Origin of life

The facts……. hidden somewhere
The story….….. unrevealed
The truth….. not known exactly
The path…. untraced
An attempt to explore the way!!!
ORIGIN
OF chemistry,
LIFE and
An effort
to blend biology,
physics in the search to identify and
understand the origin of life in the universe
It’s a “Journey

Back In Time”…

By Kalpana Stuti, Ritu, Gauri
Miranda House


ORIGIN OF LIFE


BIG BANG
Cosmic dust and gases+ H2O
Oceans
Haldane soup
Reducing atmosphere(gases like
CH4,NH3,N2,CO2,H2O responsible for
abiotic synthesis of organic compounds)

OPARIN-HALDANE THEORY
Haldane Soup

Simple Molecules

Complex Molecules (building blocks)

Aggregates (coacervates and microspheres)

Microsphere

Protocells( proprimitive stage before formation of true cell

Proto cells + nucleic acid = self replicating system

“CELL”


ENERGY YIELDING SYSTEM
•

“Cell”

• Chlorophyll

Energy Yielding System
development

Photosynthesis
O2 evolved

Ozone Formation (shielding effect)
• Atmosphere

• Evolution

changed to oxidizing from reducing.

of photosynthesis which is followed by
respiration.


CELL

Replication

Metabolism

Homeostasis

Anaerobes

Aerobes

Chemotrophs

Heterotrophs

Chemoheterotrophs
Prokaryotic Cells

Endosymbiotic Theory

Chemoautotrophs
Eukaryotic cell


How Eukaryotic Cell Changed to
Multicellular Organism….


EVIDENCES???
•

Geological Evidence

•

Precambrian Fossil Evidence

•

Laboratory Evidence


GEOLOGICAL EVIDENCE
•

Sedimentary rock in past 500 million years are silicate sands clay, quartz type
indicating oxidizing conditions.

•

Ancient Precambrian sediments containing sands with reduced iron minerals found in
Canada, Brazil, South Africa.

•

Banded iron ore deposits with mixed oxidation states in Quinland, Russia, India and
Australia


PRECAMBRIAN FOSSIL EVIDENCE
•

Elso Barghoorn et al studied polished thin sections of silica rich cherts from Gunflint
region of Northern Minnesota and Southern Canada with optical and electron
microscope.

•

Living organisms algae, fungi, microbes associated with banded iron ore cherts
indicates that they were probably laid down under reducing atmospheric conditions.


LABORATORY EVIDENCE
MILLER & UREY EXPERIMENT
•

of H4,NH3, H2, and water
•A mixture
was put into a flask and energized
by an electrical discharge apparatus
to represent ultraviolet radiation .
•The products were allowed to
condense and collect in a lower flask.
•. After a week, Miller and Urey
found a dark brown scum had
collected in the lower flask and was
found to contain several types of
amino acids together with sugars,
tars, and various other unidentified
organic chemicals.


How could polymer form in dilute aqueous
solution when polymerization is a
dehydration process?
•

Sidney Fox experiment – Fox found that dry amino acids heated to 160-210OC, forms polymers of

•

Cinder Cone Hypothesis - Protenoid material first polymerized on hot dry volcanic Cinder Cones

molecular weight 300,000 provided mixture contains Aspartic Acid and Glutamic Acid. Thermal
protenoids so formed, if washed with water, form microspheres of fairly uniform diameter of 20, 000Ao

and then it was leached into oceans by rains to form microspheres.

These became early segregated chemical systems and eventually led to protocells.


COACERVATES
•

They tend to concentrate some molecules in their
interior and this in an ability that most primitive
protocells would have acquired. Behavior of
Coacervate shows how earlier protocells would have
achieved internal compositions that were different
from their surroundings and could have developed
certain amount of chemical evidences.

Coacervate droplets formed
by interaction between
gelatin and gum arabic. A. I.
Oparin


Starch

Amylase
Amylase

Maltose

Sunlight

Chloroplast
e- + Dye
Ascorbic
Acid + Dye

Reduced Dye
(colour change)



PANSPERMIA THEORY
Organic compounds arrived from outer space
It states that hydrocarbons and other organic
molecules (molecules that organisms contain or that
might lead to the genesis of life) have been found in
meteorites –
 It means that at least prebiotic chemistry that leads
to the primordial soup might be going on there.


Evidences in support of this theory
•

In 1969, a meteorite landed in Australia that was 12% water and contained traces of 92
amino acids.
Inference- It points to not only the presence of organic compounds in outer space, but
also the capacity of such compounds to reach earth.

•

Fred Hoyle and Chandra Wickramasinghe have argued persistently since the 1970s that
complex organic substances, and perhaps even primitive organisms, might have evolved
on the surface of comic dust grains in space and then been transported to the Earth's
surface by comets and meteorites.


Where did life begin???
•

There is an ongoing debate regarding the most probable site of life's origins.

•

The prevailing paradigm - life began near the ocean's surface, bathed in sunlight.

•

Current Research - life arose near deep hydrothermal vents which is still under investigation.

"Scientists have long suspected that life on Earth originated in the ocean and strong evidence now suggests that the
earliest life on our planet occurred in the depths
the ocean
in the
absence of heat and light."
Millerof and
Urey
found
-- Pulse of the Planet, American Museum of Natural History

Photograph from National Geographic magazine


Deep-sea Vents
•
•

Their discovery in late 1970’s stretched our concept of the origin of life on earth.

•

It raised the possibility that earlier vents supplied the energy and chemical precursors

Can life exist and that too thousands of meters beneath the surface of sea in absence of
sunlight?
for origin of protobionts.


Exploring the deep ocean floor
View of the first hightemperature vent
(380°C) ever seen by
scientists during a dive
of the deep-sea
submersible Alvin in
1979.
Such geothermal vents
are called smokers.
This photograph shows a black smoker, but
smokers can also be white, grey, or clear
depending on the material being ejected.

Photograph by Dudley Foster from RISE
expedition


Vent Community

A vent community in its prime: Pale pink eelpout fish and white
brachyuran crabs swim and scuttle among blood-red tube worms
large and small. Scientists are still trying to figure out how the
offspring of such organisms disperse over long stretches of
inhospitable seafloor to colonize widely separated vent systems.


Giant Clams

The size of deep-sea giant clams is evident from the
hands of a scientist holding them.
(Photograph by William R. Normark, USGS.)


Giant Tube Worms: RIFTIA
•

On the bottom of the ocean
around deep-sea hydrothermal
vents, there is a profusion of life
that thrives on the hydrogen
sulfide (H S) gas released from
2
the vents.and live inside hard,

shell-like protective tubes that
attach to the rocks.

Giant tubeworms that live around hydrothermal vents
on the sea floor. These creatures are about the size of
your hand in shallower waters, but in the ocean's deep
they have been found as big as eight feet long!