of Origin Life (overview)
An overview of the logic of the origin of life
Where did the earth of Earth/what is the history
of lifes origins?
How is it possible that life could form?
Why doesnt life arise de novo today?
Fossilization
How do fossils form?
What can go wrong?
How do we date them?
An overview of the diversity of life
Problems with the the Five-Kingdom system
The three-domained universal tree
The n-Kingdom system of organismal
classification
Singularity: Pre-Big Bang
Inflation: Energization of Big Bang
Universal expansion: Energy provided by Inflation
Sub-atomic particles: Energy
as universe cooled
Mass conversion
Atoms: mostly Hydrogen
Gas-cloud inhomogeneities: provided gravity wells
Stars: gas-cloud gravitational collapse
Super novae: forgers & disseminators of metals
Metals: Atoms other than H and He
Molecules: More complex than H2
Accretion: Formation of planets
Planets: gravity wells (like stars but smaller)
Planets: solid substrate upon which life can evolve
Chemical evolution: Formation of more-complex
chemicals, in space or on planets
Replicators: Chemicals capable of templating their
own replicaiton
Separate phenotype: Molecules responsible for some
phenotype are other than those carrying genotype
Individuality: Protocells then cells (more complex
phenotypes can evolve if not shared between replictors)
Prokaryotes: Earliest true cells (~3.5 bya)
Endomembrane system: Increase in cellular
morphological complexity
eukaryotes
Endosymbiosis: Further increase in eukaryote
complex and expansion of biochemistry
Multicellularity: Cooperative grouping of differentiated
cells
Etc.: Plants, Fungi, Animals
Logic of Origin of Life
Origin of Life (overview)
Origin of Earth (overview)
Chapter 26:
The Tree of Life:
An Introduction to
Biological Diversity
We will concentrate in this lecture on three
things:
Large volumes
quantitatively lots of (large
numbers of) experiments
Diverse environment
qualitatively lots of (high
diversity of) experiments
Lots of Time
perhaps hundreds of millions of
years
Diverse, numerous experiments plus potential for
experiments to build upon each other (evolution)
Not-oxidizing atmosphere
without lots of O2
around, organic molecules are much more stable
This was the case before modern photosynthetic
organisms evolved (i.e., cyanobacteria)
Organic molecule stability without O2 allowed life
to evolve slowly from nonliving material
Organic Molecules
presence of complex
organic molecules can be inferred but also can be
addressed experimentally (e.g., Miller-Urey Exp.)
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Someday we will even understand the chemistry
No Competition:
Unlike today, there were no super-sophisticated
modern organisms to compete with (i.e., no
bacteria)
In the land of the blind the one-eyed chemical is
king!
Know
names and
dates of
Eons and
Eras (not
Periods or
Epochs)
Solar radiation supplies energy
that help to modify extraterrestrial
organic compounds, such as in
comets, into complex forms, which
then can fall to Earth
Major Events in Evolution
Chemicals that are stable and can duplicate
themselves naturally increase in abundance
Miller & Urey Experiment (1953)
Logic of self replication & natural selection:
Stuff that is durable and easily made tends to
accumulate
Terrestrial Energy Sources
Logic of Origin of Life
Geological Time
Extraterrestrial Energy Sources
Energy
volcanoes, deep-sea vents, lightning,
sun light (including lots of UV pre-ozone layer
since ozone comes O2), chemicals from space
Know
relative
order of
occurrence
of indicted
phenoma
rather than
absolute
timing
Model for
Abiotic
formation
of amino
acids, etc.
Lightning and
volcanoes are
sources of higher
energy (e.g., heat)
found at the Earths
surface and in the
atmosphere
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Modern Vents
mineral-laden
superheated water
S0 (rain)
HS
HS
sulfur compounds (electron donor)
e-
FeS
FeS
sulfur-oxidizing bacteria
O2 (electron acceptor)
H2 (electron donor)
e-
chimney
methanogenic archaeans
CO2 (electron acceptor)
Chemical Evolution: RNA
additional
time
Protophenotype
on top of
genotype
Chemical
evolution
Shown is abiotic
genotype (heredity)
With self replication the mere
presence of a substance
biases the environment toward
having more of that substance
Laboratory Protobionts
Shown is some degree abiotic individuality
Selection will be for rapidity
of formation, slowness of
decomposition, minimization
of errors during formation,
and, eventually, for
phenotype that augments
these properties
A catalytic RNA
(this one acts as an
RNA polymerase)
Ribozymes
Terrestrial Sources
Chem. Energy Evol. through True Cells
Heating of
seeping sea
water by
Earths
mantle frees
reduced
minerals
that become
available to
bacteria at
oceanic
geothermal
vents
(underwater
geysers and
hot springs)
Catalytic
RNA has
both
genotype
and
phenotype
As a nucleic acid,
RNA is an obvious
precursor to DNA
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Paleontology & Fossils
Fossils
Paleontology is
the study of the
biology of the
past
Fossilization
Fossilization: What can go wrong
Protocells (Individuality, sort of)
Paleontology
Protocells have heredity and individuality
(keeping ones phenotype to ones self)
Fossils are preserved remnants of
the morphology, context, and, to
some degree, the molecules of
dead organisms
Start with dead organism
Loss of organism parts due to scavenging,
predation, rotting; typically at best only hard
parts remain for reasonable duration
Protect organism from air, e.g., by burying in
sediments, by volcanic ash, in peat bogs, in tar
pits, in tree sap
Organisms that live in forests tend not to
fossilize due to a lack of burying mechanisms
Old strata that is being built up over time will
retain fossils; have to have rock to have fossils
Melting, twisting, bending, etc. of rock is not
good for fossil preservation
Lack of erosion prior to mineralization
Lack of geological distortion
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Once a fossil is no longer buried, it deteriorates
rapidly and likely will be known to science only if
discovered by a trained individual during a brief
period before its loss
Discovery by trained person
Conclusion 1: Things with hard parts, that live
in environments in which burying soon after
death is likely, and are represented by large,
long-lived populations will likely fossilize
Dating Fossils
Presumably the vast majority of fossils have not
yet been unburied
Conclusion 2: Things with no hard parts, that
live in environments in which burying soon after
death is unlikely, and are represented by small,
short-lived populations will likely not fossilize
Some Geology
Relative Dating
In order to understand paleontology, it is
important to have a good record of past life
forms, and to have a good understanding of
when those organisms had been alive
That way one can trace morphological changes,
and thereby evolutionary relationships, over
time
Relative vs. Absolute Dating
Relative dating:
Geological time scales
Relative position in strata
Index fossils
Absolute dating:
Actual clock
E.g., radioactive decay
Clock must be started
Other Indexes
Index Fossils
Fossilization: What can go wrong
Reexposure to air
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Geological Time &
Mass Extinctions
Starting K-Ar Clock
Potassium-Argon Dating
Radiocarbon Dating
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Absolute Dating = Clocks
Relative Dating &
Geological Time
Prokaryotes, the 1st Cells
Early-Cells Evidence: Cyanobacteria
Early-Cells: Stromatolites
Mass Extinctions
K-T Boundary: Chicxulub Impact
Modern Stromatolites
3.5 billion years old = age of
oldest prokaryote fossils
Key to stromatolite
formation is an
absence of animalassociated mixing of
sediments (e.g., the
equivalent of not letting
your little brother into
your room)
Modern Leptolyngbya
Stromatolites are still
formed today at a few
places like Shark Bay in
Australia
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O2
Banded iron formations
are evidence of the
impact of increasing
atmospheric oxygen
densities on soluble
iron found in sea water:
oxidation created
insoluble form, a.k.a.,
rust
Endosymbiosis = Eukaryotes
Serial Endosymbiosis
Ever More Symbiosis
Cyanobacteria =
Fossil Stromatolites
Banded Iron Formations
The remarkable protist Mixotricha
paradoxa, which lives in the gut of
termites, has three types of bacteria
attached to its surface that provide it with
motility. A fourth type of bacterium lives
inside Mixotricha and digests wood
fragments eaten by the termite. p. 525,
Campbell & Reece (2005)
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Origins of Animal Phyla
Colonial before Multicelluar
Multicellular Hetrotrophs
Fossil animal
embryos
Classifying Life 5 Kingdoms
Colonies then More!
Multicellularity
The difference between
colonial organisms and
multicellular organisms
has to do with the
degree of differentiation
among the cells: in
multicellular organisms
different cells have
different tasks, and
those cells are more
dependent upon each
other
Note bias
toward
large
things!
Prokaryotes
Non-plant,
fungi, or
animal
eukaryotes
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n-Kingdom System (2/2)
n-Kingdoms System(s)
The universal ancestor
had DNA, codons, RNA,
proteins, etc.
n-Kingdom System (1/2)
Three Cellular Domains
5 Kingdom System
16S rRNA
Link to Next Presentation
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