Origin of life

From ArticleWorld

The origin of life is an area of biology in which research is limited. Even though this field has been of value to biology and the understanding of the natural world it is still not well researched. This may be due to the fact that the progress of work in this area is slow. It is now known that there are some conditions in which life may have emerged however the mechanism by which life came from non-life is still unknown.

History

The first theory about the origin of life was postulated by Aristotle. He suggested that life came about by spontaneous generation or abiogenesis. His theory was that life cam about from non-living matter such as maggots being generated from rotting meat. His theories were eventually disproved in the 18th century by the experiments of Louis Pasteur. He showed that a sterile environment would remain sterile forever and that living organisms came only from other living organisms. The "Law of Biogenesis", or "all life from an egg" based on his work is now a key principle of modern biology.

The term abiogenesis now is used to address the ultimate origin of life. Pasteur proved that this was not possible for complex organisms. When Charles Darwin put forward his theory of evolution he described a mechanism where organisms might change or evolve over long periods of time, millions of years, from their simple forms to the complex forms seen today. He still could not however address the problem of the origin of life. He suggested in correspondence with J.D. Hooker that life could have started in a "warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity, etc. present, [so] that a protein compound was chemically formed ready to undergo still more complex changes". He also believed that the presence of life in fact prevents spontaneous generation from occurring today.

It was not until the 19th century that a scientist called Oparin showed in his "The Origin of Life on Earth", that atmospheric oxygen and other sophisticated life-forms prevented the events that would lead to the evolution of life. He said that a "primeval soup" of organic molecules can be created in an oxygen deficient environment through the action of sunlight. These would combine in a complex fashion until they dissolve into a coacervate droplet which would grow and reproduce and factors that promote cell integrity would survive. This is considered as a starting point in the search for the origin of life.

Current models

Presently there is no standard model of the origin of life but most accepted models build on discoveries concerning the origin of molecular and cellular components of life. Some of these include:

• Pre-biotic conditions resulting in the creation of certain basic small molecules of life.
• Phospholipids spontaneously form a lipid bilayer one of the basic components of a cell membrane.
• The polymerization of nucleotides into random RNA may have resulted in self-replicating ribozymes.
• Proteins out-compete ribozymes and become the dominant polymers of catalytic reactions.