Download Origin of Life

Origin of Life
• When did life begin?
• What did the earliest life look like?
• How did life emerge from non
non--living
materials?
• Will life ever originate again?
Are we extra
extra--terrestrials?
• A meteorite
t it from
f
Mars
M
was
split to reveal what looks like
fossil bacteria.
• This finding suggests life
existed on Mars at some point
The Boeing
g 747 Argument
g
The probability of life originating on
earth is no greater than the chance of
a hurricane, sweeping through a
scrapyard, would have the luck to
assemble a Boeing 747.
Sir Frederick Hoyle
However statistically improbable the
entity you seek to explain by invoking
a designer, the designer himself has
got to be at least as improbable. God
is the Ultimate Boeing 747.
Richard Dawkins
Earliest
Fossils
Fossil microbes from South Africa (3.5 billion years old)
Dating
g Rocks with Radioisotopes
p
R di ti
Radiation
Potassium (K40) gradually
decays into Argon (Ar40)
H lf lif = 1
Half-life
1.2
2 billi
billion years
Igneous rocks can be dated
accurately
t l because
b
argon
cannot escape this rock.
Living stromatolites
Essential Properties of Life
Life must have the ability to evolve by
natural selection
selection.
• Metabolism
• Reproduction
• Heritability
[Source: Lusisi et al. 2006, Naturwissenschaften 93: 11-13]
All forms of life
(
(recognized
i db
by
humans) have a
genotype and a
phenotype.
genotype
phenotype
h
t
The Chicken or the Egg?
• There is a catch
catch--22 in the origin of life
• RNA/DNA (the genotype) codes for
proteins (the phenotype) and proteins
replicate this code.
• Which came first? RNA? Proteins? Or did
they evolve at the same time?
Maybe
y the chicken
was also an egg.
• RNA has both genotypic and
phenotypic functions (i.e.,
RNA can start
t t reactions).
ti
)
• Some hypothesize that RNA
was the first form of life.
• This theory assumes RNA
was capable of selfself-replication
The Origin of Genetic Complexity
[Source: Wolf & Koonin 2007 Biology Direct 2: 14]
Under what conditions did life arise?
The MillerMiller-Ureyy Experiment
p
electrode
condenser
water +
organics
2 CH4 + NH3 + 2 H2O → 5 H2 + C2H5O2N
methane
ammonia
water
hydrogen
glycine
Miller & Urey’s
Urey s Theory:
Great Hope or Great Disappointment?
• 10 amino acids used in
proteins and 12 not used
in proteins
• Simple
Si l sugars ((unstable)
t bl )
• Certain nucleic acids
Will we eventually create life? Scientists says “yes
“yes.””
Three major
j hurdles to creating
g
synthetic life:
1) A container,
container or membrane,
membrane for
the cell to keep bad molecules out
and allow good ones in,
2) A genetic system that controls
the functions of the cell,, enabling
g it
to reproduce and mutate.
3) A metabolism that extracts raw
materials from the environment.
Synthetic Life
[Source: Lusisi et al. 2006 Naturwissenschaften 93: 11-13]
Some scientists are “cheating” to make new forms of life
life.
Craig Venter,
Co explorer of
Co-explorer
The Human Genome