Biology · Evolution · NEET
Yes, the classical theory of spontaneous generation is a form of abiogenesis (life from non-living matter). But there is a trap for NEET. The OLD spontaneous generation idea claimed complete, ready-made organisms appear suddenly from rotting matter (straw, mud) in a short time. Pasteur disproved THIS version. The modern Oparin-Haldane 'chemical evolution' is also technically abiogenesis, but it means life formed slowly over millions of years from simple organic molecules. Do not mix the two: Pasteur killed the quick-and-dirty version, not chemical evolution.
NCERT is very precise here. Pasteur took pre-sterilised (boiled) flasks with killed yeast. In the flask that stayed protected/sterilised, life did NOT come from the killed yeast. In another flask left open to air, new living organisms arose. This showed the organisms came from the air (pre-existing life), not from the dead yeast itself. So life comes only from pre-existing life, and spontaneous generation was dismissed once and for all.
This is the exact gap NCERT points out. Pasteur proved present-day life comes only from earlier life, but that did NOT explain the first life on early Earth. That question was answered later by the Oparin-Haldane theory of chemical evolution, where the first life arose slowly from pre-existing non-living organic molecules. So Pasteur closes one door (sudden spontaneous generation) and opens the need for the next concept (chemical evolution).
Because the microorganisms/spores were floating in the air. The open flask let air (and its living spores) reach the killed yeast, so new organisms grew there. The pre-sterilised, protected flask kept air-borne life out, so nothing grew from the dead yeast. The dead yeast could not generate life on its own. This is the single most important observation to remember for NEET.
No. Spontaneous generation = complete organisms appearing suddenly from decaying matter (disproved by Pasteur). Chemical evolution (Oparin-Haldane) = simple inorganic molecules slowly forming organic molecules, then the first non-cellular life, over millions of years. NEET often frames statements to test if you can tell these apart. Pasteur rejected spontaneous generation; he did not reject chemical evolution.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the old belief that life came out of decaying and rotting matter like straw and mud on its own. NCERT lists it just before Pasteur's experiment. It was disproved by Louis Pasteur.
By careful experimentation with sterilised flasks, Pasteur demonstrated that life comes only from pre-existing life. New organisms grew only in the flask open to air, not in the protected sterilised flask.
No. NCERT clearly states his experiment disproved spontaneous generation but did not answer how the first life form came on Earth. That was addressed by the Oparin-Haldane theory of chemical evolution.
Panspermia is the idea that units of life called spores came to Earth from outer space. It is a separate origin-of-life idea from spontaneous generation and from chemical evolution, and is still favoured by some astronomers.
Yes. Origin-of-life theories are direct one-line NCERT statements. NEET repeatedly tests who disproved spontaneous generation (Pasteur) and the sequence of theories, so memorising the exact NCERT wording is high-yield.
