CUET UG Biology Booster Test 2 Origin of the Universe and Earth -

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CUET UG Biology Booster Test 2 Origin of the Universe and Earth

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Biology Booster Test 2 Origin of the Universe and Earth

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QUESTION 1 OF 20

Q1. Consider the following statements regarding the sequence of events after the Big Bang:
I. The universe expanded, causing the temperature to come down.
II. Hydrogen and Helium formed sometime later.
III. Gases condensed under gravitation to form the galaxies. Which of these statements correctly reflect the Big Bang theory's explanation?

Answer Review

1 Q1. Consider the following statements regarding the sequence of events after the Big Bang:
I. The universe expanded, causing the temperature to come down.
II. Hydrogen and Helium formed sometime later.
III. Gases condensed under gravitation to form the galaxies. Which of these statements correctly reflect the Big Bang theory's explanation?

A I and II only

B II and III only

C I and III only

D I, II, and III

💡 Short Explanation

The Big Bang started as a high-temperature singularity. Expansion led to cooling, allowing atoms (H and He) to form. Gravity then acted on these gases to create galactic structures.

✅ Correct Answer Explanation

According to the Big Bang theory, the universe underwent rapid expansion, which caused a drop in temperature. As the universe cooled, subatomic particles formed atoms, specifically Hydrogen and Helium. Eventually, gravitational forces caused clouds of these gases to condense, resulting in the formation of stars and galaxies. All three statements are accurate descriptions of this timeline.

❓ Why Other Options Are Incorrect

Options A, B, and C → These are incomplete because they exclude one of the three scientifically accurate statements provided.

🎯 Strategy

Used: Option Grouping

Application: Each statement describes a scientifically accepted phase of cosmic evolution, leading to the conclusion that all are correct.

Final Logic: The sequence (Expansion → Cooling → Atom Formation → Condensation) is accurately represented by all three statements.

🧠 Memory Trick

Cooling -> Atoms -> Gravity -> Galaxies.

📚 Class XII – Biology – Chapter: Evolution – Topic: Origin of Universe

2 Q2. Match the following terms to their correct contextual descriptions from the text:

List 1	List 2
1. Milky Way	i. Age of the universe
2. Speck	ii. Measurement of stellar distances
3. 13.8 billion years	iii. The galaxy containing our solar system
4. Light years	iv. The relative size of Earth compared to the universe

A 1-iii, 2-iv, 3-i, 4-ii

B 1-ii, 2-i, 3-iv, 4-iii

C 1-iii, 2-ii, 3-i, 4-iv

D 1-iv, 2-iii, 3-i, 4-ii

💡 Short Explanation

Milky Way is our galaxy. Earth is a 'speck' relative to the universe. 13.8 billion years is the age of the universe. Light years measure stellar distances.

✅ Correct Answer Explanation

This question tests the scale and context of cosmic terms: 1-iii: The Milky Way is the galaxy containing our solar system. 2-iv: Earth is described as a tiny 'speck' compared to the vast scale of the universe. 3-i: 13.8 billion years is the accepted estimate for the age of the universe. 4-ii: Light years are the standard unit used to measure astronomical distances.

❓ Why Other Options Are Incorrect

Options B, C, D → These options mismatch the terms with their definitions, creating scientifically incorrect pairings.

🎯 Strategy

Used: Substitution

Application: Match the most well-known term (e.g., 3-i: Age of universe) to narrow down the choices to A or C, then distinguish using the others.

Final Logic: Every term corresponds precisely to the provided definitions in option A.

🧠 Memory Trick

Age=13.8, Distance=Light years, Galaxy=Milky Way, Earth=Speck.

📚 Class XII – Biology – Chapter: Evolution – Topic: Universe Age and Scale

3 Q3. Which of the following conditions is NOT true regarding the early Earth (about 4.5 billion years back)?

A There was no atmosphere present initially.

B The surface was covered by water vapour, methane, carbon dioxide, and ammonia.

C A stable ozone layer existed from the exact moment of Earth's formation.

D Elements were released from a molten mass.

💡 Short Explanation

Ozone layer requires free oxygen (O₂). Early Earth had no free oxygen. Ozone layer formed much later.

✅ Correct Answer Explanation

The early Earth had a reducing atmosphere and lacked free oxygen (O₂). Since ozone (O₃) requires free oxygen to form, a stable ozone layer could not have existed at the time of Earth's formation. It developed only after photosynthetic organisms released oxygen into the atmosphere.

❓ Why Other Options Are Incorrect

Option A → Initially, Earth was a molten mass with no atmosphere; one developed as it cooled.
Option B → These were the gases released during the cooling phase.
Option D → Volcanic activity from the molten mass was indeed the source of early atmospheric gases.

🎯 Strategy

Used: Elimination

Application: Identify the "Ozone" claim as the outlier, given that ozone is dependent on the biological process of photosynthesis which had not yet occurred.

Final Logic: The absence of free oxygen on early Earth makes the existence of an ozone layer impossible.

🧠 Memory Trick

Ozone needs O₂; early Earth had no O₂.

📚 Class XII – Biology – Chapter: Evolution – Topic: Early Earth Conditions

4 Q4.Why did the lighter Hydrogen (H₂) gas escape from the early Earth's atmosphere?

A It was highly reactive with methane.

B It was formed from the splitting of water by UV rays and was light enough to escape gravity.

C It was consumed entirely by the first single-celled organisms.

D It was locked inside meteorite contents.

💡 Short Explanation

UV rays split water. Hydrogen is the lightest element. Earth's gravity could not retain it.

✅ Correct Answer Explanation

As the Earth cooled, UV rays from the sun split atmospheric water vapor into hydrogen and oxygen. Because hydrogen is the lightest gas, it could not be held by Earth's gravity and escaped into space, while the oxygen reacted with other gases.

❓ Why Other Options Are Incorrect

Option A → While hydrogen reacts with methane, its escape was primarily due to its low molecular weight and gravity.
Option C → Single-celled organisms did not exist during the initial atmospheric phase.
Option D → Meteorites are not the mechanism for atmospheric hydrogen loss.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Recognize the classic "splitting of water" explanation for the loss of hydrogen in primitive Earth models.

Final Logic: Physics dictates that lighter gases escape gravity more easily; UV splitting provided the source.

🧠 Memory Trick

UV splits Water -> Hydrogen is Light -> Bye-bye Hydrogen.

📚 Class XII – Biology – Chapter: Evolution – Topic: Early Earth Atmosphere

5 Q5. What chemical reaction allowed the early Earth to form liquid water, carbon dioxide, and other compounds after Hydrogen escaped?

A The spontaneous generation of organic matter.

B Oxygen combining with ammonia and methane.

C The breakdown of the ozone layer.

D The electric discharge hitting giant RNA molecules.

💡 Short Explanation

Hydrogen escape left behind oxygen. Oxygen reacted with existing gases. Result: Water and CO₂.

✅ Correct Answer Explanation

After hydrogen escaped, the oxygen released from the breakdown of water became available to react with other components in the atmosphere, specifically methane and ammonia, leading to the formation of liquid water and CO₂.

❓ Why Other Options Are Incorrect

Option A → Spontaneous generation is a debunked theory, not a chemical reaction.
Option C → The ozone layer did not exist yet to break down.
Option D → RNA molecules formed much later in the chemical evolution timeline.

🎯 Strategy

Used: Elimination

Application: Eliminate the non-chemical options (A, C, D) to arrive at the chemical interaction described in the text.

Final Logic: Oxidation of methane and ammonia is the chemical step that produced stable compounds like water and CO₂.

🧠 Memory Trick

O + Methane/Ammonia = Water + CO₂.

📚 Class XII – Biology – Chapter: Evolution – Topic: Pre-Biotic Chemistry

6 Q6. Arrange the sequence of atmospheric changes driven by solar radiation on primitive Earth:
I. Formation of water, CO₂, and the ozone layer.
II. UV rays break up water vapor into Hydrogen and Oxygen.
III. Oxygen combines with ammonia and methane.
IV. Lighter H₂ gas escapes.

A II → IV → III → I

B I → II → III → IV

C II → III → IV → I

D IV → II → I → III

💡 Short Explanation

UV breaks water (II). Light H₂ escapes (IV). Oxygen reacts with gases (III). Stable compounds and ozone form (I).

✅ Correct Answer Explanation

1. Solar UV rays split water vapor (II). 2. Hydrogen escapes due to being lightweight (IV). 3. The remaining Oxygen combines with ammonia and methane (III). 4. This results in the formation of water, CO₂, and eventually the ozone layer (I).

❓ Why Other Options Are Incorrect

Options B, C, D → These options disrupt the logical causal sequence of atmospheric chemistry.

🎯 Strategy

Used: Substitution

Application: Ensure the "splitting" (II) occurs before the "escape" (IV), which narrows it to A or C; then confirm the reaction (III) precedes the final product (I).

Final Logic: The logical flow of chemical synthesis dictates this specific order of operations.

🧠 Memory Trick

Split -> Escape -> React -> Form.

📚 Class XII – Biology – Chapter: Evolution – Topic: Atmospheric Evolution

7 Q7. If 'Panspermia' were entirely true, which of the following logical conclusions would follow?

A Life on Earth originated solely from deep ocean chemical reactions.

B Earth is the only planet capable of generating life from inorganic molecules.

C The basic units of life (spores) could be universally distributed across multiple planets.

D Life arose spontaneously from rotting mud.

💡 Short Explanation

Panspermia theory = Spores in space. Implication = Life is not limited to one planet.

✅ Correct Answer Explanation

The Panspermia hypothesis suggests that "spores" or "units of life" are present throughout the universe and were transferred to Earth. The logical conclusion is that if this is true, life is not unique to Earth but potentially distributed across the cosmos.

❓ Why Other Options Are Incorrect

Option A → This contradicts Panspermia, suggesting terrestrial origin.
Option B → Panspermia argues against Earth being the sole origin point.
Option D → This is the theory of spontaneous generation, not Panspermia.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Match the definition of "Panspermia" (seeds everywhere) to its logical consequence.

Final Logic: Universal distribution is the hallmark of the Panspermia hypothesis.

🧠 Memory Trick

Pan (All) + Spermia (Seeds) = Universal Life.

📚 Class XII – Biology – Chapter: Evolution – Topic: Theories of Origin

8 Q8. The theory of spontaneous generation fundamentally relied on the assumption that:

A Genetic mutations lead to new species.

B Complex organic molecules can form from inorganic gases.

C Living organisms can emerge directly from non-living, rotting matter like straw.

D Life was transported to Earth on meteorites.

💡 Short Explanation

Spontaneous Generation (Abiogenesis) = Life from Non-life. Classic examples = Straw, mud.

✅ Correct Answer Explanation

Spontaneous generation was an ancient, incorrect belief that living organisms could arise spontaneously from non-living, decaying organic matter. It was famously proposed that life could appear from things like straw, mud, and rotting material.

❓ Why Other Options Are Incorrect

Option A → This relates to the Theory of Evolution/Natural Selection.
Option B → This describes the Oparin-Haldane theory (Chemical Evolution).
Option D → This describes Panspermia.

🎯 Strategy

Used: Elimination

Application: Filter out modern scientific concepts to identify the archaic, incorrect assumption.

Final Logic: The definition of spontaneous generation is literally "life from nothing/non-living matter."

🧠 Memory Trick

Spontaneous = Sudden appearance from "junk."

📚 Class XII – Biology – Chapter: Evolution – Topic: Theories of Origin

9 Q9. Which of the following is NOT a conclusion drawn from Louis Pasteur's experiment?

A Life comes only from pre-existing life.

B Spontaneous generation theory is invalid.

C Killed yeast in a sealed, pre-sterilised flask does not give rise to new life.

D The first cellular form of life originated in a pre-sterilized environment.

💡 Short Explanation

Pasteur proved life doesn't arise now from dead matter. He did not explain how the first life began.

✅ Correct Answer Explanation

Pasteur's experiments successfully proved that life arises only from pre-existing life (Biogenesis) and debunked spontaneous generation. However, he specifically acknowledged that his experiment did not answer how the very first life form originated on Earth.

❓ Why Other Options Are Incorrect

Option A, B, C → These are direct, valid conclusions drawn from Pasteur's work.

🎯 Strategy

Used: Elimination

Application: Recognize the limitation of Pasteur's work; it proves life doesn't spontaneously form today, but remains silent on the origin of the first life.

Final Logic: Statement D is a scientific mystery that Pasteur's experiment did not resolve.

🧠 Memory Trick

Pasteur = Life from Life, NOT "How life started."

📚 Class XII – Biology – Chapter: Evolution – Topic: Life from Pre-existing Life

10 Q10. The significance of using a "pre-sterilised flask" in Pasteur's experiment was to:

A Increase the temperature to mimic primitive Earth.

B Ensure no living microorganisms were present inside the flask initially.

C Create a reducing atmosphere free of oxygen.

D Allow UV radiation to penetrate the glass.

💡 Short Explanation

Sterilization kills existing microbes. If life appears, it must be spontaneous. Life didn't appear → No spontaneous generation.

✅ Correct Answer Explanation

The purpose of pre-sterilizing the flask was to create a blank slate, ensuring no pre-existing microorganisms were inside. This way, if life did appear, it would have to be through spontaneous generation. Since no life appeared, it proved that life only comes from pre-existing life.

❓ Why Other Options Are Incorrect

Option A, C, D → These describe elements of the Miller-Urey experiment or primitive Earth, not the control variables of Pasteur's sterilization.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Connect the term "sterilization" to the medical/biological practice of removing all living contaminants.

Final Logic: A clean environment is a fundamental requirement for a negative control experiment.

🧠 Memory Trick

Sterile = Clean = No life inside.

📚 Class XII – Biology – Chapter: Evolution – Topic: Sterilization Principles

11 Q11. The hypothesis proposed by Oparin and Haldane shifted the scientific focus of the origin of life from:

A Spontaneous generation to Panspermia.

B Pre-existing life to pre-existing non-living organic molecules.

C Biogenesis to spontaneous generation.

D Marine environments to terrestrial environments.

💡 Short Explanation

Old theory: Biogenesis (life from life). New focus: Chemical evolution (inorganic → organic → life). Shift: Non-living organic molecules are the precursors.

✅ Correct Answer Explanation

Oparin and Haldane proposed that life did not appear suddenly from nothing, but through a series of chemical reactions where inorganic matter evolved into complex organic molecules. This shifted the paradigm from looking for immediate biological "seeds" to studying the pre-biotic chemical conditions of Earth.

❓ Why Other Options Are Incorrect

Option A → Panspermia is a different theory; Oparin-Haldane is about terrestrial chemical evolution.
Option C → Biogenesis (life from life) is correct; they did not promote spontaneous generation.
Option D → They specifically emphasized the "primordial soup" in oceans.

🎯 Strategy

Used: Elimination

Application: Identify the core shift introduced by Oparin-Haldane, which is the chemical evolution from non-living matter to biological building blocks.

Final Logic: The defining feature of their theory is "Chemical Evolution."

🧠 Memory Trick

Oparin-Haldane = Chemical Evolution = Non-living to Living.

📚 Class XII – Biology – Chapter: Evolution – Topic: Chemical Evolution

12 Q12. Which of the following was NOT considered a condition of the primitive Earth during chemical evolution?

A High temperature

B Volcanic storms

C Oxidising atmosphere

D Atmosphere containing CH₄ and NH₃

💡 Short Explanation

�� Primitive atmosphere = Reducing (no O₂). �� Oxidizing atmosphere = Modern (high O₂). �� Therefore, C is the incorrect condition.

✅ Correct Answer Explanation

The primitive Earth atmosphere was strongly reducing, meaning it lacked free oxygen. An oxidizing atmosphere requires free oxygen, which was only produced later by photosynthetic organisms. The other conditions—high heat, volcanic activity, and the presence of methane and ammonia—are all features of the early, reducing atmosphere.

❓ Why Other Options Are Incorrect

Options A, B, and D → These are all recognized characteristics of the primitive, reducing atmosphere that allowed chemical evolution to occur.

🎯 Strategy

Used: Extreme Word Filter

Application: "Oxidising" and "Reducing" are opposites; since early Earth was reducing, "Oxidising" must be the incorrect (not associated) term.

Final Logic: Free oxygen is a product of life, not a condition for the origin of life.

🧠 Memory Trick

Early Earth = RED (Reducing), not OXY (Oxidising).

📚 Class XII – Biology – Chapter: Evolution – Topic: Chemical Evolution Theory

📄 Passage

"In 1953, S.L. Miller, an American scientist created similar conditions in a laboratory scale. He created electric discharge in a closed flask containing CH4, H2, NH3 and water vapour at 800°C. He observed formation of amino acids. In similar experiments others observed, formation of sugars, nitrogen bases, pigment and fats."

Q13. What energy source did S.L. Miller use to simulate the high temperatures and volcanic storms of primitive Earth?

A UV radiation

B Electric discharge

C Radioactive decay

D Meteorite impacts

💡 Short Explanation

Miller simulation = Closed flask + Energy. Energy source = Electric discharge (to simulate lightning).

✅ Correct Answer Explanation

S.L. Miller utilized electric discharge in his experimental setup to provide the necessary energy for chemical reactions to occur, simulating the lightning and high-energy environmental conditions present on the primitive Earth.

❓ Why Other Options Are Incorrect

Option A → UV was a factor in nature, but not the energy source used in Miller's flask.

Option C & D → While these were present on early Earth, Miller did not use them in his laboratory simulation.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Directly retrieve the energy source from the provided passage: "He created electric discharge in a closed flask..."

Final Logic: The passage explicitly names electric discharge as the catalyst used.

🧠 Memory Trick

Miller = Electric Sparks = Energy.

📚 Class XII – Biology – Chapter: Evolution – Topic: Miller's Experiment

📄 Passage

Q14. Which specific combination of gases did Miller enclose in the flask to represent the primitive atmosphere?

A CO₂, O₂, NH₃, and water vapour

B CH₄, H₂, NH₃, and water vapour

C CH₄, O₂, N₂, and water vapour

D H₂, O₂, CH₄, and NH₃

💡 Short Explanation

�� Miller's gases = Methane, Hydrogen, Ammonia, and Water Vapour. �� Must NOT contain O₂ (oxidizing atmosphere).

✅ Correct Answer Explanation

Miller chose a mixture of methane (CH₄), hydrogen (H₂), ammonia (NH₃), and water vapour to simulate the reducing nature of the primitive atmosphere. The absence of oxygen (O₂) was critical to the design of his experiment.

❓ Why Other Options Are Incorrect

�� Options A, C, and D contain O₂, which is characteristic of an oxidizing atmosphere and would have prevented the synthesis of amino acids.

🎯 Strategy

Used: Elimination

Application: Eliminate all options containing O₂, as the primitive Earth had a reducing atmosphere with no free oxygen.

Final Logic: Option B is the only combination that matches the known "reducing" gas mixture.

🧠 Memory Trick

Miller's Mix: Methane, Hydrogen, Ammonia, Water.

📚 Class XII – Biology – Chapter: Evolution – Topic: Miller's Experiment

15 Q15. (Multiple Statement Type) Following Miller's discovery of amino acid formation, other scientists conducted similar experiments. Which of the following were observed to form in these subsequent experiments?
I. Sugars
II. Nitrogen bases
III. Pigments and fats

A I and II only

B II and III only

C I and III only

D I, II, and III

💡 Short Explanation

Miller's work opened the door to synthesizing other biomolecules. Later experiments produced sugars, bases, pigments, and fats.

✅ Correct Answer Explanation

Miller's experiment was a prototype. Subsequent laboratory experiments using similar conditions successfully synthesized sugars, nitrogen bases, pigments, and fats, confirming that many fundamental components of life can be synthesized abiotically.

❓ Why Other Options Are Incorrect

Options A, B, and C → These are incomplete, as all three listed items (sugars, nitrogen bases, pigments, and fats) were indeed observed.

🎯 Strategy

Used: Option Grouping

Application: The question lists classic biomolecules that represent the "next steps" in chemical evolution; if one is possible, the others often follow in these simulations.

Final Logic: All three are standard organic compounds produced in abiotic synthesis experiments.

🧠 Memory Trick

Later Experiments = All Biomolecules (Sugars, Bases, Fats).

📚 Class XII – Biology – Chapter: Evolution – Topic: Experimental Evidence

16 Q16.Match the scientific evidence/proposer to the corresponding concept:

List 1	List 2
1. S.L. Miller	i. Chemical evolution from inorganic constituents
2. Meteorite Analysis	ii. Similar organic processes occurring in space
3. Oparin and Haldane	iii. Life from pre-existing life
4. Louis Pasteur	iv. Laboratory synthesis of amino acids

A 1-iv, 2-ii, 3-i, 4-iii

B 1-ii, 2-iv, 3-iii, 4-i

C 1-iv, 2-i, 3-ii, 4-iii

D 1-i, 2-iii, 3-iv, 4-ii

💡 Short Explanation

1 (Miller) = Laboratory synthesis (iv). 2 (Meteorite) = Space processes (ii). 3 (Oparin-Haldane) = Chemical evolution theory (i). 4 (Pasteur) = Life from pre-existing life (iii).

✅ Correct Answer Explanation

1-iv: Miller provided experimental evidence for amino acid synthesis in the lab. 2-ii: Meteorite analysis showed organic synthesis occurs elsewhere in space. 3-i: Oparin and Haldane proposed the framework of chemical evolution. 4-iii: Pasteur demonstrated that life only arises from pre-existing life.

❓ Why Other Options Are Incorrect

Options B, C, D → These confuse the contributors and their specific scientific contributions.

🎯 Strategy

Used: Substitution

Application: Match Pasteur (4-iii) and Miller (1-iv) first; they are the most distinct.

Final Logic: A is the only option that correctly aligns each scientist/evidence with their defining contribution.

🧠 Memory Trick

Pasteur=Pre-existing, Miller=Monomers(Amino Acids).

📚 Class XII – Biology – Chapter: Evolution – Topic: Experimental Evidence

17 Q17. Which statement is NOT true regarding the first non-cellular forms of life?

A They could have originated 3 billion years back.

B They were giant molecules like RNA and Protein.

C They possessed a complex membranous envelope identical to modern eukaryotic cells.

D These capsules were likely capable of reproducing their molecules.

💡 Short Explanation

Non-cellular = No complex membranes. Eukaryotic cells = Complex, evolved much later.

✅ Correct Answer Explanation

The first non-cellular life forms (giant molecules like RNA and proteins) did not have complex membranous envelopes; those are features of advanced, cellular eukaryotic life. The non-cellular stage consisted of self-replicating molecules, not cells.

❓ Why Other Options Are Incorrect

Option A, B, D → These are all scientifically accepted descriptions of the non-cellular life stage.

🎯 Strategy

Used: Extreme Word Filter

Application: "Identical to modern eukaryotic cells" is an extreme exaggeration, as non-cellular life is a precursor to even the simplest cell, let alone complex eukaryotes.

Final Logic: Non-cellular molecules cannot, by definition, have eukaryotic cell membranes.

🧠 Memory Trick

Non-cellular ≠ Eukaryotic.

📚 Class XII – Biology – Chapter: Evolution – Topic: First Life Forms

18 Q18. The functional significance of the first giant RNA and protein molecules was that they:

A Immediately formed terrestrial plants.

B Acted as self-replicating metabolic capsules.

C Generated free oxygen through photosynthesis.

D Absorbed all UV radiation.

💡 Short Explanation

Early molecules = Self-replicating. Precursor to life = Basic metabolism.

✅ Correct Answer Explanation

The first giant RNA and protein molecules were significant because they developed the ability to replicate themselves and perform metabolic functions. This capacity for self-replication and metabolism is the prerequisite for the emergence of the first true living cells.

❓ Why Other Options Are Incorrect

Option A → Plants appeared billions of years later.
Option C → Photosynthesis required cellular complexity.
Option D → While they interacted with UV, they did not "absorb all" of it to protect the earth.

🎯 Strategy

Used: Elimination

Application: Eliminate options describing later evolutionary stages (plants, photosynthesis) to focus on the "first" functionality.

Final Logic: Self-replication is the fundamental property of life that giant molecules had to achieve.

🧠 Memory Trick

RNA/Protein = Self-Replication.

📚 Class XII – Biology – Chapter: Evolution – Topic: Giant RNA and Proteins

19 Q19. Arrange the evolutionary timeline milestones from oldest to most recent:
I. Earth's formation
II. First cellular form of life
III. First non-cellular form of life
IV. Origin of the Universe

A IV → I → III → II

B I → IV → II → III

C IV → I → II → III

D I → III → II → IV

💡 Short Explanation

Universe (13.8 BYA) → Earth (4.5 BYA) → Non-cellular (3 BYA) → Cellular (2 BYA).

✅ Correct Answer Explanation

The chronological order of these major milestones is: 1. Origin of the Universe (13.8 billion years ago) 2. Formation of Earth (4.5 billion years ago) 3. First non-cellular life (3 billion years ago) 4. First cellular life (2 billion years ago)

❓ Why Other Options Are Incorrect

Other options missequence the relative ages of these four major events.

🎯 Strategy

Used: Substitution

Application: Place the Universe (IV) and Earth (I) at the beginning, narrowing it to A or C; then distinguish based on Non-cellular (III) vs. Cellular (II).

Final Logic: The timeline of evolutionary history is fixed: Universe -> Earth -> Non-cellular -> Cellular.

🧠 Memory Trick

U -> E -> N -> C.

📚 Class XII – Biology – Chapter: Evolution – Topic: Cellular Emergence

20 Q20. The version of abiogenesis accepted by the majority posits that the first cellular life forms slowly arose from non-living molecules and were strictly confined to:

A The atmospheric ozone layer

B Volcanic ash deposits

C A water environment

D Underground caves

💡 Short Explanation

Life's origin = Aqueous. "Primordial soup" = Oceans/water.

✅ Correct Answer Explanation

The scientific consensus on abiogenesis places the origin of the first cells in a water environment (the primordial ocean). Water acts as the essential solvent for the chemical interactions required for the synthesis and stabilization of organic molecules and early biological structures.

❓ Why Other Options Are Incorrect

Option A, B, D → These environments either did not contain the necessary conditions or were not the primary site for the "primordial soup" reactions.

🎯 Strategy

Used: Elimination

Application: Use the biological principle that water is the universal solvent necessary for life.

Final Logic: A water environment is the only setting that provides the stability and chemistry required for early cellular life.

🧠 Memory Trick

Life needs Liquid = Water.

📚 Class XII – Biology – Chapter: Evolution – Topic: Water Environment Origin

CUET UG Biology Booster Test 2 Origin of the Universe and Earth

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