- 1 Chemosynthetic Theory of Origin of Life – The Origin of the Universe, Earth, and Life
- 1.1 A. Experiment of Francesco Redi
- 1.2 B. Experiment of Spallanzani
- 1.3 C. Experiment carried out by Louis Pasteur
- 1.4 Time of Origin of Life
- 1.5 The Atmosphere on Earth when the First Life Arose
- 1.6 Evidence in Favour of Chemosynthetic Theory
- 1.7 Several Reactions Leading to the Formation of Biomolecules
- 1.8 Conditions that Sparked Life on Earth
- 1.9 Origin of Life Form
- 1.10 Possible Steps in the Origin of Life Forms
The Biology Topics of biotechnology involve using living organisms to develop new products or solve problems.
Chemosynthetic Theory of Origin of Life – The Origin of the Universe, Earth, and Life
A. Experiment of Francesco Redi
Francesco Redi in 1668 designed one scientific experiment to test spontaneous creation. In two different jars pieces of fresh meat were kept. After that one jar was kept open and the other jar was covered with a piece of cloth. After a few days in the open jar maggots developed. On the other, the covered jar did not develop any maggots. From this observation, Redi could be able to prove that in the open jar flies from the exterior laid eggs on the meat, and maggots developed from the eggs. On the other hand, flies could not reach the pieces of meat inside the covered jar and therefore, no maggot could develop within the covered jar. This experiment then disproved the spontaneous generation of life.
B. Experiment of Spallanzani
On the basis of Redi’s experimental data, Lazzaro Spallanzani designed an experiment to see whether spontaneous generation of life is possible. In his experiment, he kept boiled broth in two separate bottles. Then he sealed the open mouth of one bottle and the other bottle was kept open. After a few days in the open bottle sign of life could be noticed. This experimental observation supported the idea of Redi against the spontaneous generation of life. Along with these an experiment by Louis Pasteur (1960) is also worth mentioning. His experiment may be mentioned below.
C. Experiment carried out by Louis Pasteur
- In a flask with sugar solution and yeast was heated to boil the solution and the mouth of the flask was fitted with a swan neck tube so that after heating the solution cannot be contacted with any external agent. After waiting for sufficient time no growth of yeast or other microbe was noticed in the flask.
- In a second experiment, a flask with a nutrient medium was heated and the mouth of the flask remained open. After a certain period of time, microbes were found to be developed in the flask.
- In another experiment, a flask with nutrient broth fitted with a swan neck tube was heated. After this the portion of the flask fitted with a swan tube was broken and within a certain period of time, microbes were found to be developed in the flask.
- When a flask with the nutrient medium was first boiled and then fitted with a plug in the mouth to prevent any contact with the outside, the flask did not develop any microbe inside.
All the figures above indicated these four experiments.
Louis Pasteur in his swan neck flask experiment showed that if the flask containing previously boiled cooled sugar solution with yeasts is prevented from contact with air, it can develop any microbe within the flask. Spallanzani in a different experiment kept some airtight containers, containing boiled nutrient medium and some opened containers containing the same type of nutrient medium. He observed afterward that the airtight flasks did not develop any microbes within the nutrient medium of the flasks. On the other hand, the containers that were kept open and in contact with air developed microbes within them. Therefore the experiments of Louis Pasteur and Spallanzani emphatically proved that life cannot be developed spontaneously.
Though the blue-green algae appeared as the first living form on earth, it is true that those were not the first life forms. The sudden appearance of any life form may be stated as spontaneous creation, which is the rejected concept of evolution. At the present state of knowledge evolution of any organism may occur through a process of gradual modification. However, in these gradual steps of modification, the origin of the replicative entity is the most important phenomenon. Organic evolution is quite a later event through which diversity in life forms has come into the establishment.
Among the proposers of the modern concepts on the origin of life, Alexander I. Oparin and J. B. S. Haldane were prominent. The concepts on the origin of life as proposed by Oparin in 1920 and in 1930 by Haldane have been accepted by all. Both scientists were proposers of chemical evolution behind the origin of the first life form. In 1953 Stanley Miller and Harold Urey by an ingenious experiment gave evidence in favor of this chemical evolution.
Though a precise definition of life is difficult to place, Kern and Kern in 1971 gave a definition of life in the following manner, “Life is a dynamic conscious entity with the power of reproduction”.
Time of Origin of Life
The oldest fossil record of a prokaryotic organism was obtained from a stone of 3.5 billion years of age. From this, it can be presumed that the first life appeared on Earth many years before this. However, the most prevailing idea is that the first life appeared within 1 billion years from the origin of Earth.
The Atmosphere on Earth when the First Life Arose
The primitive atmosphere of Earth which promoted the origin of life was absolutely different from the present-day condition.
- At that time there was no free O2 on the earth. The environment was principally full of nitrogen, CO2, and water vapor. Besides, there were H2S, NH3, CH4, etc.
- The temperature of the earth in this period was also very high and used to favor various chemical reactions.
- Frequently the occurrence of volcanic eruptions would increase the temperature of the earth.
- Besides this, in the sky of the primitive earth frequent electric sparking was a common event. High energy radiation also came from the sun and other celestial bodies.
- It is predicted that the reducing environmental condition of primitive earth helped to synthesize organic compounds from the interaction of inorganic substances.
Though it is believed that the primary life form was blue-green algae, it is very difficult to say emphatically that blue-green algae was the first life form on the earth. According to the modern view origin and evolution of life is a stepwise event among these events chemical evolution and the origin of replicating entities were very significant and the next event is biological evolution. From the beginning, the concepts as appeared regarding the origin and evolution of life may be noted in the following manner.
Theories on the origin of life in sequence:
|Theories||Proposer and Year||Essence of the Theory||Remarks|
|Special Creation||Suarez (1548 – 1617)||Life formation on earth has been possible by supernatural or divine forces.||No significance|
|Spontaneous Creation||Anaximander (611 – 547 BC) and Aristotle (384 – 322 BC)||Various life forms have originated spontaneously from non-living matters.||No evidence|
|Theory of cosmic origin||Richer (1965)||Early life arrived on Earth from some extraterrestrial source in the form of spores or germs with cosmic dust. Various forms of life then flourished from this.||By a specialties|
|Chemosynthetic theory||A. I. Oparin (1920) and J. B. S. Haldane (1928)||The gaseous elements of the earth reacted to produce small organic compounds under the influence of various environmental factors on the primitive earth. These compounds on polymerization produced the early form of life.||Scientific evidence|
Evidence in Favour of Chemosynthetic Theory
- Stanley Miller and Harold Urey conducted an experiment to support the chemosynthetic theory by Oparin and Haldane’s concept.
- In an experiment, Miller and Urey kept a mixture of methane (CH4), ammonia (NH3), and hydrogen (H2) in the ratio of 2 : 2 : 1 and water vapor at 800°C in a glass flask.
- Two electrodes were inserted to provide energy in the Spark Chamber at 75000 volts, which actually mimics lighting in the primitive Earth atmosphere.
- After a few days, Miller observed that the flask contained organic compounds such as amino acids.
A List of Organic Components Formed in the Miller-Urey Experiment:
- Glycolic Acid
- Lactic Acid
- N-Methyl Alanine
- a-Amino Butaric acid
- Succinic acid
- Aspartic acid
- Glutamic acid
- Formic acid
- Acetic acid
- Propionic acid
Several Reactions Leading to the Formation of Biomolecules
Several examples are given below on how simple gases might have produced organic molecules.
A. Formation of Hydrocarbon:
- 1. CH + CH → C2H2 (Acetylene)
- 2. CH2 + CH2 → C2H4 (Ethylene)
- 3. CH2+ CH2 → C + CH4 (Methane)
B. Formation of Hydrocarbon Derivative:
- C2H2 + H2O → CH3CHO (Acetaldehyde)
C. Formation of Organic Compound:
- CH3CHO + CH3CHO → CH3CHOHCH2CHO (Aldol)
- CH3COOH (Acetic acid) + CH3CH2OH (Ethyl Alcohol) → CH3COOCH2CH3 (Ethyl Acetate) + H2O
- 2CH3CHO (Acetaldehyde) + H2O → CH3COOH (Acetic acid) + C2H5OH (Ethyl Alcohol)
- 2CH2OHCHO (Glycol Aldehyde) + H2O → CH2OHCH2OH (Glycol) + CH2OHCOOH (Glycolic Acid)
- CH2OHCOOH (Glycolic Acid) + NH3 → CH2NH2COOH (Glycine) + H2O
Conditions that Sparked Life on Earth
Professor Shigenori Maruyama, Ken Kurokawa, and Dr. Toshikazu of the Hadean Bioscience project at the Tokyo Institute of Technology predicted when and how life was born on Earth. Early experiments of 1950 showed that it was possible for amino acids to be formed in water condensation within experimental conditions that mimicked the atmosphere of the early earth. In the experiments input of energy caused chemical reactions capable of synthesizing compounds based on carbon and nitrogen. The Hadean Bioscience researchers also gave importance to the specific environmental requirements for favorable chemical reactions to occur. Besides these environmental requirements life was impossible.
The Hadean Bioscience researchers predicted the nuclear geyser for the location where the first life appeared. The nuclear geysers during the Hadean era were having radioactive elements which upon breakdown released radiation. The radiation could react with surrounding water activating inert molecules and atoms producing a flow of electrons. As a result, water would be heated by the natural reactor. As a result, the acidic ocean was neutralized and nine favorable conditions for life could be generated.
- Prebiotic life to begin, a powerful energy source is required. The natural nuclear reactor would provide more than enough energy.
- As most organisms are made up of carbon, hydrogen, oxygen, and nitrogen these should be supplied constantly and these could be supplied from Early Earth’s crust along with the atmosphere.
- The elements for the formation of building blocks of organic compounds would be supplied from the earth’s surface.
- High concentrations of gases such as ammonia and methane being another requirement would be obtained from nuclear geysers.
- The dry-wet cycle was another requirement for life. Alternate hydration and dehydration would induce the formation of complex organic molecules such as RNA.
- Water was the primary location for the origin of life. But the water must be non-toxic and clean. The early oceans were highly acidic and salty and life could not be originated and survived there. Therefore, a pool or wetland within the land could be the site for the origin of life.
- Cellular protoplasm contains little sodium. Therefore, the water for first life should be poor in sodium.
- Besides these, there should be a day and night cycle and this is a vital condition for the origin of life. The day-night cycle may allow variation in temperature that would be conducive to various reactions leading to the origin of life.
- Finally, the diverse environmental condition is favorable for the promotion of life. Variations in pH, salinity, and temperature help different types of reactions form complex and varying organic compounds.
Only in nuclear geyser systems, these nine requirements for the origin of life could be possible. Therefore, nine requirements for the emergence of life may be indicated as under.
|Environmental Factors as Requirement||Presence in|
|1. Energy source (Ionizing radiation thermal energy)||Nuclear geyser system|
|2. Supply of nutrients||Nuclear geyser system|
|3. Constituent Element (CHON)||Nuclear geyser system|
|4. Reducing gas||Nuclear geyser system|
|5. Dry/Wet cycle||Nuclear geyser system|
|6. Na-poor water||Nuclear geyser system|
|7. Non-toxic water||Nuclear geyser system|
|8. Diversified environment||Nuclear geyser system|
|9. Cyclic nature||Nuclear geyser system|
Origin of Life Form
Though it is known how organic molecules may be originated, there is no evidence or information on the origin of life. As the primitive life form, we get only the fossils of prokaryotic organisms. However, it would not be illogical if we think there were several steps before the origin of the first prokaryotic life. The viruses support the existence of the living form having only nucleic acid and protein coat. Besides a virus appears to be a state between living and non-living. In this regard, the coacervate model of Oparin and the Microsphere model of Fox may be cited.
A. Coacervate Model:
Coacervate model (meaning to assemble together or cluster). According to Oparin (1924), in the history of the evolution of life, the coacervate was the first living form. Coacervate is regarded as an entity of protein, lipid, and carbohydrate enclosed within two coating layers as colloidal particles in a liquid phase and this form could grow in size by accumulating lipid from the environment. They also could multiply by budding. Oparin also suggested that coacervate could promote various types of chemical reactions. The coacervate model is not accepted now.
B. Microsphere Model:
S. w. Fox (1984) proposed this model. According to this model, the microsphere was the first cellular organism. As per the structural organization, the microsphere was mostly identical to the coacervate. However, the microsphere was principally made up of protein, enclosed within a semipermeable membrane. According to Fox, the microsphere could show anabolism-like formation of amino acid chains and nucleotide chains. Besides they can also multiply by budding. In the primitive crust of the earth, a microsphere-like structure was obtained. Therefore, the existence of microspheres as the initial life form cannot be ruled out.
Possible Steps in the Origin of Life Forms
On the basis of scientific ideas, from some fossil evidence and some experimental evidence we get a realization on the steps of origin of life and living form. It is presumed that there are five steps in the origin of the first cellular organism and that again in the anaerobic condition. The origin of different prokaryotes and eukaryotes organism in the aerobic atmosphere is an event at a later period.
The Steps on the Origin of Cellular Organism:
- Synthesis of organic compounds.
- Appearance of nucleic acid and protein.
- Association of protein and nucleic acid.
- Inclusion of nucleoprotein within the membrane.
- The appearance of the first cellular organism.
Different steps in the origin of life may also be shown by the following organizational changes in the atmosphere:
|1. Free Atoms||Hydrogen (H), Oxygen (O), Carbon (C), Nitrogen (N)|
|2. Inorganic Molecules||Hydrogen (H2), Water vapour (H2O), Carbon dioxide (CO2), Methane (CH4) and Ammonia (NH3)|
|3. Simple Organic Molecules||CH4 + H2O → Simple sugar, Fatty acids, Glycerol.
CH4 + H2O + NH3 → Amino acids.
CH4 + H2O + NH3 + HCN → Purines and Pyrimidines.
|4. Complex Organic Molecules||Sugars + Sugars → Polysaccharides
Fatty acids + Glycerol → Lipids
Amino acids + Amino acids → Proteins
Purines/Pyrimidines + Sugars + Phosphates → Nucleotides Adenosine Phosphates
Nucleotides + Nucleotides → Nucleic acids
|5. Coacervates||Aggregates of large organic molecules capable of growth and division.|
|6. Protobionts||Nucleic acid-controlled coacervates.|
|7. Primitive Cells||Lipo-protein membrane-bound structures with enzyme-controlled metabolism and nucleic acid regulation.|
From the above table, it appears that in the primitive earth, there was no life at all. The atmosphere was full of free molecules such as H, O, C, and N. Inorganic molecules are then generated. Following this simple organic molecules appeared and these lead to the development of complex organic molecules. The organic molecules were aggregated to form a coacervate-like structure. Ultimately nucleic acids are enclosed within coacervate and developed protobiont. This led to the formation of primitive cells. All these steps may be shown in the following diagram.
Eukaryotes also took some prokaryotes into their own cells. These prokaryotes live in a symbiotic relationship with the host cell. The organisms making up the cell work together and help each other. After so many millions of years of living together, the pieces of the cell could not survive alone now. The prokaryotes have become endosymbionts, life forms living within a host organism. They still have their own DNA and divide by binary fission just as they did when they were wild and free.
Now, the interior of the eukaryotic cell is a very comfortable environment for them. The eukaryotic cell protects them from contact with oxygen, which is poisonous to prokaryotes, and provides a stable environment with water and the necessary chemicals for their life processes and reproduction. The following schematic diagram shows, the formation of advanced organisms from ancient organisms due to evolution: