Life is a fundamental thing in the way that animal, plants and other molecules operate within the earth and to some extend other planets that are found within the solar system. Scientist, researchers, psychologist and historians have different perspective on the origin of Life. Although there is the single perspective that is accorded and embraced by religious communities, that life began through the directive of God, which is the fundamental and well-known aspect of origin of life. However, different perspectives are illustrated by scientist and researchers a position that this paper concentrates. Thus, the paper concentrates and analyzes the following hypothesis and theories: Prebiotic Earth, Stanley Miller Experiment, Spontaneous Generation, the RNA Hypothesis, Liquid Hypothesis, Iron Sulfur World Theory, Clay Theory, Self-Assembly Process and Primordial Soup Theory.Pre-biotic EarthThis perspective tries to show that life began approximately five billion years ago. The solar system was made up of dust and gases that used to revolve and swirl around a white-hot core. However, when the white-hot core reached one million degrees Fahrenheit, the sun was born.
At the same time, the dust and gases condensed and formed the asteroids. It is believed that there were many planetesimals and asteroids when the solar system was formed. Thus, when the particles were revolving around the sun, they collided, while others combined making the planetesimals to grow larger; a process is commonly known as accretion. The formed asteroids released enormous amount of energy and radioactivity that contributed in the melting of the earth’s crust. Hence, the activity of radioactive caused the building up of gases and heat, which contributed in causing volcanoes, and various gases were trapped under the safe of the earth. The volcanoes erased earlier or original craters (Fernando, 2007).Moreover, has the meteorites continued to hit the earth, water was released and combined with carbon dioxide and other gases forming clouds. The clouds formed the shield against the sunrays and reduced the intensity of the meteorites cooling the earth surface (Hazen, 2007).
Thus, the clouds began pouring rain cooling the constituents’ of volcanoes resulting in the creation of oceans and lakes.Stanley Miller ExperimentStanley Miller collaborating with Harold Urey at the University of Chicago carried out an experiment utilizing chemicals to understand hypothetical origin of life (Ulmschneider, 2006). They were basing their experiments on the findings of Haldane and Alexender Oparion hypothesis arguing that the origin of life is attributed to the synthesizing of organic compounds. The experiment took place in 1953 in which they used methane, water, hydrogen and ammonia. These chemicals were put in sealed glass tubes and flasks that were connected in a loop. One of the flask was half filled with water while the other contained electrodes that could act as imaginary lightning. The water then was heated to produce vapor and sparks were introduced.
This concoction was then cooled for the water to cool and condense to enable the continuous loop/cycle. Within a week, Miller and Urey discovered that the carbon about 10-15% was converted into organic compounds, 2% had formed amino acids an ingredient of making proteins. Nevertheless, this was the foundation that inspired other experiments such as the one conducted by Juan Oro in 1961 in which he found out that a combination of ammonia and hydrogen cyanide in presence of water formed nucleotide base adenine.Spontaneous GenerationThis hypothesis view that life on earth is attributed to non-living material. For example, it postulates that rats originate from hay, fleas from putrid matter while crocodiles originate from rotting logs.
Supporters of this perspective believe that there is an active principle – the vital élan, which is the source of life under a common theory that is referred to as vitalism. However, this perspective was reputed by experiments that were carried out by other scientists such as Redi and Pasteur. In 1668, Francisco Redi proved that maggots appeared on meat when the meat was exposed to the environment while in 1862 Louis Pasteur experiment showed that spontaneously hypothesis did not fulfill its basis in an environment that is sterile and nutrient rich media (Ulmschneider, 2006).The RNA HypothesisThis hypothesis postulates that proteins were not present in the biochemical reactions and RNA played an important role in the storage of information and other catalytic roles that were necessary for primitive self-replicating system with the absence of DNA and proteins. Various experiments have been carried out to try proving this hypothesis. For example, the experimental support as shown that RNA enzyme (Ribozymes) which translates the RNA into proteins. Another example is the early cell membranes that could have formed spontaneously from proteinoids, which forms microspheres the same as those in the membrane-enclosed compartments.
Lipid HypothesisThis hypothesis postulates that lipid-like was the first self-replicating object. This is attributed to the fact that the phospholipids form bilayers in water when it is under agitation, an occurrence the same as the structure of cell membranes. Moreover, the lipid-like bodies expand followed by spontaneous splitting, which maintains the same composition and size as the proceeding lipid. Thus, the main argument that is postulated by this argument is that the lipid bodies are the foundation of storage of information and its evolution as contributed in the appearance of polymer entities e.g. the DNA and/or RNA that can store information better. However, no specific research or experiment in terms of biochemical that supports lipid hypothesis.Iron Sulfur World TheoryThis theory was championed by Gunter Wachtershauser a chemist who stated that the life on Earth had its roots on hydrothermal.
This theory employs the same perspective as the approach that life originated near the submerged hydrothermal vents. This idea is also based on the closed metabolic cycle e.g. the citric acid cycle, which results in the formation of life spontaneously. His hypothetical perspective was that acetic acid (a combination of hydrogen, carbon and oxygen) played a major role in the metabolism of cells (Walther, 2008). Thus, trying to prove that the acetic acid is a factor in occurrence of life and production of proteins, he gave the following steps: production of acetic acid, which can be obtained from metallic ion catalysis, them carbon is added to the acetic acid molecule resulting in a three-carbon pyruvic acid in which ammonia is added to form amino acids. This then results in the production of peptides a constituent of proteins. It is usually termed as more of citric acid cycle because of the presence of pyruvic and acetic acid.
Of late (1997), and with the help of Claudia Huber, they were able to mix iron sulfide, hydrogen sulfide, iron sulfide and carbon monoxide and putting them into a temperature of 100 degrees Celsius resulted in the formation of amino acids and they advanced the research and they were able to produce peptides (Ulmschneider, 2006).Clay TheoryGraham Cairns-Smith proposed this theory in 1985 at Glasgow University. His hypotheses attributed that life began on clay. The theory view that complex organic molecules arise gradually from non-organic replicates that already exists e.g. the silicate crystals in a solution.
Thus, complexity in the companion molecules results due to selection of pressures on specific clay crystal helps in replication of organic molecules without prior knowledge or help from the original silicate (Dworkin, & Falkow, 2006). Few scientists acknowledge this perspective and compounded by the fact that Cairns-Smith is a critic of other hypothesis of origin of life, he accepts that his hypothesis has some weak points (Alberts, & Wilson, 2007).Self-Assembly ProcessThis theory bases its roots on the understanding that life is constituted of cells. Through the understanding of the pre-biotic Earth, there were no large molecules such as those of proteins and nucleic acid and thus any life may have originated from self-assembly process. Moreover, this possibility is compared in the way that the soap or foam bubble occurs.
Thus, in the origin of life, certain organic compounds known as the amphiphilic molecules were able to self-assemble forming the microscopic structures (Dworkin & Falkow, 2006). Hence, the spontaneously forming structures contribute in the formation of the original membrane that is required for the cellular life to begin. This aspect can be seen in the growing of lipid bilayers when additional amphiphilic compounds are present.
This is attributed to the fact that the primitive cell has no capability of replication in its macromolecular components unless the membrane is elastic to increase internal growth. Thus, experiments that have been carried out using liposome have indicated that through self-assemble lipids grow into lipid bilayers.The Primordial Soup TheoryThis research was carried out by Oparin and Haldane in 1924 and forms the basis that was used by Miller and Urey in their experiment. They supported the theory of spontaneous generation of life that was disapproved by Pasteur in that it was inhibited by atmospheric oxygen. Thus, the oxygen prevents the synthesis of some organic compounds that play an important role in evolution especially in terms of the building blocks.
The scientists acquires that the inhabitation of the spontaneous generation is attributed to the fact that the current conditions are different from earlier earth conditions e.g. the current presence of organisms. Thus, they proposed that it could be possible to develop “primeval soup” organic molecules within an area that has less oxygen, but with the presence of sunlight (Alberts, & Wilson, 2007).
Hence, if this approach is utilized it will enable the creation of coacervate droplets that forms the foundation for organisms to develop. Nevertheless, the presences of the droplets enable the growth by fusion and reproduce through fission, which then promotes for cell integrity. Hence, this perspective of ‘primeval soup’ has been used as the foundation of modern theories of life.ConclusionOrigin of life is an aspect that has not been fully embraced by the society because of the different views that religious and non-religious community. Prebiotic is traced to the contribution of the solar system is creating life. Stanley Miller Experiment concentrated on the contribution of organic molecules in creating life, a foundation that is shared by other theories and hypothesis championed by other researchers like the Primordial Soup theory. Other theories that play important role in tracing the origin of life are the Lipid hypothesis and the RNA hypothesis revolves on bringing together various compounds resulting in the creation of life.ReferencesAlberts, B.
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