Test: Origin of Life (NCERT) - NEET MCQ

According to Oparin-Haldane theory, life originated through bio-chemical processes of atoms that combined to form molecules. Molecules in turn reacted to produce inorganic and organic compounds. Organic compounds interacted to produce all types of macromolecules which organised to form the first form of life or cells.

Topic in NCERT: Origin of life

Line in NCERT: "oparin of russia and haldane of england proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. rna, protein, etc.) and that formation of life was preceded by chemical evolution, i.e., formation of diverse organic molecules from inorganic constituents."

Stanley Miller in 1953 took an air tight apparatus and circulated four gases - CH₄, NH₃, H₂ and water vapour through it. He passed electrical discharges from electrodes at 800^∘C. Then he passed the mixture through a condenser He performed this experiment continuously in this way for a week and analysed the composition of the liquid inside the apparatus. He found a large number of simple organic compounds including some amino acids such as alanine, glycine and aspartic acid. Miller, thus, proved that organic compounds were basis of life.

Topic in NCERT: Evolution of life forms - a theory

Line in NCERT: "he created electric discharge in a closed flask containing ch4, h2, nh3 and water vapour at 800°c."

Organisms have evolved from simpler forms to complex form. Hence the order of the events are genes first, then heterotrophic prokaryotes, then autotrophic prokaryotes, then eukaryotes and then animals.

Topic in NCERT: Evolution of life forms - a theory

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Since many simpler and lower animals are aquatic and marine, and as the cells and body fluids of all animals contain salts, it is inferred that life originated in ocean (water).

Topic in NCERT: Origin of life

Line in NCERT: "the first cellular form of life did not possibly originate till about 2000 million years ago. these were probably single-cells. all life forms were in water environment only."

• Louis Pasteur by careful experimentation demonstrated that life comes only from pre existing life.
• He showed that in pre sterilised flasks, life did not come from killed yeast while in another flask open to air, new living organisms arose from ‘killed yeast’.
• Spontaneous generation theory was dismissed once and for all.

Topic in NCERT: Origin of life

Line in NCERT: "experimentation demonstrated that life comes only from pre-existing life."

Louis Pasteur's experiment, which involved pre-sterilized flasks to show that no life arose from "killed yeast" unless exposed to air, helped to dismiss the theory of spontaneous generation, proving that life comes only from pre-existing life.

Topic in NCERT: Origin of life

Line in NCERT: "louis pasteur by careful experimentation demonstrated that life comes only from pre-existing life. he showed that in pre-sterilised flasks, life did not come from killed yeast while in another flask open to air, new living organisms arose from ‘killed yeast'. spontaneous generation theory was dismissed once and for all."

The Big Bang theory suggests that the universe originated from a singular, immense explosion, leading to its ongoing expansion and cooling, eventually forming stars, galaxies, and other celestial bodies.

Topic in NCERT: Origin of universe

Line in NCERT: "the big bang theory attempts to explain to us the origin of universe. it talks of a singular huge explosion unimaginable in physical terms."

Oparin of Russia and Haldane of England proposed that the formation of life was preceded by chemical evolution, which involved the formation of diverse organic molecules from inorganic constituents under Earth's early conditions.

Topic in NCERT: Origin of life

Line in NCERT: "oparin of russia and haldane of england proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. rna, protein, etc.) and that formation of life was preceded by chemical evolution, i.e., formation of diverse organic molecules from inorganic constituents."

In 1953, S.L. Miller conducted an experiment where he created conditions similar to early Earth with a mixture of gases and electrical discharges. This resulted in the formation of amino acids, supporting the idea of chemical evolution as a precursor to the origin of life.

Topic in NCERT: Origin of life

Line in NCERT: "he created electric discharge in a closed flask containing ch4, h2, nh3 and water vapour at 800°c. he observed formation of amino acids."

The formation of the ozone layer was crucial in early Earth's history as it helped to shield the surface from harmful ultraviolet rays from the sun, thereby protecting the nascent forms of life and allowing biological processes to occur more safely.

Topic in NCERT: Origin of life

Line in NCERT: "the ozone layer was formed."