2. Evolucion Unicelular

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Evolucin Celular

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Protoclula Protobionte

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en la tierra 3600 millones de aos 3600-3800 m.a. de micro-organismos

on los nicos s por muchos

atmosfrico fue bacterias tan an os todava del O2 ente

s tambin as y

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Early Earth showing volcanic activity and photosynthetic prokaryotes in dense mats

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Procariontes

Bacterias

Archeas

Dominan la tierra por muchos aos

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ArcheaCrenarchaeota (110C) Euryarchaeota producen metano Halfilos alta concentracin de sal

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Cianobacterias

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Cianobacteria viviente

Cianobacterias de Apex Chert (Australia) hace ms de 3 mil millones de aos (Brassier et al., 2002, Nature)

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Estromatolitos

Salar de LlamaraTuesday, April 17, 12

2003

Feb, 2007

Mar, 2007

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El medio ambiente condiciona la vida de los organismos en la naturaleza

Los organismos pueden modificar el medio ambiente en el cual viven

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Oxgeno atmosfrico comenz a acumularse hace 2700 millones de aos atrs

Fotosntesis

CO2 H2O

Fotosntesis se desarroll probablemente muy temprano en la vida de los procariontesPrimeras versiones de fotosntesis no usaron agua ni liberaron O2

Cianobacteria, organismos fotosintticos que rompen el agua y liberan O2 son los primeros responsables del aumento del oxgeno en la atmosfera.

O2

Acumulacin de O2 2700 m.a.Tuesday, April 17, 12

Muerte de procariontes anaerobios

Acumulacin de O2 2700 m.a.

Desarrollo de mecanismos de uso de O2 en procesos celularesTuesday, April 17, 12

?Tuesday, April 17, 12

Teora endosimbitica seriada

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Evidencias: Doble membrana (interna parecida a procariotas) DNA propio Genoma parecido a bacteria Sntesis de protenas (N-formyl-met/ /met ) Ribosomas Inhibicin de la sntesis proteica Fisin binariaTuesday, April 17, 12

Hatena(Dinoflagelados)

Nephroselmis(Protista)

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Hiptesis del fagocito primitivoProcarionte Ausencia de pared celular

Citoesqueleto

C. de DuveFormacin de vacuolas

Capacidad fagocticaEndosimbiosis Formacin del ncleo

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Problema: Amplia diversidad de organismos... como lograr hacer un mapa evolutivo?

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Problema: Amplia diversidad de organismos... como lograr hacer un mapa evolutivo?

Similitudes Todos presentan vas metablicas comunes (gliclisis) DNA RNA Protenas Cdigo gentico comn Todos tienen una membrana

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Todos los organismos ensamblan protenas...

rRNACarl Woese

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Nuevo arbol de la vida basado en pequea subunidad rRNA (Woese 1996)

Consecuencias...

Relacin cercana entre eucariontes y archeas Menor distancia entre plantas y animalesTuesday, April 17, 12

(Last Universal Common Ancestor)Tuesday, April 17, 12

LUCA

Arbol a partir de genes que sostiene que Archaea y Eucarya sonacercanos gen Arbol partir de en relacin sostiene que Arc a Bacteria que

y Eucarya son cercan en relacin a Bacteri

bol a partir de genes que stiene que Archaea and cteria son cercanos en Arbol a partir de genes que acion a Eucarya sostiene que Archaea and Bacteria son cercanos en relacion a EucaryaTuesday, April 17, 12

cos en Archaea

Transferencia horizontal de genes en la evolucin

gen delala enzima gen de enzima eductasa en en HMGCoA reductasa grupos de Archaea Archaea

haea reemplaz r uno de

nalisis publicado en 1998, 2003

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stro comn de toda la vida (cenancestor) fue una Cenancestor nidad de especies de especies que intercambiaban genes que intercambiaban genes unos co Comunidad s

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Archea

Replicacin Transcripcin Traduccin Protoeucariota Eucariota 1.5m.a

Bacteria

Metabolismo

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Innovaciones en EUCARIONTES Ncleo? Filamentos?

PlanctomycetesTuesday, April 17, 12

Innovaciones en EUCARIONTES

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GENETIC INFORMATION IN EUCARYOTES

ProtistasI.

33

especially, is often elaborate and includes such structures as sensory bristles, photoreceptors, sinuously beating cilia, leglike appendages, mouth parts, stingTuesday, April 17, 12 ing darts, and musclelike contractile bundles. Although they are single cells,

Figure 141 An assortment of protists: a small sample of an extremely diverse class of organisms. The drawings are done to different scales, but in each case

GENETIC INFORMATION IN EUCARYOTES

33

I.

especially, is often elaborate and includes such structures as sensory bristles, photoreceptors, sinuously beating cilia, leglike appendages, mouth parts, stinging darts, and musclelike contractile bundles. Although they are single cells, protozoa can be as intricate, as versatile, and as complex in their behavior as many multicellular organisms (see Figure 132). In terms of their ancestry and DNA sequences, protists are far more diverse than the multicellular animals, plants, and fungi, which arose as three comparatively late branches of the eucaryotic pedigree (see Figure 121). As with procaryotes, humans have tended to neglect the protists because they are microscopic. Only now, with the help of genome analysis, are we beginning to understand their positions in the tree of life, and to put into context the glimpses these strange creatures offer us of our distant evolutionary past.

Figure 141 An assortment of protists: a small sample of an extremely diverse class of organisms. The drawings are done to different scales, but in each case the scale bar represents 10 mm. The organisms in (A), (B), (E), (F), and (I) are ciliates; (C) is a euglenoid; (D) is an amoeba; (G) is a dinoflagellate; (H) is a heliozoan. (From M.A. Sleigh, Biology of Protozoa. Cambridge, UK: Cambridge University Press, 1973.)

A Yeast Serves as a Minimal Model EucaryoteThe molecular and genetic complexity of eucaryotes is daunting. Even more than for procaryotes, biologists need to concentrate their limited resources on a few selected model organisms to fathom this complexity. To analyze the internal workings of the eucaryotic cell, without the additional problems of multicellular development, it makes sense to use a species that is unicellular and as simple as possible. The popular choice for this role of minimal model eucaryote has been the yeast Saccharomyces cerevisiae (Figure 142)the same species that is used by brewers of beer and bakers of bread. S. cerevisiae is a small, single-celled member of the kingdom of fungi and thus, according to modern views, at least as closely related to animals as it is to plants. It is robust and easy to grow in a simple nutrient medium. Like other fungi, it has a tough cell wall, is relatively immobile, and possesses mitochondria but not chloroplasts. When nutrients are plentiful, it grows and divides almost as

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