 Abstract
This is the report on the comparative study of origin of life. How life originated and what are
the evidences to prove them? The answers to these questions are discussed along with
different theories proposed by different scientists and finally a comparative study is done in
this research.
 Introduction
Man has always been perplexed about the origin of life on earth. For centuries, number of
theories and hypothesis have been suggested to explain the origin of life in their own way.
Earlier life was thought to be created by some supernatural force in a very short time. Most
of the religions and civilizations still believe it to the supernatural phenomenon of the past.
By the traditional Judaeo-Christian account of creation, the whole world and all the species
were created in the just six days. Some of the theories being discussed here are:
1. Spontaneous Generation Theory
2. Chemical Evolution of life (Scientific hypothesis)
3. Cosmozoan theory (Life from other planets)
4. Other Theories
 Literature review
Different research and experiments had been since a very long time. Scientists have been
studying about origin of life from ancient time.Scientists like Darwin ,Paouster,Miller and
Urey, Oparin and Haldane, Aristotle, Jehovah, Szostak etc have studied and researched in
this subject,
 Rationale of the study
Actually this study is done because we were interested in this matter i.e. origin of life. We
wanted to know more about this and extend our knowledge. Also we got this topic for the
study so we have done this research.
 Objective
The major objective of the research is to study about the origin of life comparatively, collect
related datas and gain maximum knowledge related to different theories and experiments
done by different scientists.
 Materials and methods
For the completion of this study, research or report ,different materials and methods were
applied. Almost all of them were the secondary sources. Internet surfing, different books,
magazines, newspaper, library and aid of several teachers and friends are some the materials
and method of our research.
 Results
At first different theories of no scientific evidences were proposed that were discarded.Some
of them are theory of special creation, Anaximenes (582-524 B.C.) concept, Anaximander
(611-547 B.C) Idea, Empedocles (495-435 B.C.) philosophy,cosmozoan theory and even
spontaneous generation of life.
Later Oparin- Haldene theory of Biochemical origin of life was proposed which to some
extent was more scientific. This theory explained the origin of life along with the origin and
and evolution of earth and its atmosphere. The primitive atmosphere of earth had water,
methane, ammonia and cynamide that underwent series of reactions and as a result, mixture
of biologically important macromolecules like proteins ,sugars, nucleic acids etc. were
formed.
This theory was experimentally checked my Miller and Urey, later on.
The result of Miller and Urey’s experiment suggested that electric discharges produced
during lightning in the primitive atmosphere of earth containing ammonia , hydrogen and
methane, water vapour might have resulted in the formation of amino acids ,nucleic acids and
other organic compounds. It provides ample evidence in favour of biochemical origin of life
as explained by Oparin and Haldane.
Thus,this theory and experiment is more scientifically proven and evidented, we are
following the same till now.
 Discussion
Man has always been perplexed about the origin of life on earth. For centuries, number of
theories and hypothesis have been suggested to explain the origin of life in their own
way.
Different theories of origin of life are discussed below in brief:
Theory of special creation:
This theory was proposed by spiritual people. According to this ,all the plants and animals
were created by some supernatural power of god.
According to Bible, god created universe, plants, animals and men in seven days. The first
man was Adam and woman was Eve.
According to Hindu mythology, god Brahma created various forms of life as such in one
stroke.
As these theories have no any scientific evidences, these theories are not accepted.
Anaximenes (582-524 B.C.) concept:
He thought air to be the source of life. Idea of abiogenesis was also introduced by him
describing that animals and plants arose from a primordial terrestrial slime being energized
by the sun’s heat into life.
Anaximander (611-547 B.C) Idea:
He gave the idea that evolution of organism was taken from the formless form. He further
said that aquatic species were transformed into terrestrial species.
Empedocles (495-435 B.C.) philosophy:
He is called the father of evolution idea .He gave these four ideas in his philosophy.
-Life evolved gradually believing in abiogenesis.
-Plant life came first then animal life developed later.
-Imperfect forms were gradually replaced by perfect forms.
-Perfect forms were produced naturally due to extinction of imperfect forms.
Cosmozoan theory
This theory states that life came on earth from other planets or heavenly body.
It seems probable because all the events that occurred on earth might have occurred on other
planets as there are more than 1019 stars in this universe and Sun is one of them and earth is
just a small part of it.
As this theory has no much logic, it is discarded.
Spontaneous generation of life:
Ancient Chinese , Egyptians and Greeks believed in spontaneous generation of life. In fourth
century B.C., Greek philosopher, Aristotle believed that life could come into existence
spontaneously from non living material. People thought that snakes, frog, and fish arose from
mud, rats from garbage, Insects from plant juices and microorganisms from water and air.
This theory was well accepted for hundred of years. Many scientists tried different
experiments but the result remained unconclusive.
Van Helmont’s experiment:
In 17th century Van Helmont performed an experiment by keeping a dirty shirt with a few
wheat grains in a darkcupboard for 21 days. At the end of the experiment, mice were seen in
the cupboard and so he supported the theory by spontaneous generation.
Redi’s experiment:
Later in 1688, Redi, an Italian scientist tried to test this theory of spontaneous generation. He
kept dead fish, snake and meat in 4 wide mouthed flasks and left them open. He put the same
things in another set of 4 jars but sealed them.
Redi observed little white worms and larvae on decayed flesh in the opened flasks but didn’t
find any worms or flies in the sealed flasks.
Pasteur’s experiment:
In 1862 Louis Pasteur, a French microbiologist finally disapproved the theory of
spontaneous generation and gave the scientific explanation that life originates only from pre
–existing life. He performed the experiment with swan naked flasks. Pasteur was convinced
that microorganisms existed in the air and that non living matter like liquid is easily
contaminated by these. He tried to prove it by carefully sterilizing the solutions and showing
that no organisms grew in the sterilized solutions.
These theories went against the theory of abiogenesis and hence these theories were
discarded.
Scientific Hypothesis-Chemical Evolution of Life:
The chemical evolution of life is the most widely accepted scientific theory of origin of life.
It is based on the fact that the atmosphere of the earth was not the same what we see today
and earth is about 4600 million years old and life originated approx. 3600 years ago.
Origin of Earth:
Of the various theories suggested and from the evidences available, the earth is estimated to
be 4600 million years old. The earth had a different atmosphere from the one that exists
today. It has undergone no. of changes some of which are listed below:
-Sun and planets were formed together from a spherical cloud of gases and cosmic dust
which by rotation and gravitation developed sun at middle and a whirling belt of gases
around it.
-With time the clouds condensed by gravity and formed planets.
-At first earth was a somewhat in gaseous form later in molten state and finally after billions
of years earth is this.
-One of the major gases was water vapour which on cooling resulted in rainstorms that made
the earth’s oceans ,rivers and lakes.
-Earth’s atmosphere was mainly formed by gases like hydrogen, nitrogen ,water vapour and
carbondioxide.
-Free oxygen was not found at that time.
Oparin –Haldane theory (Biochemical origin of life):
Two biochemists , the Russian A.I. Oparin in 1923 and the Englishman J.B.S. Haldane 1928
independently gave the biochemical theory of origin of life.
According to Oparin- Haldane theory the complex organic molecules would have been
formed through a series of chemical reactions in the earth’s primordial soup or we might say
Darwin’s warm little pond.
-They proposed that the chemical synthesis of organic compounds occurred in the warm
premevial oceans.
-The energy for the synthesis of these chemicals was in abundance on earth. It was present in
the following forms:
I.
II.
III.
IV.
Powerful ultra violet radiations from from sun since there was no ozone layer to
inhibit this energy to enter the earth.
Heat energy from volcanoes.
Radiations from radioactive rocks.
Electric energy form lightning.
-Various organic molecules like amino acids, sugars and nucleotides bases were formed
spontaneously from ammonia , methane and water.
-Continuous rains washed these compounds into oceans and ponds.
-Since, there were no living organisms to consume them and no oxygen to destroy
intermediate compounds, the organic compounds necessary for life gradually accumulated in
the oceans which became primordial soups which could support life.
-Complex organic molecules were formed through chemical reactions in these nutrient rich
primordial soups in which life could have arisen.
-Oparin suggested the formation of clusters or specialized droplets which could grow, divide
and replicate themselves.
This theory explained the origin of life along with the origin and and evolution of earth and
its atmosphere. The primitive atmosphere of earth had water, methane, ammonia and
cynamide that underwent series of reactions and as a result, mixture of biologically important
macromolecules like proteins ,sugars, nucleic acids etc. were formed.
Synthesis of simple organic molecules:
Elements like carbon, hydrogen, nitrogen , oxygen were most abundant on the primitive
earth in the beginning. These elements existed in the gaseous state due to high temperature.
As the surface gradually cooled, these elements combined each other to form water, methane
, ammonia and cynamide. These molecules were considered as the key molecules in the event
of origin of life on earth.
Due to condensation, polymerization, oxidation, and reduction of the simple molecules,
complex molecules such as simple sugar, amino-acids, fatty acids etc were formed.
Above molecules again reacted and aggregated together in hot water of ocean and formed
new molecules like purines, pyrimidines and nucleotides.
Synthesis or formation of nucleic acids:
It is presumed that the sugar, phosphate,, purines and pyrimidine combined together to form
nucleotides. A larger number of such nucleotides were combined to form nucleic acids such
as DNA and RNA. The formation of DNA and RNA was the significant event in the
formation of life in the earth. Since nucleic acids were capable of self –duplication or
multiplication .Hence, these were considered as the first sign of origin of life.
Miller and Urey’s Experiment:
Stanley Miller and Harold C. Urey had a series of experiments and put Oparin- Haldane
theory to test in 1953.They tried to recreate the conditions that might have existed on earth in
the laboratory. They set up the apparatus as given in the figure. They first evacuated the
apparatus , made it sterile and then introduced a mixture of gases including methane,
ammonia, and hydrogen into it. There was no free oxygen.
-Water in the flask was boiled to promote circulation and to provide necessary water vapour
for reaction.
-Energy was supplied by the electric sparks from electrodes in the gaseous chamber.
-At one place a trap was provided to collect the products of the chemical reaction during the
run.
-The experiment was run continuously for about a week and then the products formed were
analysed.
Result of the experiment:
The chemicals formed during the experiment included amino acids like alanine, glycine,
aspartic acid, aldehydes, simple sugars like ribose etc.
Fig: Apparatus set up by Miller and Urey to recreate conditions of primitive atmosphere
(The conditions created were of gases , heat, rain, electric discharge like lightning as
supposed to have existed on earth.)
Conclusions of the experiment:
The result of above experiment suggested that electric discharges produced during lightning
in the primitive atmosphere of earth containing ammonia , hydrogen and methane, water
vapour might have resulted in the formation of amino acids and other organic compounds. It
provides ample evidence in favour of biochemical origin of life as explained by Oparin and
Haldane.
 Conclusion
In this way ,our group was able to prepare a report on ‘the comparative study of origin of
life’ and also were able to gather maximum knowledge in this topic.
 Acknowledgement
We group members would like to express our warm appreciations to the management
committee. We would also like to thank the organizers for organizing such a programme and
for giving this task to learn more and extend our knowledge in the concerned topic and also
like to appreciate Mr. Dipen Dahal (Program director ) and KP Sir (Zoology).We are grateful
to library madam, lab assistants and also Pramit Raj Sharma , Bipindra Pandey, Shyam
Khadka and Jaya Prakash Shrestha.
 References
i.
ii.
iii.
iv.
v.
vi.
vii.
http://runonce.msn.com/runonce3.aspx
http://rogerwendell.com/images/evolution/dmns_origin_of_life_09-02-2006.jpg
http://www.cyberessays.com/lists/origin-of-literature/page1470.html
http://books.google.com.np/books?id=Jv8psJCtI0g
http://en.wikipedia.org/wiki/File:Stromatolites.jpg
A text book of HS Biology-A.K. Keshari-EKTA
Modern Graded Science-XI
 Annexes
Darwin
Oparin and Haldane