Q.Describe the Miller-Urey experiment. What gases and energy source were used to simulate the conditions of primitive Earth in the sealed apparatus, and what was the key result obtained after a week of continuous sparking?

S. L. Miller's 1953 spark-discharge experiment simulated early-Earth atmospheric conditions and produced amino acids from simple inorganic gases, providing experimental support for the theory of chemical evolution of life (Oparin-Haldane hypothesis).

Miller assembled a closed apparatus containing a mixture of gases believed to represent the primitive Earth's reducing atmosphere (CH4, NH3, H2, and water vapour), and subjected it to an electric spark discharge (simulating lightning) for about a week. At the end, he found that about 15% of the carbon had been converted into simple organic compounds, including several amino acids - the building blocks of proteins. This was taken as strong experimental evidence that organic molecules necessary for life could have formed spontaneously from inorganic precursors under early-Earth conditions, i.e. supporting chemical evolution (abiogenesis), not spontaneous generation of complex life, biogenesis (life only from pre-existing life), or natural selection (which concerns differential survival/reproduction, a later stage of evolution).

Stanley Miller simulated the probable conditions of the primitive Earth using a mixture of CH4, NH3, H2, and water vapour, energised by an electric spark, to test the chemical origin of life.

In 1953, Stanley L. Miller, working with Harold Urey, designed a now-famous experiment to test the hypothesis (originally proposed by Oparin and Haldane) that simple organic molecules could have arisen spontaneously from inorganic matter under the conditions of the primitive Earth.

He created a closed flask apparatus containing a gaseous mixture simulating the reducing atmosphere then believed to have existed on early Earth: methane (CH4), ammonia (NH3), and hydrogen gas (H2), circulated over water (H2O) vapour, maintained at a temperature of about 800°C.

This mixture was continuously subjected to electric discharges (sparks, simulating lightning) for about a week. At the end of the experiment, Miller found that about 15% of the carbon (from methane) had been converted into simple organic compounds, including amino acids such as glycine, alanine, and aspartic acid — providing experimental support for the chemical (abiogenic) origin of life's building blocks.

The Miller-Urey experiment was conducted in 1953.

Stanley L. Miller, then a graduate student working under Harold Urey at the University of Chicago, conducted this famous experiment in 1953. He created laboratory conditions similar to those thought to exist on the primitive earth (a mixture of methane, ammonia, hydrogen and water vapour subjected to an electric spark), to test whether organic molecules essential for life could arise spontaneously from inorganic precursors.

Simple amino acids formed abiotically from the circulating gas mixture, condensing into the collected water.

After running the spark-discharge apparatus continuously for about a week, Miller analysed the liquid collected in the trap and found that about 15% of the carbon originally present as methane had been converted into simple organic compounds, including several amino acids (such as glycine and alanine, among others), which are the basic building blocks of proteins. This provided experimental support for the idea that the organic molecules necessary for life could have formed spontaneously on the early earth under similar conditions.

Stanley Miller's 1953 spark-discharge experiment used a mixture of methane, ammonia, hydrogen and water vapour to simulate the primitive Earth's reducing atmosphere.

Stanley L. Miller (with Harold Urey) built an experimental apparatus to test the Oparin-Haldane hypothesis of chemical evolution of life. The closed flask system contained a gas mixture of CH4 (methane), NH3 (ammonia), H2 (hydrogen) and water vapour (H2O) at about 800 degrees C, meant to simulate the reducing atmosphere thought to exist on early Earth.

Electric sparks (simulating lightning/UV radiation as an energy source) were discharged through this gas mixture for about a week. At the end of the experiment, about 15% of the carbon (from methane) had been converted into simple organic compounds, including amino acids such as glycine -- the building blocks of life. This provided experimental support for the idea that simple organic (and eventually biological) molecules could form spontaneously under early-Earth conditions.

Checking the options: only combination (c) -- H2, CH4, NH3, H2O -- correctly lists Miller's actual gas mixture (hydrogen, methane, ammonia and water vapour); the other options substitute incorrect gases (CO2, N2, or an invalid gas).