First Life

Theory of special creation
This theory explains that all the life on the earth have been created by god. The various types of organism are believes to exist in the same form and have not change since their creation. This theory is based on religious believe which do not required obserption and experimentation to find out the truth. The scientific at axidences do not support this theory.

Theory of Abiougenisis
This theory was purpose by von-Helmont(1577-1644). He stated that; life is originated from non-living substances spontaneously. He proposed that mice will be developed when human sweat and wheat floor kept together for 21 days. Similarly, Aristole told that, worms, insects, fish, frogs developed from filts and soil. This theory also propose the formation of maggots(larva of fly) from decaying meat. But this theory is discarved the theory of Biogenetic.

Biogenetic theory
This theory state that, life is originated from preexisting life. This theory is just opposite to theory of Abiogenesis. But it does explain the origin of first life. This theory is proposed by Louis Pasture (1864AD) and spallanzani (1865AD).

Cosmozoan theory
It was propose by Sichter in 1865 AD. It state that, life on earth came from another planate in the form of seed or spore, called panspermia. But this theory couldn’t explain that who would come to the earth.

Modern theory of origin of life or
Naturatistic theory of origin of life
This theory was given by AI Oparin(1923) and later supported by JBS Haldane (1923). This theory is also called Oparin-Haldane theory. They explained life was originated from non-living chemicals. Here the chemical evolution took place from simple chemical compound to complex chemical compound and simple life was originated after a long span of time.
Modern theory of origin of life is divided into the following heading:
Formation of simple inorganic chemical compound
Formation of simple organic compound
Formation of complex organic compound
Formation of molecular aggregate or coecervate
Formation of first life
Development of chemosynthesis
Development of photosynthesis