abioticallyin the laboratoryin the laboratory

RNA possesses some catalytic activityRNA possesses some catalytic activity

Ribozymes discovered in 1980sRibozymes discovered in 1980s

Catalyze RNA splicing & synthesis of new RNACatalyze RNA splicing & synthesis of new RNA Natural selection at the molecular level has beenNatural selection at the molecular level has been

observed operating on RNA populations in theobserved operating on RNA populations in thelaboratorylaboratory



PROTOPROTO--CELLSCELLS

Chemical evolution ultimately led to theChemical evolution ultimately led to theformation of protoformation of proto--cellscells

MembraneMembrane--surrounded sacs containingsurrounded sacs containinggenetic material and metabolicallygenetic material and metabolically--activeactivemoleculesmolecules

Such structures have been experimentallySuch structures have been experimentallyproducedproduced

From these protoFrom these proto--cells, cells ultimatelycells, cells ultimatelyarosearose



EUKARYOTESEUKARYOTES

Eukaryotes evolved ~2.1 billion years agoEukaryotes evolved ~2.1 billion years ago

Possess several membranePossess several membrane--bound organellesbound organelles

Some originated from infoldings of the plasmaSome originated from infoldings of the plasmamembranemembrane

Some originated through endosymbiosisSome originated through endosymbiosis



ENDOSYMBIOSISENDOSYMBIOSISMitochondria & ChloroplastsMitochondria & Chloroplasts Surrounded by two membranesSurrounded by two membranes

Possess highly infolded inner membranesPossess highly infolded inner membranes

Inner membrane is involved in energyInner membrane is involved in energytransformationtransformation

Possess their own DNAPossess their own DNA

Organized in prokaryotic (bacterial) fashionOrganized in prokaryotic (bacterial) fashion

Possess ribosomesPossess ribosomes

70S (bacterial), not 80S (eukaryotic or70S (bacterial), not 80S (eukaryotic orarchaean)archaean)

Re roduce se arate from rest of cellRe roduce se arate from rest of cell



ENDOSYMBIOSISENDOSYMBIOSIS Both mitochondria and chloroplasts were onceBoth mitochondria and chloroplasts were once

free living organismsfree living organisms

Engulfed by early eukaryotic cellsEngulfed by early eukaryotic cells

Maintained rather than being digestedMaintained rather than being digested

EndosymbiontsEndosymbionts

Most genes have been lost or transferred to theMost genes have been lost or transferred to thenucleusnucleus

A few genes are retainedA few genes are retained At present, host cells cannot live without theirAt present, host cells cannot live without their

endosymbionts, and these endosymbiontsendosymbionts, and these endosymbiontscannot live without their host cellcannot live without their host cell

Other organellles are likely endosymbionts alsoOther organellles are likely endosymbionts also



Increased size evolved in response toIncreased size evolved in response topredationpredation

Increased size has drawbacksIncreased size has drawbacks

Lower surface areaLower surface area--toto--volume ratiovolume ratio

The evolution of multicellularity allowedThe evolution of multicellularity allowed

increased size without these limitationsincreased size without these limitations Multicellular algae arose ~1 billion years agoMulticellular algae arose ~1 billion years ago

Multicellular animals arose ~800 million yearsMulticellular animals arose ~800 million years

agoago

MULTICELLULARITY MULTICELLULARITY



TIMELINETIMELINE

1212 -- 15 b.y.a.15 b.y.a.

4.5 b.y.a.4.5 b.y.a.

3.8 b.y.a.3.8 b.y.a. 3.53.5 3.23.2

b.y.a.b.y.a.

2.5 b.y.a.2.5 b.y.a. 2.5 b.y.a.2.5 b.y.a.

2.1 b.y.a.2.1 b.y.a.

1 b.y.a.1 b.y.a.

Big bangBig bang

Origin of the earthOrigin of the earth

Origin of lifeOrigin of life Electron transport,Electron transport,

photosynthesisphotosynthesis

NonNon--cyclic photosynthesis, Ocyclic photosynthesis, O22

Cellular respirationCellular respiration

Origin of eukaryotesOrigin of eukaryotes

Origin of multicellularityOrigin of multicellularity



A Cosmic CalendarA Cosmic Calendar

(Pre(Pre--December Dates)December Dates)

Jan 1Jan 1 ( 15b yrs ago )( 15b yrs ago ) May 1May 1 ( 10.1b yrs( 10.1b yrs

ago )ago )

Sep 9Sep 9 ( 4.7b yrs ago )( 4.7b yrs ago ) Sep 14Sep 14 ( 4.5b yrs ago( 4.5b yrs ago

))

~Sep 25~Sep 25 ( ~ 4b yrs( ~ 4b yrs

ago )ago )

Big Bang.Big Bang.

Origin of the MilkyOrigin of the Milky

Way Galaxy.Way Galaxy.

Origin of the Solar Origin of the Solar

System.System.

Formation of theFormation of the

Earth.Earth.

Formation of theFormation of the

oldest rocks knownoldest rocks known

on Earth*.on Earth*.

Oct 2Oct 2 ( 3.7b yrs ago )( 3.7b yrs ago ) Oct 9Oct 9 ( 3.5b yrs ago )( 3.5b yrs ago ) ~Nov 1~Nov 1 ( ~2.5b yrs( ~2.5b yrs

ago )ago )

Nov 12Nov 12 ( 2.1b yrs( 2.1b yrs

ago )ago )

Nov 15Nov 15 ( 1.9b yrs( 1.9b yrs

ago )ago )

Origin of Life onOrigin of Life onEarth*.Earth*.

Date of oldest fossilsDate of oldest fossils

(bacteria and blue(bacteria and blue--green algae).green algae).

Invention of sex (byInvention of sex (by

micromicro--organisms).organisms).

Oldest fossilOldest fossil

photosyntheticphotosyntheticplants.plants.

Eukaryotes (firstEukaryotes (first

cells with nuclei)cells with nuclei)flourish.flourish.



A Cosmic CalendarA Cosmic Calendar

( December 31st )( December 31st )

~1:30 p.m.~1:30 p.m. ( 18.9m yrs( 18.9m yrs

ago )ago )

~10:30 p.m.~10:30 p.m. ( 2.7m yrs( 2.7m yrs

ago )ago )

11:00 p.m.11:00 p.m. ( 1.8m yrs( 1.8m yrs

ago )ago )

11:46 p.m.11:46 p.m. ( 420,000 yrs( 420,000 yrs

ago )ago )

Origin of Proconsul andOrigin of Proconsul and

Ramapithecus, probableRamapithecus, probableancestors of apes andancestors of apes and

men.men.

First humans.First humans. Widespread use of stoneWidespread use of stone

tools.tools.

Domestication of fire byDomestication of fire by

Peking man.Peking man.

11:56 p.m.11:56 p.m. ( 120,000 yrs( 120,000 yrs

ago )ago )

11:58 p.m.11:58 p.m. ( 60,000 yrs( 60,000 yrs

ago )ago )

11:59 p.m.11:59 p.m. ( 30,000 yrs( 30,000 yrs

ago )ago )

11:59:20 p.m.11:59:20 p.m. (20,000(20,000

yrs ago)yrs ago)

Beginning of most recentBeginning of most recent

glacial period.glacial period.

Seafarers settle Australia.Seafarers settle Australia. Extensive cave paintingExtensive cave painting

in Europe.in Europe.

Invention of agriculture.Invention of agriculture.



11:59:35 p.m.11:59:35 p.m.(12,500 yrs ago)(12,500 yrs ago)

11:59:50 p.m.11:59:50 p.m. ( 5000( 5000yrs ago )yrs ago )

11:59:51 p.m.11:59:51 p.m. ( 4500( 4500yrs ago )yrs ago )

11:59:52 p.m.11:59:52 p.m.(4000yrs ago)(4000yrs ago)

Neolithic civilisation;Neolithic civilisation;

first cities.first cities.

First dynasties inFirst dynasties in

Sumer, Ebla andSumer, Ebla and

Egypt; developmentEgypt; development

of astronomy.of astronomy.

Invention of theInvention of the

alphabet; Akkadianalphabet; Akkadian

Empire.Empire.

Hammurabic legalHammurabic legal

codes in Babylon;codes in Babylon;

Middle Kingdom inMiddle Kingdom in

Egypt.Egypt.

11:59:53 p.m.11:59:53 p.m. ( 3500( 3500

yrs ago )yrs ago )

11:59:54 p.m.11:59:54 p.m. ( 3000( 3000

yrs ago )yrs ago )

11:59:55 p.m.11:59:55 p.m. ( 2500( 2500

yrs ago )yrs ago )

11:59:56 p.m.11:59:56 p.m. ( 2000( 2000

yrs ago )yrs ago )

Bronze metallurgy;Bronze metallurgy;Mycenaean culture;Mycenaean culture;

Trojan War; OlmecTrojan War; Olmec

culture: invention of culture: invention of

the compass.the compass.

Iron metallurgy; FirstIron metallurgy; First

Assyrian Empire;Assyrian Empire;Kingdom of Israel;Kingdom of Israel;

founding of Carthagefounding of Carthage

by Phoenicia.by Phoenicia.

Asokan India; Ch'inAsokan India; Ch'in

Dynasty China;Dynasty China;Periclean Athens;Periclean Athens;

birth of Buddha.birth of Buddha.

Euclidean geometry;Euclidean geometry;

ArchimedeanArchimedeanphysics; Ptolemaicphysics; Ptolemaic

astronomy; Romanastronomy; Roman

Empire; birth of Empire; birth of

Christ.Christ.



11:59:57 p.m.11:59:57 p.m. ( 1500( 1500

yrs ago )yrs ago )

11:59:58 p.m.11:59:58 p.m. ( 1000( 1000

yrs ago )yrs ago )

11:59:59 p.m.11:59:59 p.m. ( 500( 500

yrs ago )yrs ago )

Now : The 1stNow : The 1st

second of second of NewNew

Year's DayYear's Day

Zero and decimalsZero and decimals

invented in Indianinvented in Indian

arithmetic; Romearithmetic; Rome

falls; Moslemfalls; Moslemconquests.conquests.

Mayan civilisation;Mayan civilisation;

Sung Dynasty China;Sung Dynasty China;

Byzantine empire;Byzantine empire;

Mongol invasion;Mongol invasion;Crusades.Crusades.

Renaissance inRenaissance in

Europe; voyages of Europe; voyages of

discovery fromdiscovery from

Europe and fromEurope and fromMing Dynasty China;Ming Dynasty China;

emergence of theemergence of the

experimental methodexperimental method

in science.in science.

WidespreadWidespread

development of development of

science andscience andtechnology;technology;

emergence of a globalemergence of a global

culture; acquisition of culture; acquisition of

the means for self the means for self--

destruction of thedestruction of the

human species; firsthuman species; firststeps in spacecraftsteps in spacecraft

planetary explorationplanetary exploration

and the search for and the search for

extraterrestrialextraterrestrial

intelligence.intelligence.

orign of life

Documents