Transcript history of life

CHAPTER 17
HISTORY
OF LIFE
1920s A. I. Oparin, of Russia, and J. B. S.
Haldane of Great Britain
“Primordial Soup”
What is Primordial Soup?
Chemical and physical processes in Earth’s primordial
environment eventually produced simple cells.
1. Monomers
What is needed? 2. Polymers
3. Replicating Molecules
4. Protobionts
No?
H2O
2
N2
3
Early
Earth
4
1
5
REACTANTS
Abiotic Synthesis
PRODUCTS
#1
Organic
Molecules
(amino acids)
“Monomers”
#2
monomers  polymers
#3
Self Replicating Molecules
Many researchers now favor the hypothesis that the first hereditary material was not DNA, but RNA,
which may also have functioned as the first enzymes.
(This helps resolve the "chicken and egg" paradox of which came first, genes or enzymes.)
According to this hypothesis, the molecular biology of today was preceded by an "RNA world."
#4
the packaging of all these molecules into "proteinoid microspheres,"
droplets with membranes that maintained an internal chemistry different
from the surroundings.
Living cells may have been preceded by protobionts, aggregates of abiotically produced molecules.
Protobionts are not capable of precise reproduction, but they maintain an internal chemical
environment different from their surroundings and exhibit some of the properties associated with
life, including metabolism and excitability.
Sidney Fox
Droplets called liposomes form when the organic
ingredients include certain lipids
selectively permeable
Liposomes behave dynamically, sometimes growing by engulfing smaller liposomes and then
splitting, other times "giving birth" to smaller liposomes
If enzymes are included among the ingredients, they are incorporated into the droplets.
The protobionts are then able to absorb substrates from their surroundings and release the products
of the reactions catalyzed by the enzymes.
Reproduction
Metabolism
Hydrothermal Vents
“Panspermia”
Comet/Meteorite
PROGRESSION OF LIFE
Geologic Time Scale
Major episodes that shaped life as a phylogenic tree
LIFE:
Diversified into different types of cells by
3.5 billion years ago
Australopithecines
Homo habilis
Homo erectus
Homo sapiens
Upright 
Larger Brain
Humans diverged 5 million years ago
Genus “Homo”
Homo
sapiens
10 mile diameter
“Cambrian Explosion”
Extinctions
“Dinosaurs”
Meteorite = 50 meter
20,000 years ago
Manicougan Reservoir
Quebec Canada
200 Million Years ago
Tunguska Siberia
1908
Uninhabited Area
Wolfe Creek Australia
2003
Illinois
EXTRATERRESTRIAL
LIFE?
What is needed?
Plateau
 Size of Grand Canyon
Sea
MICROBES?
1996
Europa (Jupiter)
2010
726 Extrasolar Planets
Kepler -22b
~600 light years away
"It's 2.4 times the size of the Earth, it's in an orbital
period (or year) of 290 days, a little bit shorter than the
Earth's, it's a little bit closer to its star than Earth is to
the sun, 15 percent closer.
"But the star is a little bit dimmer, it's a little bit lower in
temperature, a little bit smaller. That means that planet,
Kepler-22b, has a rather similar temperature to that of
the Earth...If the greenhouse warming were similar on
this planet, its surface temperature would be something
like 72 Fahrenheit, a very pleasant temperature here on
INTELLIGENT LIFE?
Drake Equation
10,000 Intelligent Civilizations in
the Milky Way
Where?
What about “next door”?
In the universe, there are 1020 (100,000,000,000,000,000,000) stars that resemble our Sun
(in just our own galaxy, the Milky Way, there are 400 billion stars or 400,000,000,000 stars)
At least 10% of these suns have planets around them (1019, or 10,000,000,000,000,000,000).
That's a lot of planets.
If only a small fraction of these planets - say 1 in every 10,000 (0.01%)- of the right size and
distance from its star existed to duplicate the conditions in which life is hypothesized to have
originated on Earth, the "life experiment" may have been repeated 1015 times
(1,000,000,000,000,000) - or a million billion times
In addition, life may have originated and evolved differently on other planets - using molecules
other than carbon (like silicon, which has an atomic structure similar to carbon)