They are the link between living and non-living; so they might be the first organisms to be formed from a non-living environment.

The primitive atmosphere of Earth had water, methane and ammonia.

According to this theory, life is distributed throughout the cosmos in the form of resistant spores of living organisms known as cosmozoa.

The event of formation of Earth and other planets by explosion of a single homogenous matter, i.e. yelm,  was termed as big bang.

The energy for autotrophism was totally obtained from anaerobic breakdown.

According to this theory, life is distributed throughout the cosmos in the form of resistant spores of living forms known as cosmozoa. This theory was supported by H. F. C. Crick in his book 'Life Itself - Its Origin and Nature'.

A sea containing organic substances, which on polymerisation can give rise to biomolecules, was termed as hot dilute soup.

He gave symbiotic theory.

The free oxygen produced by the blue-green algae converted the atmosphere from reducing into oxidising.

They were the first formed primary organisms that appeared during the early period.

Miller and Urey showed that amino acids like glycine and alanine and even more complex compounds can be synthesised in vitro and proved the biochemical theory of origin of life.

They were capable of replicating themselves but were not membrane-bound.

The first living cell arose from simple inorganic and organic compounds; a phenomenon called abiogenesis.

He proved with goose-neck flask that air contains spores of microorganisms. Thus, biogenesis theory was strongly supported by Pasteur's experiment.

He presented the biochemical explanation of origin of life in his book 'The Origin of Life on Earth'.