Biology · Evolution · NEET
Almost, but be careful. Chemical evolution is the overall process: non-living inorganic molecules slowly turning into complex organic molecules and finally into the first life. The Oparin-Haldane theory is the specific proposal (1920s) that this chemical evolution actually happened on early earth. So chemical evolution is the idea, and Oparin-Haldane is the theory that explains it. For NEET, treat them as linked: Oparin-Haldane theory = the theory of chemical evolution.
No. Oparin (Russia) and Haldane (Britain) only proposed the theory in the 1920s using ideas and reasoning. They did not do a lab experiment. The famous experiment that tested and supported their theory was done in 1953 by S.L. Miller (with Harold Urey). Students lose marks by mixing these up. Oparin-Haldane = the theory; Miller-Urey = the experiment that proved it possible.
Oparin proposed that organic molecules in the early ocean joined into tiny droplets called coacervates (protein-lipid-carbohydrate aggregates). These droplets could take in molecules, grow, and split, so they behaved a little like living cells. They are the pre-cell stage, also called protobionts. NEET may ask 'who proposed coacervates?' The answer is Oparin.
Yes, the early atmosphere was reducing (no free oxygen). It had water vapour, methane (CH4), ammonia (NH3), hydrogen (H2) and carbon dioxide, released from the molten earth. Free oxygen would have destroyed the new organic molecules by oxidising them. Only later, after photosynthesis began, did oxygen build up. This reducing, oxygen-free condition is a must-know point for chemical evolution.
It is a modern form of abiogenesis, but a very special one. Classic abiogenesis (spontaneous generation) said life appears suddenly and fully formed from dirt or dead matter, which Pasteur disproved. Oparin-Haldane says life came from non-living matter too, but slowly, over millions of years, by chemical evolution, only once, under early-earth conditions. NCERT calls this 'a version of abiogenesis.' Do not confuse it with the disproved spontaneous generation.
Which of the following is the correct sequence of events in the origin of life? (i) Formation of protobionts (ii) Synthesis of organic monomers (iii) Synthesis of organic polymers (iv) Formation of DNA-based genetic systems
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A.I. Oparin, a Russian scientist, and J.B.S. Haldane, a British scientist, proposed it independently in the 1920s. Because both reached a similar idea, NEET writes their names together as the Oparin-Haldane theory of chemical evolution.
Chemical evolution is the slow formation of complex organic (life) molecules from simple non-living inorganic molecules on early earth, before the first cell appeared.
Water vapour, methane (CH4), ammonia (NH3), hydrogen (H2) and carbon dioxide. There was no free oxygen, which is why the atmosphere is called reducing.
Energy came from UV radiation from the sun, lightning and electric discharges, and heat from the earth. This energy made the simple gases react to form organic molecules.
They are tiny droplets of organic molecules (proteins, lipids, carbohydrates) that could grow and divide. Oparin called them coacervates; they are the non-living pre-cell stage before true cells appeared.
Origin of life is a scoring, direct-recall part of the Evolution chapter. NEET regularly asks the correct sequence of events, the reducing gases, who proposed coacervates, and how Oparin-Haldane differs from spontaneous generation.
