What is LIFE?" Life is the power a
living thing possesses to maintain its existense ; reproduce and ensure its survival."There's an evidence that the
earth was
formed about 4700 million years ago. At the time of its formation, the earth was like a hot ball of fire and no life was possible on it. Gradually the earth began to cool and its matter began to condense so that SOLIDS,LIQUIDS and GASES could co-exist. Recent studies suggest that life started about 3600 million years ago as a
simple one-celled
organisms.But after all, how did life originated on earth is still a question of interest and anxiety. Certain theories on "Origin of Life" were acknowledged world-wide and put forward to make people believe what they stated. To name a few ,they were:Theory Of Special Creation (God created everything), Theory of Spontaneous Generation (life happened on its own from non-living things) & Cosmos Theory (life came from the outer space). All these olden theories about "Origin of Life" were baseless without any scientific reasoning behind what they stated. Hence, all of them were disapproved by the scientific community.But then was needed a logical and a more scientific approach to solve this mystery of "The Origin of Life".Let's now have a look at what the brains of today have to say about this.Origin of the Solar SystemIt is understood that sun and the planets were formed from a cloud of cosmic gases and dust.Most of this gas and dust began to condense rapidly into a compact contracting mass.Enormous heat and pressure were produced by the condensation due to which thermo-nuclear reactions were intitiated and the main condensed mass transformed into the sun.The remaining gas cloud formed a disc which was held by the gravitational field of the newly born sun. The planets were also formed by the contraction and condensation of the remainder cloud of cosmic dust and gas.Chemical EvolutionBaby earth had innumerable free atoms of all those elements (Hygrogen, Nitrogen, Oxygen, Phosphorus, Carbon, Sulphur etc.) which were essential for the formation of Life - a simple Protoplasm and hence a unicellular organism. Free atoms combined to form
molecules and simple inorganic compounds.The Primitive Atmosphere was a reducing atmosphere as Hydrogen was abundant in the atmosphere hence chemically reducing.Compunds like Ammonia,Carbon Dioxide,Water,Nitrides and Carbides were the main chemical constituents in the evironment.Water vapour and metallic carbides reacted to
Form the first natural organic compound, methane.As rain rushed down ,it must have dissolved away and carried with it salts and minerals and accumulated in the form of oceans. Thus ancient oceanic water containes large amounts of dissloved ammonia, methane, hydrogen cyanide, nitrides and carbides. These organic compounds were enough for the formation of simple simple sugars ( e.g., ribose, deoxyribose, glucose etc ) , nitrogenous bases ( eg. purines and pyrimidines), amino acids, glycerol, fatty acids etc. In presence of solar radiations and thunder lightning these compounds reacted to form poly-saccharides, fats, protiens and hence Bio-Molecules like nucleotides, polypeptides, which polymerised into Nucliec Acids( DNA and RNA).So all these building blocks of life were present in the oceans of the primitive earth.Biological Evolution : The Origin of Bios (Life)The large organic and bio molecules which were synthesized abiotically (without involving any life form) on Primitive Earth interacted due to molecular reactions and intermolecular attraction and formed Colloidal Aggregates (jelly like droplets). Such water bound aggregates had been named as Microspheres and later they were known as Coacervates.A coacervate was a cluster of macromolecules surrounded by a membrane or a covering layer. Inside this membrane was enclosed a colloidal jelly like mass containing a mixture of proteins, nucleic acids, lipids, polysaccharides and other biologically important molecus. These coacervates grew by absorbing molecules from the surrounding environment. They could divide by Budding. Many reactions like decomposition of glucose took place inside the coacervates.So coacervates were the sole living molecules which gave rise to cells.The first living thing the Proto-Cell originated in ocean.The protocells were in fact clusters of nucleo-proteins, which surrounded organic substances as nutrients for replication (reproduction in lower forms of life).These primtive cells absorbed energy from dissolved chemicals in the oceans.The protocells became more independent and acquired capacity for better utilization of energy and evolved into Prokaryotes. Prokaryotes like bacteria were the first living cell in the complete and correct sense.Mutations occured in their DNA which caused changes to their structure and constitution. As these chemical and structural changes continued photosynthesis in cells and respiration came into existence.Such organisms formed uni-cellular plants and later on mobile cells like amoeba and paramoecium emerged. Autotrophic organisms developed from such highly complex cells and hence small plants were formed and small and tiny animals came into existence.These living organisms adapted themselves to their surroundings and hence more changes occured in their structures and compositions leading to more complex and intelligent organisms with better feeding mechanisms and better defence and ofensive techniques. This led to spreading of living creatures all over the earth and now our earth was no longer a dead planet.Life was born and is present till date on our EARTH.
More abstracts about the Origin of Life