Download AP Bio Early Earth 2009

Early Earth and Origins of Life
Formation of our Universe
10-20 billion years ago
Bacteria
Eukary
Archaea
a
Formation of our solar system
and Earth
4.6 billion years ago
Cooling of Earth, formation of
oceans, hospitable environs
3.9 billion years ago
Formation of cenancestor
(LUCA)
3.6 to 4.1 billion years ago
Emergence of 3 Domains:
Archaea, Bacteria, Eukarya
2.5 billion years ago
common ancestor
(cenancestor/LUCA)
Hypotheses of Early Life: cenancestor
formation
(4 synthesis
main phases)
1. Abiotic
(inorganic -->
organic)
Oparin & Haldane hypothesis
(1920s)
Urey & Miller (1953)
• Joining of monomers > polymers
Fox (1950s-60s)
• Packaging of protobionts
Oparin’s hypothesis (1920s)
Fox (1950s-60s)
• Self-replicating molecules
Cech (1980s)
Altman (1980s)
Hypotheses of Early Life: Cenancestor
formation
(4 main phases)
1. Abiotic synthesis (inorganic > organic)
Oparin & Haldane hypothesis
(1920s)
Urey & Miller (1953)
• Joining of monomers > polymers
Fox (1950s-60s)
• Packaging of protobionts
Oparin hypothesis (1920s)
Fox (1950s-60s)
• Self-replicating molecules
Cech (1980s)
Altman (1980s)
Abiotic synthesis: Early Earth
environment
• Oparin & Haldane Hypothesis (1920s)
• No O
• Reducing environment favors synthesis
• CO NH H H O CH H S
• Lightning, UV irradiation, etc.
• “Primordial Soup” hypothesis
2
2
3
2
2
4
2
Miller and Urey,
• Bottom flask 1953
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
Stanley Miller, Age 23
Hypotheses of Early Life: Cenancestor
formation
(4 main phases)
1. Abiotic synthesis (inorganic > organic)
Oparin & Haldane hypothesis
(1920s)
Urey & Miller (1953)
• Joining of monomers > polymers
Fox (1950s-60s)
• Packaging of protobionts
Oparin hypothesis (1920s)
Fox (1950s-60s)
• Self-replicating molecules
Cech (1980s)
Altman (1980s)
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
Hypotheses of Early Life: Cenancestor
formation
(4 main phases)
1. Abiotic synthesis (inorganic > organic)
Oparin & Haldane hypothesis
(1920s)
Urey & Miller (1953)
• Joining of monomers > polymers
Fox (1950s-60s)
• Packaging of protobionts
Oparin hypothesis (1920s)
Fox (1950s-60s)
• Self-replicating molecules
Cech (1980s)
Altman (1980s)
•
•
•
•
Protobionts: aggregates of abiotically
produced molecules surrounded by
Oparin (1920s) coined the term “bubble
membrane
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
•synonyms and different names depending on what
“membrane” is made of:
coacervates, proteinoids, micelles, liposomes, microspheres
Liposome formation
• Amphiphilic lipids form micelles and
liposomes
• Hydrophilic (water-loving) heads and
hydrophobic (water-hating) tails selfassemble in agitated H2O
• Can grow and shrink in the presence of
salts
Protobionts: fossil evidence
3.5 billion years ago
Hypotheses of Early Life: Cenancestor
formation
(4 main phases)
1. Abiotic synthesis (inorganic > organic)
Oparin & Haldane hypothesis
(1920s)
Urey & Miller (1953)
• Joining of monomers > polymers
Fox (1950s-60s)
• Packaging of protobionts
Oparin hypothesis (1920s)
Fox (1950s-60s)
• Self-replicating molecules
Cech (1980s)
Altman (1980s)
Ribozymes & the “RNA World”
Ribozymes = RNA as an enzyme
• RNA-directed catalysis discovered in
nature (1980s)
• Tom Cech - self splicing introns
• Syndey Altman - tRNA cleavage
Self-replicating Ribozyme (2001)
“RNA polymerase ribozyme” made in
lab
“R
Ribozymes & the “RNA World”
•
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
Ribozymes & the “RNA World”
Modern precedent for idea of RNA as selfreplicating 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)
What is missing from early Earth
atmosphere that we need in order to
progress to the 3 Domains?
Early Earth and Origins of Life
Formation of our Universe
10-20 billion years ago
Bacteria
Eukary
Archaea
a
Formation of our solar system
and Earth
4.6 billion years ago
Cooling of Earth, formation of
oceans, hospitable environs
3.9 billion years ago
Formation of cenancestor
(LUCA)
3.6 to 4.1 billion years ago
Emergence of 3 Domains:
Archaea, Bacteria, Eukarya
2.5 billion years ago
common ancestor
(cenancestor/LUCA)
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
Domains
I. Prokaryotes oxygenate the atmosphere
•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)
Hypothesis: Going from Cenancestor to 3
Domains
I. Prokaryotes oxygenate the atmosphere
This is the Heterotroph Hypothesis:
chemoheterotrophs > autotrophs > heterotrophs
no O2 present
produce O2
use O2
Hypothesis: Going from Cenancestor to 3
Domains
II. Going from prokaryotes to eukaryotes
Cytoplasm
DNA
Plasma
membrane
How we got
organelles- the
hypothesis
Ancestral
prokaryote
Infolding of
plasma membrane
Endoplasmic
reticulum
Nucleus
Nuclear envelope
Engulfing
of aerobic
heterotrophic
prokaryote
Cell with nucleus
and endomembrane
system
Mitochondrion
Mitochondrion
Ancestral
heterotrophic
eukaryote
Engulfing of
photosynthetic
prokaryote in
some cells
Plastid
Ancestral
Photosynthetic
eukaryote
Hypothesis: Going from Cenancestor to 3
Domains
II. Going from prokaryotes to eukaryotes
•First, membrane in-folding created
endoplasmic reticulum and nucleus
Hypothesis: Going from Cenancestor to 3
Domains
II. Going from prokaryotes to eukaryotes
Endosymbiotic Theory
•second, endosymbiosis
led to formation of
mitochondria and
chloroplasts
mitochondria from
heterotrophic
(aerobic)
prokaryote
chloroplasts
from
photosynthetic
prokaryote
(Cyanobacteria
?)
Modern evidence for Endosymbiotic
Mitochondria and chloroplasts
Theory are prokaryotelike