2. 2. The origin of life The origin of life and first organismsand first organisms

What do you know about it?What do you know about it?

Silverfishes (Silverfishes (Lepisma)Lepisma) are little insects very are little insects very usual in our houses. We usual in our houses. We find them frequently in find them frequently in places where we don’t places where we don’t make a daily cleaning, make a daily cleaning, that is under the fridge that is under the fridge our among the books. Do our among the books. Do you think it would be you think it would be easy to prove they don’t easy to prove they don’t originate spontaneously originate spontaneously from dirty clothes?from dirty clothes?

Do you think it is possible that life on Do you think it is possible that life on Earth came from outer spaceEarth came from outer space??

The origin of life on the WEBThe origin of life on the WEB

Interview to Lynn MargulisInterview to Lynn Margulishttp://www.uv.es/metode/numero31/12_31.htmlhttp://www.uv.es/metode/numero31/12_31.html

Interview to Stanley MillerInterview to Stanley Millerhttp://www.uv.es/metode/numero39/29_39.htmhttp://www.uv.es/metode/numero39/29_39.htm

Signals of life in a Martian meteoriteSignals of life in a Martian meteoritehttp://www.espacial.org/planetarias/exobiologia/http://www.espacial.org/planetarias/exobiologia/alh84001.htmalh84001.htm

Understanding what life is?Understanding what life is?

Life is carbon, oxygen, nitrogen, hydrogen…Life is carbon, oxygen, nitrogen, hydrogen… Life is water, lots of water and mineral saltsLife is water, lots of water and mineral salts Life are proteins, nucleic acids, lipids and Life are proteins, nucleic acids, lipids and

carbohydratescarbohydrates But, why don’t we rather ask...But, why don’t we rather ask...

HOW DOES LIFE BEHAVE?HOW DOES LIFE BEHAVE?

Life propertiesLife properties

AUTOPOIESISAUTOPOIESIS: self renewal: self renewal METABOLISMMETABOLISM: chemical changes and energy : chemical changes and energy

consumptionconsumption REPRODUCTIONREPRODUCTION: new organisms appear that : new organisms appear that

accumulate the progenitors genetic material. accumulate the progenitors genetic material. Mutations can happenMutations can happen

EVOLUTIONEVOLUTION: it has changed since the origins. : it has changed since the origins. Innovations are promoted by natural selectionInnovations are promoted by natural selection

Pasteur experimentPasteur experiment

Louis Pasteur(1822-1895)

The Miller-Urey experimentThe Miller-Urey experiment

(1953)(1953)Methane, ammonia, Methane, ammonia, hydrogen,hydrogen,water steamwater steam

The products are The products are AMINOACIDSAMINOACIDS

The The Ponnamperuma Ponnamperuma

experimentsexperiments

(1963)(1963) Hydrocyanic acid, ammonia,Hydrocyanic acid, ammonia,

methane, water steam methane, water steam (Berkeley´s Cyclotron)(Berkeley´s Cyclotron)

Results: ADENINE, RIBOSE Results: ADENINE, RIBOSE and DESOXYRIBOSEand DESOXYRIBOSE

The first stages of life: The first stages of life: hydrothermal sources at hydrothermal sources at

the oceanic riftsthe oceanic rifts

Stromatolites (pre-cambrian – more than 1000 million years ago) Stromatolites (pre-cambrian – more than 1000 million years ago) (Glacier National Park – Montana – USA)(Glacier National Park – Montana – USA)

From Greek From Greek στρωμαστρωμα stroma = bed/carpet and stroma = bed/carpet and λιθολιθο litho = stone. They are litho = stone. They are stratified structures with different shapes, formed by trapping and binding stratified structures with different shapes, formed by trapping and binding carbonate particles by cyanobacteria in shallow waters, that release oxygen carbonate particles by cyanobacteria in shallow waters, that release oxygen during photosynthesis, and remove from the atmosphere great amounts of during photosynthesis, and remove from the atmosphere great amounts of carbon dioxide to use it in part to build the stromatolites.carbon dioxide to use it in part to build the stromatolites.

Intertidal zones

Modern stromatolites in Shark Bay (Western Australia)

Outer spaceOuter space Analyzing chemical composition of Analyzing chemical composition of

meteorites and comets has proved that they meteorites and comets has proved that they include organic substances related to lifeinclude organic substances related to life

There were very frequent impacts at the age There were very frequent impacts at the age immediately after the planet formationimmediately after the planet formation

That is why some scientists consider very That is why some scientists consider very suitable that suitable that basic molecules of life basic molecules of life could could have come from outer spacehave come from outer space

Other scientists have daring ideas and Other scientists have daring ideas and propose that meteorites could have also propose that meteorites could have also transported, besides some organic molecules, transported, besides some organic molecules, tiny living beings tiny living beings similar to modern bacteria, similar to modern bacteria, and after reaching the Earth they would have and after reaching the Earth they would have started to reproduce and evolvestarted to reproduce and evolve

In that case, we would all be “extraterrestrialIn that case, we would all be “extraterrestrial””

Comet Halley

Hyper-thermophile organismsHyper-thermophile organisms1.1. If the first forms of cellular life appeared near to If the first forms of cellular life appeared near to

hydrothermal sources they should be able to resist hydrothermal sources they should be able to resist high temperatures, as present day hyper-high temperatures, as present day hyper-thermophile bacteria dothermophile bacteria do

2.2. Advantages:Advantages: to avoid the discussion about the to avoid the discussion about the composition of early atmosphere. It is not composition of early atmosphere. It is not important whether atmosphere was poorer or important whether atmosphere was poorer or richer in methane, ammonia or carbon oxides. richer in methane, ammonia or carbon oxides. Besides, oceanic water would have acted as an Besides, oceanic water would have acted as an effective protecting shelter from numerous effective protecting shelter from numerous meteorite impacts and comets usual in the early meteorite impacts and comets usual in the early days of earth’s historydays of earth’s history

Inconvenients: Inconvenients: there are few experimental proofs there are few experimental proofs of the process that lead to the origin of organic of the process that lead to the origin of organic molecules and their polymers, starting from sulfur molecules and their polymers, starting from sulfur waters emerged in submarine eruptionswaters emerged in submarine eruptions

Hydrothermal source atYellowstone (USA), the first place wherehyper-thermophileorganisms were found

Life clockLife clock

A short history of life on earthA short history of life on earth Between 3900 and 3500 m.y. ago, the first primitive cell vas Between 3900 and 3500 m.y. ago, the first primitive cell vas

originated. All modern living beings come from it (LUCA)originated. All modern living beings come from it (LUCA) It was an aqueous, PROKARYOTE and HETEROTROPH It was an aqueous, PROKARYOTE and HETEROTROPH

cell, with an ANAEROBIC metabolismcell, with an ANAEROBIC metabolism The lack of food led to the selection of a class of prokaryote The lack of food led to the selection of a class of prokaryote

PHOTOSYNTHESIZERS, AUTOTROPH organisms that toke PHOTOSYNTHESIZERS, AUTOTROPH organisms that toke profit of light and released hydrogen from waterprofit of light and released hydrogen from water

They were the ancestors of modern CYANOBACTERIA who They were the ancestors of modern CYANOBACTERIA who dominated the seas and enriched the atmosphere with the dominated the seas and enriched the atmosphere with the oxygen released by breaking apart the water moleculeoxygen released by breaking apart the water molecule

The increase of oxygen, that was toxic for most of the living The increase of oxygen, that was toxic for most of the living organisms at the time, selected those organisms that organisms at the time, selected those organisms that mutated, became resistant to oxygen and finally developed mutated, became resistant to oxygen and finally developed AEROBIC pathwaysAEROBIC pathways

Between 1000 and 700 m.y. ago the atmospheric oxygen Between 1000 and 700 m.y. ago the atmospheric oxygen reached the present time levelreached the present time level

The first cellular organismsThe first cellular organisms

Proto-cellProto-cell CyanobacteriaCyanobacteria

The origin of eukaryotesThe origin of eukaryotes 1500 m.y. ago the bacterium 1500 m.y. ago the bacterium ThermoplasmaThermoplasma

joined a joined a SpirochaeteSpirochaete to give a permanent to give a permanent SYMBIOSIS that formed a new model of cellular SYMBIOSIS that formed a new model of cellular organization: the EUKARYOTE cellorganization: the EUKARYOTE cell

The eukaryote cell has a well defined nucleus The eukaryote cell has a well defined nucleus separated from the rest of the cell by a double separated from the rest of the cell by a double layer and an inner structure supported by layer and an inner structure supported by microtubulesmicrotubules

The union of a third bacterium produced what we The union of a third bacterium produced what we know as MITOCHONDRIA what let them make know as MITOCHONDRIA what let them make good use of oxygengood use of oxygen

This hypothesis is known as SERIAL This hypothesis is known as SERIAL ENDOSYMBIOSISENDOSYMBIOSIS

Early organismsEarly organisms

SpirochaeteSpirochaete GiardiaGiardia

Life at the seas and on dry landLife at the seas and on dry land

Life adapted to shallower spaces and Life adapted to shallower spaces and progressively to the aerial and terrestrial progressively to the aerial and terrestrial environment, even though there were some environment, even though there were some obstacles:obstacles:

lack of water lack of water drying up dangerdrying up dangerhigh light intensityhigh light intensityexcess of oxygenexcess of oxygenlack of sustenancelack of sustenancedifficulties to movedifficulties to move

The early The early earthearth

800 m.y. ago some unicellular organisms started 800 m.y. ago some unicellular organisms started to inhabit the intertidal zones, some of which were to inhabit the intertidal zones, some of which were successful and adapted by means of structures successful and adapted by means of structures that let them avoid losing waterthat let them avoid losing water

The first multicellular organisms appeared some The first multicellular organisms appeared some 670 m.y. ago and between 600 and 500 m.y. the 670 m.y. ago and between 600 and 500 m.y. the Cambrian explosion happenedCambrian explosion happened

The ancestors of arthropods and chordate (The ancestors of arthropods and chordate (PikaiaPikaia) ) appeared at the seaappeared at the sea

The first terrestrial plants exist since 450 m.y. ago. The first terrestrial plants exist since 450 m.y. ago. The invention of seeds allowed them to overcome The invention of seeds allowed them to overcome the danger of drying upthe danger of drying up

The first terrestrial animals exist since 400 m.y. The first terrestrial animals exist since 400 m.y. ago and are quite similar to modern little ago and are quite similar to modern little arthropodsarthropods

Sea fossilsSea fossils PikaiaPikaia

DickinsoniaDickinsonia

KimberellaKimberella

SprigginaSpriggina

Rebuilding the stepsRebuilding the steps

1.1. Decisive facts in time:Decisive facts in time:

2.2. Concentration of oxygen in atmosphere stabilized Concentration of oxygen in atmosphere stabilized between 1 000 and 1 700 million years. This between 1 000 and 1 700 million years. This event, added to the presence of the ozone layer, event, added to the presence of the ozone layer, protecting from ultraviolet radiation of the sun, protecting from ultraviolet radiation of the sun, made possible to begin the colonization of made possible to begin the colonization of temporary dry zones by aerobic unicellular temporary dry zones by aerobic unicellular organisms, some 800 million years agoorganisms, some 800 million years ago

Pre-cambrian unicellularorganisms> 570 m.y.

Modifying life: Modifying life: genetic engineeringgenetic engineering

Human beings came to the stage 500 million Human beings came to the stage 500 million years after little and soft years after little and soft Pikaia.Pikaia. Lost in one Lost in one of the many branches of the life tree, our of the many branches of the life tree, our species is quite remarkable: we have the species is quite remarkable: we have the ability to ask us about oneself and about our ability to ask us about oneself and about our surrounding worldsurrounding world

The last 60 years, this ability has led to The last 60 years, this ability has led to reveal the nature of genetic material, the reveal the nature of genetic material, the DNA, and so how to modify itDNA, and so how to modify it

Genetic engineering Genetic engineering consists of manipulating consists of manipulating and modifying genetic information, i.e, the DNA and modifying genetic information, i.e, the DNA of any living being, either a bacterium, a plant of any living being, either a bacterium, a plant or an animal, by introducing genes from outer or an animal, by introducing genes from outer organisms or modifying its own genesorganisms or modifying its own genes

It actually refers to the redesign of the vital It actually refers to the redesign of the vital program of any living beingprogram of any living being

It has been developed thanks to natural It has been developed thanks to natural processes from the microorganisms processes from the microorganisms

Many bacteria have fragments of genetic Many bacteria have fragments of genetic material, called material, called plasmidsplasmids, used to , used to exchange genetic informationexchange genetic information

Plasmids can replicate independently of the Plasmids can replicate independently of the chromosomal DNA of the bacteriachromosomal DNA of the bacteria

There are also the There are also the retrovirusretrovirus, whose , whose genetic material can melt with the infected genetic material can melt with the infected cell’s DNAcell’s DNA

Plasmids and viruses used in genetic Plasmids and viruses used in genetic engineering are called engineering are called vectorsvectors, as they drive , as they drive the introduction of new genetic informationthe introduction of new genetic information

In the 70’s of last century some enzymes In the 70’s of last century some enzymes were discovered belonging to the bacteria, were discovered belonging to the bacteria, called called restriction enzymesrestriction enzymes, devoted to , devoted to destroy the strange DNA invading the cellsdestroy the strange DNA invading the cells

These are some sort of “genetic scissors” These are some sort of “genetic scissors” able to cut segments of DNA in precise able to cut segments of DNA in precise placesplaces

Nowadays, insulin used by diabetic patients Nowadays, insulin used by diabetic patients or the growing hormone are obtained by or the growing hormone are obtained by genetic engineering. The human gene is genetic engineering. The human gene is introduced in bacteria that produce insulin or introduced in bacteria that produce insulin or the growing hormonethe growing hormone

Transgenic vegetablesTransgenic vegetables

Vegetables have a property that makes the Vegetables have a property that makes the applications of genetic engineering easier: applications of genetic engineering easier: cells from some species easily regenerate cells from some species easily regenerate and let grow an adult plant, so this way and let grow an adult plant, so this way changes made in these cells can achieve changes made in these cells can achieve the whole plant, even sexual cells. By the whole plant, even sexual cells. By means of these process changes will also means of these process changes will also be transmitted to their offspringbe transmitted to their offspring

Genetic engineering applied to plants is bound Genetic engineering applied to plants is bound to achieve better yield crops, control ripening to achieve better yield crops, control ripening and preservation of fruits, obtain resistance to and preservation of fruits, obtain resistance to plagues and herbicides or produce therapeutic plagues and herbicides or produce therapeutic substancessubstances

Dealing with transgenic vegetables, there is Dealing with transgenic vegetables, there is controversy for sure. Its advantages are controversy for sure. Its advantages are important, because of the increasing needs for important, because of the increasing needs for feeding mankind; but there are also some feeding mankind; but there are also some uncertain risks that entice to debateuncertain risks that entice to debate

Which is the side effect of these products for Which is the side effect of these products for human consumption?human consumption?

Genes from crops can go to plants in Genes from crops can go to plants in ecosystems by hybridization? Which could be ecosystems by hybridization? Which could be the consequences of this fact?the consequences of this fact?

Is there a risk to lose biodiversity?Is there a risk to lose biodiversity? Current legislation commits the manufacturer Current legislation commits the manufacturer

of any food with transgenic ingredients or with of any food with transgenic ingredients or with genetically modified ones to put on record genetically modified ones to put on record this aspect on the labelthis aspect on the label

Artificial lifeArtificial life To make artificial life at the laboratory from To make artificial life at the laboratory from

inert matter has always stimulated human inert matter has always stimulated human imagination. But if one day it is achieved, imagination. But if one day it is achieved, artificial life will have nothing to do with artificial life will have nothing to do with Frankenstein nor any other similar Frankenstein nor any other similar creatures. It will be nothing but bacteriacreatures. It will be nothing but bacteria

Some biotechnological industries rub their Some biotechnological industries rub their hands before the commercial expectations hands before the commercial expectations opened by the chance of creating bacteria opened by the chance of creating bacteria by orderby order

Bacteria able to digest carbon dioxide and Bacteria able to digest carbon dioxide and residues and produce biofuels or drugs residues and produce biofuels or drugs could be designedcould be designed

Recently, the research team at Craig Venter Recently, the research team at Craig Venter Institute, in Rockville (USA), has synthetized Institute, in Rockville (USA), has synthetized the whole chromosome of the whole chromosome of Mycoplasma Mycoplasma genitaliumgenitalium, a very tiny bacterium with one , a very tiny bacterium with one single chromosome including only 484 single chromosome including only 484 genesgenes

In order to get it they have synthetized short In order to get it they have synthetized short artificial fragments of DNAartificial fragments of DNA

Then the fragments have been joined Then the fragments have been joined together and copied inside the bacterium together and copied inside the bacterium Escherichia coliEscherichia coli and a yeast and a yeast

So, many artificial replicas of the original So, many artificial replicas of the original bacterial chromosome have been obtained. bacterial chromosome have been obtained. The next step is to make living cells of The next step is to make living cells of MycoplasmaMycoplasma from the synthetic from the synthetic chromosomechromosome

The artificial synthesis of one chromosome, The artificial synthesis of one chromosome, even though it is a very important step, is even though it is a very important step, is not yet by any means the making of artificial not yet by any means the making of artificial life at the laboratorylife at the laboratory

One chromosome is only a handbook and to One chromosome is only a handbook and to consider that we have made artificial life we consider that we have made artificial life we also need the rest of the cell components also need the rest of the cell components coming from the genetic information hold in coming from the genetic information hold in the synthetic chromosomethe synthetic chromosome

PhytoremediationPhytoremediation

1.1. Phytoremediation is the use of genetically Phytoremediation is the use of genetically modified plants in order to effectively modified plants in order to effectively degrade some contaminant agents, specially degrade some contaminant agents, specially heavy metalsheavy metals

2.2. Gene Gene merA merA is obtained from bacteria is obtained from bacteria containing it (containing it (E. coliE. coli); it’s taken from a ); it’s taken from a plasmid from another bacterium able to plasmid from another bacterium able to infect vegetable cells (infect vegetable cells (AgrobacteriumAgrobacterium) and ) and inserted the gene inserted the gene merAmerA

3.3. The new recombinant plasmid is inserted in The new recombinant plasmid is inserted in bacteria infecting vegetable cells bacteria infecting vegetable cells ((AgrobacteriumAgrobacterium) and cultivation of these ) and cultivation of these bacteria is added to the tulip tree stems, bacteria is added to the tulip tree stems, they are infected and the gene they are infected and the gene merA merA is is incorporated to DNA in its cellsincorporated to DNA in its cells

4.4. It seems difficult to save that transgenic It seems difficult to save that transgenic plants be hybridized with similar species. plants be hybridized with similar species. Detractors to the use of transgenic plants Detractors to the use of transgenic plants argue that this fact could alter ecosystems in argue that this fact could alter ecosystems in an irreversible wayan irreversible way

5.5. On the other hand, they assure that there is On the other hand, they assure that there is not enough guarantee that no harmful not enough guarantee that no harmful effects will happen to human health, for effects will happen to human health, for instance the increase of allergies, or the instance the increase of allergies, or the decrease of planetary biodiversitydecrease of planetary biodiversity

Tulip(Liriodendron tulipifera)

To learn moreTo learn more Terrades, J. Terrades, J. Una biografia del món: de Una biografia del món: de

l’origen de la vida al col·lapse ecològic. l’origen de la vida al col·lapse ecològic. Barcelona: Ed. Columna, 2006Barcelona: Ed. Columna, 2006

Margulis, L & Dolan M. Margulis, L & Dolan M. Els inicis de la vida: Els inicis de la vida: l’evolució en l’era precambriana. l’evolució en l’era precambriana. València: València: Bromera, 2006Bromera, 2006

Vannier, J. Vannier, J. “Orígenes de la biodiversidad “Orígenes de la biodiversidad biológica”. biológica”. Investigación y CienciaInvestigación y Ciencia,, núm. núm. 379 (2008), pàg. 80-87379 (2008), pàg. 80-87

González, A. González, A. Astrobiología. Astrobiología. Madrid: Equipo Madrid: Equipo Sirius, 2004Sirius, 2004

Nottingham, S. Nottingham, S. Come tus genes: cómo los Come tus genes: cómo los alimentos transgénicos están en nuestra alimentos transgénicos están en nuestra dietadieta. . Barcelona: Paidós Ibérica, 2004Barcelona: Paidós Ibérica, 2004

Villalobos, V. Villalobos, V. Los transgénicos. Los transgénicos. Mèxic: Mèxic: Mundi-Prensa, 2007Mundi-Prensa, 2007