Formation of our Universe 10-20 billion years ago Formation of our solar system and Earth 4.6 billion years ago Cooling of Earth, formation of oceans,

Formation of our Universe10-20 billion years ago

Formation of our solar system and Earth4.6 billion years ago

Cooling of Earth, formation of oceans, hospitable environs3.9 billion years ago

Formation of Cenancestor3.6 to 4.1 billion years ago

Existence of diverse domains Bacteria, Eukarya and Archaea 2.5 billion years ago

common ancestor

(Cenancestor)

Bacteria

Eukarya

Archaea

Early Earth and Origins of Life

1. Abiotic synthesis (inorganic > organic)

Oparin & Haldane hypothesis (1920s)Urey & Miller (1953)

• Joining of monomers > polymersFox (1950s-60s)

• Packaging of protobiontsOparin hypothesis (1920s)Fox (1950s-60s)

• Self-replicating moleculesCech (1980s)Altman (1980s)

Hypotheses of Early Life: Cenancestor formation

(4 main phases)







(4 main phases)

Abiotic synthesis: Early Earth environment

•Oparin & Haldane Hypothesis (1920s)

•No O2

•Reducing environment favors synthesis

•CO2 NH3 H2 H2O CH4 H2S

•Lightning, UV irradiation, etc.

•“Primordial Soup” hypothesis

Stanley Miller, Age 23

Miller and Urey, 1953

• Bottom flask heated > vaporization

• Electric sparks applied to top flask

• Ran for 1 week• Results:

• Water became pink, then red, and turbid

• Analysis of contents reveals organic compounds• amino acids (alanine and

glycine)• sugars• lipids• building blocks of nucleic

acids







(4 main phases)

Sydney Fox: Simple polymers (1950s)

•amino acids (monomers)

•Heat

•Hot sand, clay, rock

•polypeptides (polymers)

*dripped amino acids over hot sand, clay, rock and found that given the proper conditions, monomers would join to form polymers*in same manner were able to form proteinoids (a type of protobiont) as outlined in next section





• Self-replicating moleculesCech (1980s) Altman (1980s)


(4 main phases)

Protobionts: aggregates of abiotically produced molecules surrounded by

membrane•Oparin (1920s) coined the term

• “bubble hypothesis”

•Sydney Fox (1950s-60s) demonstrated with proteins as “membrane” (proteinoids)

•Maintain internal chemical environment separate from surroundings

•Some properties associated with life

• reproduction- can “duplicate” & “divide”

• “metabolism”- can take up substances; can set up simple metabolic reactions inside

Protobionts

coacervates, proteinoids, micelles, liposomes, microspheres

•synonyms and different names depending on what “membrane” is made of:

Liposome formation

•Amphiphilic lipids form micelles and liposomes

•Hydrophilic (water-loving) heads and hydrophobic (water-hating) tails self-assemble in agitated H2O

•Can grow and shrink in the presence of salts

Protobionts: fossil evidence3.5 billion years ago





• Self-replicating moleculesCech (1980s) Altman (1980s)


(4 main phases)

Ribozymes = RNA as an enzyme

•RNA-directed catalysis discovered in nature (1980s)

•Tom Cech - self splicing introns

•Syndey Altman - tRNA cleavage

Ribozymes & the “RNA World”

Self-replicating Ribozyme (2001)“RNA polymerase ribozyme”

made in lab“R

• RNA may have been the first genetic material

• RNA simpler than DNA

• error-prone polymerization produces “mutations”- diversity in “offspring”

• natural selection of “offspring” with more efficient catalysis leads to “evolution”

• idea that enzymatic activity appears first and specificity evolves later



Modern precedent for idea of RNA as self-replicating genetic material

• RNA viruses: RNA as sole genetic material (no DNA intermediates)

• RNA molecules involved in many types of polymerization in “modern” cells

• Telomere (DNA end structures) replication

• Ribosome and tRNA (Translation)

Formation of our Universe10-20 billion years ago

Formation of our solar system and Earth4.6 billion years ago

Cooling of Earth, formation of oceans, hospitable environs3.9 billion years ago

Formation of Cenancestor3.6 to 4.1 billion years ago

Existence of diverse domains Bacteria, Eukarya and Archaea 2.5 billion years ago

common ancestor

(Cenancestor)

Bacteria

Eukarya

Archaea

Early Earth and Origins of Life

What is missing from early Earth atmosphere that we need in order to

progress to the 3 Domains?

Hypothesis: Going from Cenancestor to 3 Domains

I. Prokaryotes oxygenate the atmosphere

•cellular metabolism evolved in prokaryotes•first organisms are chemoheterotrophs

•no oxygen in atmosphere (so anaerobic)•only food is organic matter in primordial soup



•second to evolve are simple autotrophs•give off oxygen as by product•this leads to the oxygenation of atmosphere•some hypothesize that these were photosynthetic Cyanobacteria-like organisms•third to evolve are heterotrophs that use oxygen (aerobic)

This is the Heterotroph Hypothesis:

chemoheterotrophs > autotrophs > heterotrophs no O2 present produce O2 use O2



CytoplasmDNA

Plasmamembrane

Ancestralprokaryote

Infolding ofplasma membrane

Endoplasmicreticulum

Nuclear envelope

Nucleus

Engulfingof aerobic

heterotrophicprokaryote

Cell with nucleusand endomembranesystem

Mitochondrion

Ancestralheterotrophiceukaryote

Plastid

Mitochondrion

Engulfing ofphotosyntheticprokaryote insome cells

Ancestral Photosyntheticeukaryote

How we got organelles-

the hypothesis


II. Going from prokaryotes to eukaryotes



•First, membrane in-folding created endoplasmic reticulum and nucleus



•second, endosymbiosis led to formation of mitochondria and chloroplasts

Endosymbiotic Theory

mitochondria from

heterotrophic (aerobic)

prokaryote

chloroplasts from

photosynthetic prokaryote

(Cyanobacteria?)

Modern evidence for Endosymbiotic Theory

Mitochondria and chloroplasts are prokaryote-like

Formation of our Universe 10-20 billion years ago Formation of our solar system and Earth 4.6 billion years ago Cooling of Earth, formation of oceans,

Documents

s altman

s lightning

s urey miller

s hypotheses of early

s amino acids monomers

monomers polymers fox

formation of cenancestor

cenancestor formation