Key Fact
Origin of life
Big Bang ~13.7 bya; Earth ~4.5 bya. Oparin-Haldane: chemical evolution from primordial soup. Miller-Urey (1953): CH4, NH3, H2, H2O + spark → amino acids. Panspermia: life from space.
-- NCERT Class 12 Biology, Ch. 6, p. 111Origin Life Panspermia
8 MCQs9-step worked example
Source: NCERT Genetics and EvolutionOfficial key: NTA-verifiedLast updated: 27 Sep 2026
Origin Life Panspermia, explained for NEET
The high-frequency trap in origin-of-life questions: confusing what Miller-Urey actually synthesised (amino acids and simple organic molecules) with what Oparin-Haldane predicted as the precursor stage (coacervates / protobionts). NEET distractors exploit this gap — expect options listing nucleic acids or proteins as Miller-Urey products.
Oparin-Haldane hypothesis (chemical evolution). Life arose from inorganic molecules through a stepwise process on primitive Earth. The early atmosphere was reducing — rich in CH₄, NH₃, H₂, and H₂O vapour (no free O₂). Energy from UV radiation and lightning drove chemical reactions that formed simple organic molecules, which accumulated in warm water bodies ("primordial soup"). These monomers polymerised → complex organic molecules → self-assembling coacervates → primitive cells. Key point: this is abiogenesis — life from non-life (NCERT Class 12 Biology Chapter 6, page 111).
Miller-Urey experiment (1953). Stanley Miller and Harold Urey tested the Oparin-Haldane hypothesis experimentally. They sealed CH₄, NH₃, H₂, and H₂O in a closed apparatus, passed electric sparks (simulating lightning) for a week, and analysed the condensed products. Result: amino acids (glycine, alanine, aspartic acid), hydroxy acids, and other simple organic compounds formed abiotically. They did NOT produce DNA, RNA, proteins, or cells — only monomers.
Panspermia (cosmozoic hypothesis). An alternative proposal: life did not originate on Earth but arrived via meteorites or cosmic dust from elsewhere in the universe. This does not explain origin — it merely transfers the question to another location. NCERT mentions it as a contrast to chemical evolution.
Watch-out for NEET: Questions often pair panspermia with Oparin-Haldane as options to test whether you know panspermia is about transfer, not origin mechanism. Also watch for distractors that claim Miller-Urey synthesised proteins or nucleotides.
Can you answer these Origin Life Panspermia MCQs?
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
MCQ 1Easy RecallPractice
According to the Oparin-Haldane hypothesis, the primitive atmosphere of Earth was:
Show answer and why every option is right or wrong
Answer: C. Oparin and Haldane proposed a reducing atmosphere containing methane, ammonia, hydrogen, and water vapour with no free oxygen (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because Oparin-Haldane explicitly proposed NO free O₂; an oxidising atmosphere would decompose organic molecules before they could accumulate.
Why B is wrong: B is wrong because the present atmosphere is oxidising (21% O₂) — the opposite of the proposed primitive atmosphere.
Why D is wrong: D is wrong because ozone requires free O₂ to form via UV photolysis, which was absent in the early atmosphere.
MCQ 2Easy RecallPractice
In the Miller-Urey experiment, which energy source was used to simulate natural conditions on primitive Earth?
Show answer and why every option is right or wrong
Answer: D. Miller and Urey used electric discharge (sparks) to simulate lightning as the energy source driving abiotic synthesis (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because radioactive decay was not the energy source used in the Miller-Urey apparatus, though it existed on primitive Earth.
Why B is wrong: B is wrong because geothermal energy relates to deep-sea hydrothermal vent hypotheses, not the Miller-Urey experimental setup.
Why C is wrong: C is wrong because although UV radiation is mentioned in the Oparin-Haldane hypothesis as a natural energy source, Miller-Urey specifically used electric sparks, not UV lamps.
MCQ 3Easy RecallPractice
The Miller-Urey experiment successfully produced:
Show answer and why every option is right or wrong
Answer: B. The experiment yielded amino acids (glycine, alanine, aspartic acid) and other simple organic molecules — monomers only, not polymers or nucleic acids (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because nucleotides were NOT formed in the Miller-Urey experiment; only amino acids and simple organics were produced.
Why C is wrong: C is wrong because proteins are polymers requiring peptide bond formation and ribosomal machinery — the experiment produced only amino acid monomers.
Why D is wrong: D is wrong because coacervates are Oparin's theoretical aggregates representing a later stage of chemical evolution; they were not a product of the Miller-Urey apparatus.
MCQ 4Concept TrapPractice
NCERT notes that after Miller produced amino acids in his flask, "analysis of meteorite content also revealed similar compounds indicating that similar processes are occurring elsewhere in space." A classmate argues that this finding directly proves the panspermia hypothesis (that life reached Earth from outer space). What is the flaw in this argument?
Show answer and why every option is right or wrong
Answer: A. The meteorite observation supports chemical evolution being a general process (organic molecules can form abiotically elsewhere too), but panspermia is a distinct claim — that life or its building blocks were physically transported to Earth. Finding similar compounds elsewhere shows the process can repeat; it says nothing about transport actually happening. NCERT Class 12 Biology Chapter 6, page 111.
Why B is wrong: B is wrong because showing the same synthesis process occurs elsewhere is evidence for chemical evolution being universal, not evidence that material was carried to Earth — panspermia specifically requires transport, which the meteorite-composition finding does not demonstrate.
Why C is wrong: C is wrong because NCERT explicitly states meteorite analysis revealed similar compounds — treating this as an error contradicts the given text.
Why D is wrong: D is wrong because the temperature Miller used simulated volcanic-storm conditions for HIS experiment; it says nothing about the temperature history of a meteorite, and the comparison being drawn is about the type of compounds formed, not the conditions of formation.
MCQ 5Direct ApplicationPractice
Which gas was specifically ABSENT from the gas mixture used in the Miller-Urey experiment?
Show answer and why every option is right or wrong
Answer: B. The Miller-Urey apparatus contained CH₄, NH₃, H₂, and H₂O vapour — free O₂ was deliberately excluded because its presence would oxidise and decompose organic products (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because methane was one of the four components used to simulate the reducing atmosphere.
Why C is wrong: C is wrong because ammonia was included as a nitrogen source in the gas mixture.
Why D is wrong: D is wrong because hydrogen gas was part of the reducing mixture in the apparatus.
MCQ 6Concept TrapPractice
A student claims: "The Miller-Urey experiment proved that life can arise spontaneously from inorganic chemicals." Which statement best corrects this claim?
Show answer and why every option is right or wrong
Answer: A. Miller-Urey demonstrated abiotic synthesis of amino acids (step 1 of chemical evolution) — this is far from "life arising spontaneously." The gap between amino acids and a self-replicating cell involves polymerisation, membrane formation, and genetic machinery — none of which the experiment addressed (NCERT Class 12 Biology Chapter 6, page 111).
Why B is wrong: B is wrong because Miller-Urey tested the Oparin-Haldane (chemical evolution) hypothesis, not panspermia — and it did not prove any theory completely.
Why C is wrong: C is wrong because no living cells were produced in the experiment; only simple organic monomers formed.
Why D is wrong: D is wrong because the experiment supported (not disproved) the first step of chemical evolution by showing organic molecules can form without life.
MCQ 7Direct ApplicationPractice
Which of the following correctly distinguishes the Oparin-Haldane hypothesis from the theory of panspermia?
Show answer and why every option is right or wrong
Answer: C. Oparin-Haldane: life originated on Earth through chemical evolution (inorganic → organic → coacervates → cells). Panspermia: life/precursors arrived from outer space. They differ in the location of origin (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because the labels are reversed — Oparin-Haldane is the terrestrial hypothesis, panspermia is the extraterrestrial one.
Why B is wrong: B is wrong because neither Oparin-Haldane (primordial soup) nor panspermia (extraterrestrial transfer) is specifically a hydrothermal vent hypothesis.
Why D is wrong: D is wrong because coacervate formation is a concept from Oparin's terrestrial chemical evolution model, not from panspermia.
MCQ 8Direct ApplicationPractice
Arrange the following events in the correct sequence according to the theory of chemical evolution:
(i) Formation of coacervates
(ii) Synthesis of simple organic molecules
(iii) Formation of primitive cells
(iv) Polymerisation of monomers
Show answer and why every option is right or wrong
Answer: D. Chemical evolution sequence: simple organic molecules form first (monomers) → polymerisation into complex organics → coacervates (protobionts) self-assemble → primitive cells with metabolism and replication emerge (NCERT Class 12 Biology Chapter 6, page 111).
Why A is wrong: A is wrong because polymerisation requires monomers to already exist — you cannot polymerise before simple organic molecules are synthesised.
Why B is wrong: B is wrong because coacervates cannot form before monomers exist — organic molecule synthesis must precede aggregation.
Why C is wrong: C is wrong because coacervates form from polymers, not directly from monomers; polymerisation must come before coacervate assembly.
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How do you solve a Origin Life Panspermia question? A worked example
- 1
Given
A NEET question states: "Which of the following was NOT a component of the gas mixture used by Miller and Urey in their experiment?"
Options: (a) CH₄ (b) NH₃ (c) O₂ (d) H₂O vapour - 2
Required
Identify the gas absent from the Miller-Urey apparatus.
- 3
Concept
The Miller-Urey experiment simulated a reducing atmosphere. Reducing means no free oxygen. The gas mixture was CH₄ + NH₃ + H₂ + H₂O (NCERT Class 12 Biology Chapter 6, page 111).
- 4
Formula
No mathematical formula applies — this is a factual recall question testing knowledge of experimental conditions.
- 5
Substitution
Check each option against the known gas list:• CH₄ ✓ (present)• NH₃ ✓ (present)• O₂ ✗ (deliberately excluded)• H₂O vapour ✓ (present)
- 6
Calculation
No calculation needed. Direct elimination confirms O₂ is the only option not in the apparatus.
- 7
Final answer
(c) O₂ — free oxygen was absent because its oxidising nature would destroy nascent organic molecules.
- 8
Common trap
Students sometimes confuse H₂ (hydrogen gas, which WAS present) with O₂ (oxygen gas, which was NOT). The trap works because both are diatomic gases and students conflate "gases in the atmosphere" with "gases in Miller-Urey." Remember: reducing = no free O₂.
- 9
Similar NEET-style question
"In Miller's experiment, which of the following was used as a source of energy?"
(a) Solar radiation (b) Electric discharge (c) Cosmic rays (d) Nuclear radiation
Answer: (b) Electric discharge.
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What to remember before solving Origin Life Panspermia questions
More in Genetics and Evolution: 21 exam traps and mistakes · 4 formulas · 1 question pattern from its other lessons.
Origin Life Panspermia questions from past NEET papers
No question in our NEET 2020–2025 set targets this topic directly.
Sources
NCERT refs: Class 12 Biology Chapter 6, p.111
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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