The document discusses several key stages in the origin of life on Earth: 1) Abiotic synthesis of organic molecules like amino acids from simple gases in Earth's early reducing atmosphere, as demonstrated by the Miller-Urey experiment. 2) Self-assembly of these organic molecules into increasingly complex structures like microspheres and coacervates. 3) Emergence of primitive self-replicating systems able to direct their own metabolism. 4) Development of the first genetic code in these precellular systems linking nucleic acids to protein synthesis. 5) Evolution of fully formed cells enclosing genetic material within a nuclear membrane.

1. The Big Bang theory of the
formation of the universe
• All material in the universe was created in
a huge "explosion," creating and defining
matter and space.
• The sudden cooling of the superheated
ejecta facilitated the combination of
atomic components into atoms and
molecules.
• These clouds of gasses eventually cooled
and formed the principle components of
galaxies - including stars and planets.

2. Formation of the solar system
A. The earth formed approximately 4.6
BYA (billion years ago.) Initially,
there was a cloud of gasses and
dust particles, possibly originating
from the ejected particles of a
nearby supernova.
B. The cloud gradually contracted and
flattened, concentrating about 99%
of its mass in the center with the
rest rotating counterclockwise in a
flattened disk.
C. As the disk rotated, turbulence was
created, causing condensation of
the disk into small, turbular eddies.
These gradually accreted together
to form protoplanets.
D. These protoplanets further accreted,
creating the mature planets of the
solar system.

3. Origin of life
Oparin-Haldane hypothesis.
• The atmosphere of the early Earth may have been chemically reducing in nature,
composed primarily of
1. methane (CH4),
2. ammonia (NH3),
3. water (H2O),
4. hydrogen sulfide (H2S),
5. carbon dioxide (CO2) or
6. carbon monoxide (CO), and
7. phosphate (PO43-), with
8. molecular oxygen (O2) and
9. ozone (O3) either rare or absent.
• In such a reducing atmosphere, electrical activity can catalyze the creation of
certain basic small molecules (monomers) of life, such as amino acids.
• This was demonstrated in the Miller–Urey experiment by Stanley L. Miller and
Harold C. Urey in 1953.
• Phospholipids (of an appropriate length) can spontaneously form lipid bilayers, a
basic component of the cell membrane
• These organics, accumulated in the surface waters of the ocean, forming a
"primordial soup", out of which, in time, life in its most elementary form emerged.

4. Oparin-Haldane model
The steps of the Oparin-Haldane model are described
below.
• 1) Organic molecules including amino acids and
nucleotides are synthesized abiotically (without living
cells).
• 2) Organic building blocks in the prebiotic soup are
assembled into polymers of proteins and nucleic
acids.
• 3) Biological polymers are assembled into a self-
replicating organism that fed on the existing organic
molecules.

5. Miller-Urey Experiment
• Miller-Urey apparatus Conducted in 1953 by
Stanley Miller under the supervision of
Harold Urey; the first experiment to test the
Oparin-Haldane theory about the evolution
of prebiotic chemicals and the origin of life
on Earth.
1. A mixture of methane, ammonia, hydrogen,
and water vapor, to simulate the version of
Earth's primitive, reducing atmosphere
proposed by Oparin, was introduced into a
5-liter flask and energized by an electrical
discharge apparatus to represent ultraviolet
radiation from the Sun.
2. The products were allowed to condense and
collect in a lower flask which modeled a
body of water on the Earth's surface.
3. Heat supplied to this flask recycled the
water vapor just as water evaporates from
lakes and seas, before moving into the
atmosphere and condensing again as rain.

6. Miller-Urey Experiment
• After a day of continuous operation, Miller and
Urey found a thin layer of hydrocarbons on the
surface of the water.
• After about a week of operation, a dark brown
scum had collected in the lower flask and was
found to contain several types of amino acids,
including glycine and alanine, together with sugars,
tars, and various other unidentified organic
chemicals
• The conditions were:
1. A gaseous phase containing reduced sources of
carbon (methane), nitrogen (ammonia), oxygen
atoms (water), and hydrogen atoms from any or all
of these precursors as well as hydrogen gas.
2. Electrical energy provided by spark discharge.
3. Ambient temperature between 0 and 100 C.
4. Sterile conditions to begin with (abiotic
environment).
• Apparatus used in the Miller-
Urey experiment

7. Microspheres
• Microscopic, firm spherules which form on the cooling of hot
saturated solutions of proteinoids.
• First reported in 1959 by Sidney Fox, K. Harada, and J.
Kendrick - proposed that microspheres might represent a
significant early stage in precellular evolution.
• It has greater stability than coacervates.
• ranging from 1.4 to about 2.5 microns in diameter.
• Retain their form for several weeks and, when sectioned, may
display a double-walled structure.
• Fox argued that microspheres also display characteristics of
primitive nerve cells.

8. Coacervates
• Name derives from the Latin coacervare, meaning to
assemble together or cluster
• Measure 1 to 100 micrometers, possess osmotic properties,
and form spontaneously from certain weak organic solutions
• A spherical aggregation of lipid molecules making up a
colloidal inclusion which is held together by hydrophobic
forces.
• Suggested by Oparin that coacervates may have played a
significant role in the evolution of cells.
• If the droplets which form contain a colloid rich in organic
compounds and are surrounded by a tight skin of water
molecules then they are known as coacervates.
• First investigated by Bungenburg de Jong in 1932.

9. Origin of life
• Stage 1: The formation of the earth and atmosphere is considered the first
stage in the long trek from inanimate matter to life.
• This stage provided the inorganic raw materials for the evolution of life and
set up the conditions for their interaction.
• Stage 2: Abiotic synthesis of organic molecules (Amino acids and
nucleotides): The second stage produced organic molecules through
interactions between inorganic substances, driven by energy sources such
as lightning and ultraviolet radiation from the sun.

10. Origin of life
• Stage 3: In the third stage, the organic molecules
present assembled randomly into collections
capable of chemical interaction with the
environment.
• As the collections formed, interactions taking place
within them produced still more complex organic
substances, including polypeptides and nucleic
acids.
• Some of these collections of molecules were
capable of carrying out primitive living reactions.
• There is little agreement on the form taken by the
first spark of life in these primitive aggregates.

11. Origin of life
• Stage 4: In the fourth stage, a genetic code appeared in the
primitive living aggregates.
• This code regulated duplication of information required for
reproduction of the aggregates and established the link
between nucleic acids and the ordered synthesis of proteins.
• Things were still pre-cellular, but with these developments
(directed synthesis and reproduction), life was fully
established in the molecular assemblages.

12. Origin of life
• Stage 5: The fifth and final stage involves conversion of the
pre-cellular assemblages into fully organized cells with a
nuclear region and a cytoplasm, all enclosed by an outer
boundary membrane--a plasma membrane.