We salute the spirit of
inquisitiveness of man, which gave birth to the discipline of science. The same
spirit of questioning also led man to often wonder how life or the first
organism cane into existence. This quest led him to find answers to how, when
and where life originated.
For centuries, it was believed that
life originated de movo. In addition several other scientific and
non-scientific theories were also put forward. Some of them are
Theory of special creation: (or Biblical theory)- It was forward by
Father Suarez, a Spanish Monk
.
Theory of spontaneous generation (or
Abiogenesis): (Gr, ‘a’ – absence, “bios” –life, genesis” – origin) or
origin from nonliving matter.
Theory of Panspermia or Cosmozonic Theory: According to this theory , life came from
some other planet
Biogenesis: Francesco Redi and Louis Pastur
laid the foundation for the Theory of Biogenesis, which propounded that living
organisms arise from pre-existing ones and not from non –living matter.
Chemosynthetic Theory or Chemogeny:
This theory proposes that first form of life originated from inorganic chemical
elements by formative action of some
external physical force viz. lightening or cosmic rays, etc. It was put forward
by A.I. Oparin and J.B.S. Haldane
and the experimental evidence was provided by Stanley Millar & Harold Urey. For example, Mighi meteorite in Ukraine and analysis of another meteorite
content viz Murchisin, Victoria in
Australia by space biologists also revealed similar composition indicating
that similar processes are still occurring elsewhere in space. However, in this
case, although the presence of amino acids and polynucleotide are similar to
DNA, these are of chemical origin and therefore have identical strands instead of
complementary strands.
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