Spores

Panspermia

Gamets

Sperms

Formation of organic monomers from inorganic gases

Presence of free oxygen in the early atmosphere

Polymerization of monomers to form macromolecules

Coacervates as precursors to the first cells

4.5 billion

1 billion

500 million

2 billion

Palaeobotanist

Zoologist

Ornithologist

Palaeozoologist

Chemosynthesis

Fermentation

Photosynthesis

Respiration

A R Wallace

Francisco Redi

Louis Pasteur

A I Oparin

${{\rm{N}}_2}{\rm{ \,and \,}}{{\rm{H}}_2}{\rm{O}}$

${{\rm{H}}_2}{\rm{O \,and\, C}}{{\rm{H}}_4}$

${\rm{C}}{{\rm{H}}_4}{\rm{\, and\, }}{{\rm{N}}_2}$

${\rm{C}}{{\rm{O}}_2}{\rm{\, and\, N}}{{\rm{H}}_3}$

Amino acids

Nucleic acids

UV radiations

Microspheres

Polymerization → Synthesis of monomers → Protobiont formation → DNA-based genetic systems

Synthesis of monomers → Polymerization → Protobiont formation → DNA-based genetic systems

Protobiont formation → Synthesis of monomers → Polymerization → DNA-based genetic systems

DNA-based genetic systems → Protobiont formation → Polymerization → Synthesis of monomers

Methane ($CH_4$)

Ammonia ($NH_3$)

Water vapor ($H_2O$)

Oxygen ($O_2$)

$cms$

Metres

${A^0}$

Light years