CUET UG Biology Booster Test 3 Origin of the Universe and Earth

The Big Bang theory begins with a singular massive explosion (II). As the universe expanded, it cooled down (IV). This cooling allowed subatomic particles to form the first atoms, specifically Hydrogen and Helium (I). Finally, these gas clouds condensed under gravitational influence to form galaxies (III).

Because stellar distances are measured in light years, the light we perceive on Earth has traveled for a significant duration before reaching our eyes. Therefore, we are observing the state of those stars as they existed when the light originally departed, effectively allowing us to "look back in time."

The term "speck" is used to highlight the relative insignificance of Earth's size when placed against the massive, incomprehensible scale of the universe and the galaxies it contains. It is a scaling metaphor, not a comment on formation time, gravity, or biological distribution.

Statement II is correct because early atmosphere chemistry relied on photolysis (UV-driven breakdown) of water to produce oxygen, which then reacted with methane and ammonia. Statement III is correct as condensation is temperature-dependent. Statement I is false because early Earth had a reducing atmosphere devoid of free oxygen; O2 was not released from the molten mass.

Option C is incorrect because oceans formed due to the condensation of water vapor after the planet cooled sufficiently. The chemical combination of oxygen and methane produced water and CO₂, but the oceans themselves are a result of water accumulation through rain after cooling, not a direct product of the chemical reaction prior to cooling.

1-iii: UV rays provide the energy to break water into Oxygen and Hydrogen. 2-ii: Free oxygen reacts with methane/ammonia to form CO2 and other stable compounds. 3-i: Hydrogen is light enough to escape the Earth's gravity. 4-iv: Condensing water vapor falls as rain to fill depressions, creating oceans.

Option C describes the Oparin-Haldane theory of Chemical Evolution (terrestrial origin). Panspermia argues for an extraterrestrial origin of life via "seeds" or spores. Therefore, believing in the terrestrial chemical origin is analytically incompatible with the Panspermia hypothesis.

Spontaneous Generation: Historically claimed life arises from decay (ii). Panspermia: Claims life came from space (iv). Chemical Evolution: Claims life formed from non-living organic molecules (i). Biogenesis: Demonstrated by Pasteur that life comes only from pre-existing life (iii).

Pasteur's experiment was definitive because he used a controlled setup (sterilized vs. open) to prove that microbes in the air were responsible for life in the flasks (I and III). Statement II is incorrect; science does not validate "vital force" as a requirement for life.

The experiment proved that even in the presence of organic nutrients (killed yeast), life did not emerge when the environment was sealed from outside contamination. This demonstrates that biological organization does not occur spontaneously from organic debris.

The Oparin-Haldane hypothesis focuses exclusively on the terrestrial origin of life through chemical evolution (inorganic to organic to life). Option B, which suggests life arrived via extraterrestrial spores, describes the Panspermia hypothesis, which is distinct from and competing with the Chemical Evolution theory.

1. The stage is set by the primitive atmosphere (II). 2. Inorganic constituents (water vapor, methane, ammonia) begin interacting (IV). 3. These interactions form diverse small organic molecules (I). 4. These small molecules polymerize into giant molecules like RNA and proteins (III).

Miller used electric discharge as a laboratory surrogate for the atmospheric electrical energy (lightning) and extreme heat (volcanic activity) that characterized the primitive Earth environment, providing the kinetic energy needed for chemical bond formation.

Miller's experiment is extremely sensitive: removing the energy source (A) stops the synthesis, adding oxygen (B) creates an oxidizing environment that prevents amino acid formation, and lowering the temperature (C) slows down the reaction kinetics required for synthesis. Therefore, all these factors would invalidate the experiment.

Miller's experiment proved that inorganic gases could produce organic monomers. Amino acids are the fundamental building blocks of proteins, which are essential for cellular structure and function, thereby providing the first real evidence that chemical evolution could lead to the components of life.

Finding organic molecules in meteorites serves as powerful indirect evidence that the chemical path from inorganic precursors to organic monomers is a fundamental, universal physical process, rather than a unique event occurring only under special Earth conditions.

The passage distinguishes these giant molecules from "standard chemical compounds" by their functional ability to replicate or reproduce their molecules—a hallmark of life, as opposed to inert, non-replicating chemistry.

In the context of the early evolution of life, "capsule" refers to a rudimentary, membrane-like (or isolated) system that allowed these giant molecules to concentrate and perform metabolic or replicative tasks, distinct from the surrounding environment.

The timeline explicitly shows a roughly one-billion-year duration between the first non-cellular forms (3 BYA) and the first cells (2 BYA). This indicates that the organizational process required to assemble self-replicating molecules into a stable, membrane-bound, cellular entity is a slow, complex evolutionary process.

Water is an essential solvent for the biochemical reactions required for life. Furthermore, since early Earth lacked a protective ozone layer and was subjected to intense radiation, the deep water or aquatic environments provided the necessary shielding for delicate, emerging cellular life.