UPSC Prelims 2021 Question Paper

Detailed Explanation:

Answer: Option 3 — 1 and 3 Only

WaterCredit is an initiative of Water.org that uses microfinance tools to empower individuals to access water and sanitation solutions through small loans, enabling them to meet their needs without depending on subsidies. It is not a WHO or World Bank initiative.

✅ Statement 1 – Correct: WaterCredit applies microfinance principles to the water and sanitation sector, providing small loans to individuals and households for water and sanitation infrastructure.
❌ Statement 2 – Incorrect: WaterCredit is an initiative of Water.org, an international non-profit organization, not a global initiative launched under the aegis of WHO and World Bank.
✅ Statement 3 – Correct: The program aims to empower poor people to access water and sanitation through affordable financing, reducing their dependence on subsidies and enabling sustainable solutions.

Detailed Explanation:

Answer: Option 3 — 2 and 3 only

This question tests knowledge of labor laws and rights applicable to casual workers in India. Statement 1 is incorrect as EPF coverage is not automatic for all casual workers, while statements 2 and 3 are correct based on Supreme Court rulings and payment of wages regulations.

❌ Statement 1 – Incorrect: Not all casual workers are automatically entitled to Employees Provident Fund coverage. EPF coverage applies to establishments with 20 or more employees, and casual workers must have rendered continuous service (at least 240 days in a year or 206 days for 5-day week offices) to qualify for regularization and EPF benefits.

✅ Statement 2 – Correct: The Supreme Court has ruled that casual workers are entitled to regular working hours and overtime payment as they fall within the definition of 'employee' under various labor laws including the EPF Act, which defines employees broadly to include those engaged directly or indirectly in an establishment's work.

✅ Statement 3 – Correct: Under the Payment of Wages Act and related regulations, the government can issue notifications mandating that specific establishments or industries must pay wages only through bank accounts to ensure transparency and prevent exploitation.

📝 Short Notes: Rights of Casual Workers in India

Detailed Explanation:

Answer: Option 3 — 1 and 3 Only

In a pressure cooker, the cooking temperature depends on the internal pressure, which determines the boiling point of water. The area of the hole in the lid and the weight of the lid regulate how much pressure builds up inside the cooker, thereby controlling the cooking temperature. The flame temperature only affects the rate of heating, not the maximum temperature achieved.

✅ Statement 1 – Correct: The size of the hole in the lid regulates steam release; a larger hole allows more steam to escape, reducing internal pressure and thus lowering the cooking temperature.

❌ Statement 2 – Incorrect: The temperature of the flame affects only the rate of heating, not the final cooking temperature, which is determined by the internal pressure of the cooker.

✅ Statement 3 – Correct: A heavier weight on the lid requires higher internal pressure to lift it, allowing steam to escape only when higher pressure is reached, which increases the boiling point and thus the cooking temperature.

📝 Short Notes: Pressure Cooker Mechanism

• Principle: Pressure cookers work on the principle that increasing pressure raises the boiling point of water above 100°C.
• Normal Boiling Point: At atmospheric pressure (1 atm), water boils at 100°C.
• In Pressure Cooker: Pressure can reach 15 psi (about 2 atm), raising the boiling point to approximately 121°C.
• Pressure Regulation: The weight (regulator) on the vent controls the maximum pressure by allowing steam to escape when pressure exceeds a threshold.
• Vent Hole Size: The area of the vent hole determines how easily steam can escape, affecting pressure buildup.
• Cooking Time: Higher temperature due to increased pressure reduces cooking time significantly.
• Flame Role: The flame intensity affects how quickly the cooker reaches operating pressure, not the final cooking temperature.

Detailed Explanation:

Answer: Option 2 — 2 Only

Statement 1 is incorrect because adenoviruses have double-stranded DNA genomes, not single-stranded DNA. Retroviruses have single-stranded RNA genomes (not double-stranded DNA), which they reverse-transcribe into DNA using reverse transcriptase. Statement 2 is correct as adenoviruses are a common cause of the common cold, and AIDS is indeed caused by HIV, a retrovirus.

❌ Statement 1 – Incorrect: Adenoviruses have double-stranded DNA genomes; retroviruses have single-stranded RNA genomes, not double-stranded DNA.
✅ Statement 2 – Correct: The common cold can be caused by adenoviruses, and AIDS is caused by HIV, which is a retrovirus.

📝 Short Notes: Viral Genome Types

• DNA Viruses: Generally replicate in the nucleus using host cell machinery (exceptions: poxviruses replicate in cytoplasm)
• RNA Viruses: Most replicate in the cytoplasm; carry their own RNA polymerase
• Retroviruses: Unique in possessing reverse transcriptase enzyme that synthesizes DNA from RNA template
• Common Cold Causes: Rhinoviruses (most common), coronaviruses, adenoviruses, and others
• HIV Classification: Lentivirus genus of the Retroviridae family; targets CD4+ T cells

Detailed Explanation:

Answer: Option 4 — Speed of light is always same.

Astronomical distances are measured in light-years because the speed of light in a vacuum is a universal constant (approximately 299,792 km/s). This constant nature makes it a reliable and standardized unit for measuring the vast distances in space. A light-year represents the distance light travels in one year, providing a practical scale for cosmic distances.

❌ Statement A – Incorrect: Distances between stellar bodies do change due to orbital motion, stellar evolution, and galactic movements; this is not why light-years are used as a unit.

❌ Statement B – Incorrect: While gravity is fundamental, the gravitational effects of stellar bodies vary with mass and distance changes; this has no bearing on the choice of light-year as a distance unit.

❌ Statement C – Incorrect: Light does not always travel in a straight line; it bends around massive objects due to gravitational lensing, as predicted by Einstein's General Theory of Relativity.

✅ Statement D – Correct: The speed of light in a vacuum is constant at approximately 3 × 10⁸ m/s, making it an ideal standard for measuring astronomical distances.

📝 Short Notes: Astronomical Distance Measurements

• Light-Year: The distance light travels in one year in a vacuum (approximately 9.46 trillion kilometers or 5.88 trillion miles).
• Astronomical Unit (AU): The average distance from Earth to the Sun (approximately 150 million km); used for measuring distances within the solar system.
• Parsec: Another unit for astronomical distances, equal to about 3.26 light-years; commonly used by professional astronomers.
• Speed of Light (c): A fundamental physical constant equal to 299,792,458 meters per second in vacuum; remains constant regardless of the observer's motion or the source's motion.
• Gravitational Lensing: The bending of light around massive objects due to gravity, predicted by Einstein's General Theory of Relativity and observed around galaxies and black holes.

Detailed Explanation:

Answer: Option 4 — spread of viral diseases

ACE2 (Angiotensin-Converting Enzyme 2) is a protein receptor found on human cell surfaces that became widely discussed during the COVID-19 pandemic. The SARS-CoV-2 virus uses ACE2 as its primary entry point into human cells, binding to this receptor through its spike protein to infect cells in the lungs, heart, kidneys, and other organs.

📝 Short Notes: ACE2 Receptor

• Full Form: Angiotensin-Converting Enzyme 2
• Normal Function: ACE2 is an enzyme that plays a crucial role in regulating blood pressure and cardiovascular function by converting angiotensin II to angiotensin (1-7)
• Location: Found on cell surfaces in multiple organs including lungs (alveolar cells), heart, kidneys, intestines, and blood vessels
• Role in COVID-19: Acts as the cellular receptor that SARS-CoV-2 spike protein binds to for viral entry into cells
• Research Significance: Target for therapeutic interventions including soluble ACE2, monoclonal antibodies, and small molecule inhibitors to block viral entry
• Previous Connection: The original SARS-CoV virus (2003) also used ACE2 as its receptor, making it a known vulnerability in coronavirus infections

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Mitochondrial replacement therapy (MRT) is a reproductive technique designed to prevent the transmission of mitochondrial diseases from mother to child by replacing defective mitochondria with healthy donor mitochondria, either before or after in vitro fertilization. Mitochondrial DNA is inherited exclusively through the maternal line, as mitochondria in sperm are typically destroyed after fertilization, making it impossible for a child to inherit mitochondrial diseases from the father.

✅ Statement 1 – Correct: MRT can be performed either before fertilization (using maternal spindle transfer) or after fertilization (using pronuclear transfer) to prevent mitochondrial disease transmission.
✅ Statement 2 – Correct: Mitochondrial DNA is inherited entirely from the mother, as only the egg contributes mitochondria to the embryo.

📝 Short Notes: Mitochondrial Inheritance and Replacement Therapy

Detailed Explanation:

Answer: Option 3 — 1 and 3

This question compares traditional sodium lamps with modern LED lamps used in street lighting. Statement 1 correctly identifies that sodium lamps emit light omnidirectionally (360 degrees), while LEDs are directional, reducing light wastage. Statement 3 correctly notes that sodium lamps produce nearly monochromatic yellow light, whereas LEDs offer better color rendering and spectrum diversity.

✅ Statement 1 – Correct: Sodium lamps emit light in all directions (360 degrees), while LED lamps are directional and focus light where needed, improving efficiency.
❌ Statement 2 – Incorrect: LED lamps have a significantly longer lifespan (50,000-100,000 hours) compared to sodium lamps (15,000-24,000 hours).
✅ Statement 3 – Correct: Sodium lamps produce monochromatic yellow-orange light (narrow spectrum), while LED lamps offer a broad spectrum with better color rendering index (CRI) for street lighting.

📝 Short Notes: Street Lighting Technologies

Detailed Explanation:

Answer: Option 3 — Lemongrass

Lemongrass (also known as Citronella grass) is widely used in preparing natural mosquito repellents due to its strong citrus-like odor. The essential oil extracted from lemongrass contains citronella oil, which is highly effective in repelling mosquitoes. Studies have shown that lemongrass oil can repel or kill up to 95% of certain mosquito species, with effects lasting approximately 2-3 hours.

📝 Short Notes: Natural Mosquito Repellents

• Lemongrass (Cymbopogon): Contains citronella oil, the most commonly used natural mosquito repellent; effective against multiple mosquito species
• Mechanism: The strong citrus odor masks human scent and carbon dioxide, making it difficult for mosquitoes to locate their targets
• Citronella Oil: Extracted from lemongrass leaves; used in candles, sprays, lotions, and incense sticks
• Duration of Effect: Typically lasts 2-3 hours; requires reapplication for extended protection
• Other Natural Repellents: Neem oil, eucalyptus oil, lavender, basil, and marigold also possess mosquito-repelling properties
• Safety: Natural repellents are generally safer than chemical alternatives like DEET, with fewer side effects

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Recombinant vector vaccines utilize genetic engineering to insert pathogen genes into harmless carrier organisms (vectors), which then deliver these genes into human cells to produce antigens and trigger immunity. Both viruses (like Adenoviruses in Covishield) and bacteria (like attenuated Salmonella or BCG) can serve as vectors in these vaccines.

✅ Statement 1 – Correct: Genetic engineering is essential for developing recombinant vector vaccines, involving the insertion of pathogen antigen genes into a vector's genetic material.
✅ Statement 2 – Correct: Both bacteria (e.g., Salmonella, BCG) and viruses (e.g., Adenovirus, VSV) are used as vectors to deliver antigens.

📝 Short Notes: Recombinant Vector Vaccines

• Technology: Uses genetic engineering to insert genes encoding pathogen antigens into harmless viral or bacterial vectors
• Mechanism: Vectors deliver genetic material into host cells, which then produce antigens triggering immune response
• Viral Vectors: Adenoviruses (Covishield/Sputnik V), Vesicular Stomatitis Virus (Ebola vaccine - Ervebo), Modified Vaccinia Ankara (MVA)
• Bacterial Vectors: Attenuated Salmonella typhimurium, Mycobacterium bovis (BCG), Listeria monocytogenes strains
• Advantages: Strong cellular and humoral immunity, no live pathogen used, scalable production
• Examples: COVID-19 vaccines (AstraZeneca/Covishield, J&J, Sputnik V), Ebola vaccine (Ervebo), experimental TB and malaria vaccines

Detailed Explanation:

Answer: Option 2 — developing genetically modified crop plants.

Bollgard I and Bollgard II are biotechnology products developed for creating genetically modified (GM) cotton plants with insect resistance. These technologies use genes from Bacillus thuringiensis (Bt) bacteria to produce insecticidal proteins that protect cotton plants from bollworm and other lepidopteran pests, thereby reducing the need for chemical pesticides.

📝 Short Notes: Bt Cotton Technologies

Detailed Explanation:

Answer: Option 1 — it is dipolar in nature

Water is known as the "universal solvent" because of its dipolar (polar) nature. Water molecules have a bent structure with partial positive charges on hydrogen atoms and a partial negative charge on the oxygen atom, creating a dipole. This polarity enables water molecules to surround and interact with ions and other polar molecules through electrostatic attraction, effectively separating and dissolving them. The dipolar nature is the fundamental reason why water can dissolve more substances than any other liquid.

📝 Short Notes: Properties of Water as a Solvent

• Dipolar/Polar Nature: Water has a bent molecular structure (H-O-H angle ~104.5°) with oxygen being more electronegative, creating partial charges (δ+ on H, δ- on O).
• Universal Solvent: Water dissolves ionic compounds (like salts) by surrounding ions with water molecules (hydration) and polar covalent compounds through hydrogen bonding.
• Hydrogen Bonding: The polar nature allows water molecules to form hydrogen bonds with each other and with solute particles, facilitating dissolution.
• High Dielectric Constant: Water has a high dielectric constant (~80), which reduces the electrostatic attraction between dissolved ions, keeping them separated in solution.
• Not Related to Solvent Properties: Good heat conductor, high specific heat, and being an oxide of hydrogen are properties of water but not the primary reasons for its exceptional solvent capabilities.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three groups—cnidarians, fungi, and protozoa—have species capable of establishing symbiotic relationships with other organisms. This demonstrates the widespread occurrence of symbiosis across different taxonomic groups in nature.

✅ Statement 1 – Correct: Cnidarians like corals form symbiotic relationships with zooxanthellae (photosynthetic algae), which is essential for coral reef ecosystems.
✅ Statement 2 – Correct: Fungi form diverse symbiotic associations including mycorrhizae with plant roots and lichens with algae or cyanobacteria.
✅ Statement 3 – Correct: Protozoa establish symbiotic relationships, such as those living in termite guts that help digest cellulose.

📝 Short Notes: Symbiotic Relationships in Different Organisms

• Mutualism: Both organisms benefit from the relationship
• Symbiosis: Close and long-term biological interaction between different species
• Zooxanthellae: Single-celled dinoflagellates crucial for coral bleaching studies
• Ecological importance: Symbiotic relationships are fundamental to ecosystem functioning and biodiversity

Detailed Explanation:

Answer: Option 3 — 2 and 3

Lichens and mosses are uniquely adapted to survive on bare surfaces without soil. Lichens, being symbiotic associations of fungi and algae/cyanobacteria, can colonize rocks and tree bark by absorbing nutrients directly from air and rain. Mosses, though non-vascular plants, possess specialized structures that enable them to absorb water and nutrients from their immediate environment without requiring soil.

Analysis of Organisms:
1. Fern – Cannot survive without soil: Ferns are vascular plants requiring soil to anchor their roots and absorb water through their well-developed root systems.

2. Lichen – ✅ Can survive without soil: Lichens are symbiotic organisms (fungus + algae/cyanobacteria) that obtain nutrients directly from air and precipitation, thriving on rocks, bark, and other bare surfaces.

3. Moss – ✅ Can survive without soil: Mosses are bryophytes (non-vascular plants) with rhizoids that can attach to bare surfaces and absorb water and minerals directly from the environment.

4. Mushroom – Cannot survive without soil: Mushrooms are fungal fruiting bodies that require organic substrates (decaying matter, soil rich in nutrients) for the mycelium to grow and produce fruiting structures.

📝 Short Notes: Organisms Surviving Without Soil

• Lichens are pioneer species in ecological succession, colonizing bare rocks and weathering them into soil over time.
• Lichens as bioindicators: Highly sensitive to air pollutants like SO₂, NOₓ, and heavy metals; absence indicates poor air quality.
• Mosses reproduce via spores and require moisture for fertilization but can survive desiccation in dry conditions.
• Bryophytes (mosses, liverworts, hornworts) lack vascular tissues (xylem and phloem) but can thrive in moist, shaded environments on various substrates.
• Ferns are more advanced than mosses, having vascular tissues, but still require moist conditions and soil for optimal growth.

Detailed Explanation:

Answer: Option 1 — 1 and 2 Only

Bacteria and fungi can be cultured in artificial/synthetic media as they possess complete cellular machinery for independent growth and reproduction. Viruses, being obligate intracellular parasites, lack cellular machinery and can only replicate inside living host cells, making them incapable of growth in synthetic media.

✅ Statement 1 (Bacteria) – Correct: Bacteria can be cultured in various artificial media like nutrient agar, nutrient broth, and other specialized media as they are self-sufficient organisms with complete metabolic machinery.

✅ Statement 2 (Fungi) – Correct: Fungi can be cultured in artificial media such as Potato Dextrose Agar (PDA), Sabouraud Dextrose Agar, and Czapek Dox Agar, as they can independently utilize nutrients for growth.

❌ Statement 3 (Virus) – Incorrect: Viruses cannot be cultured in artificial/synthetic media as they are acellular and require living host cells (embryonated eggs, cell cultures, or living organisms) for replication.

📝 Short Notes: Microorganism Cultivation Methods

• Artificial Media: Chemically defined or complex media prepared in laboratory without living cells
• Bacterial Culture: Can grow on solid (agar plates) or liquid (broth) media at specific temperature and pH
• Fungal Culture: Require slightly acidic pH and longer incubation periods compared to bacteria
• Viral Culture: Requires tissue culture, embryonated chicken eggs, or experimental animals
• Key Difference: Viruses are acellular and depend entirely on host cell ribosomes, enzymes, and nucleotides for replication

Detailed Explanation:

Answer: Option 4 — Officers of the Indian National Army

Shah Nawaz Khan, Prem Kumar Sehgal, and Gurbaksh Singh Dhillon were senior officers of the Indian National Army (INA), also known as the Azad Hind Fauj, led by Netaji Subhas Chandra Bose. They are famously remembered for the historic Red Fort Trials (INA Trials) of 1945-46, where they were court-martialed by the British for 'waging war against the King-Emperor'. The trials sparked massive nationalist demonstrations across India and became a turning point in India's freedom struggle, with the Indian National Congress organizing an INA Defence Committee comprising legal luminaries like Bhulabhai Desai, Tej Bahadur Sapru, and Jawaharlal Nehru to defend them.

📝 Short Notes: Red Fort Trials and INA

• Indian National Army (INA): Formed in 1942 by Netaji Subhas Chandra Bose from Indian prisoners of war and expatriates in Southeast Asia to fight British rule.
• Red Fort Trials (November 1945 - May 1946): Court-martial of INA officers at Red Fort, Delhi. The first trial featured three officers representing different communities - Shah Nawaz Khan (Muslim), Prem Kumar Sehgal (Hindu), and Gurbaksh Singh Dhillon (Sikh).
• Charges: Waging war against the King-Emperor, murder, and abetment of murder.
• Public Response: Massive demonstrations, strikes, and protests across India; united Hindus, Muslims, and Sikhs in nationalist fervor.
• Defence Committee: Led by Bhulabhai Desai; included Tej Bahadur Sapru, Jawaharlal Nehru, and Kailash Nath Katju.
• Outcome: All three were sentenced to deportation for life, but the Commander-in-Chief remitted the sentences due to public pressure. The trials accelerated British decision to leave India.
• Legacy: The INA trials demonstrated that the British could no longer rely on Indian armed forces' loyalty and significantly contributed to the independence movement.

Detailed Explanation:

Answer: Option 1 — The Quit India Resolution was adopted by the AICC.

On 8th August 1942, the All India Congress Committee (AICC) passed the historic Quit India Resolution at Bombay, launching the Quit India Movement under Mahatma Gandhi's leadership. This marked a decisive phase in India's freedom struggle, demanding immediate British withdrawal from India.

✅ Option 1 – Correct: The Quit India Resolution was indeed adopted by the AICC on 8th August 1942 at Bombay (now Mumbai).
❌ Option 2 – Incorrect: The expansion of the Viceroy's Executive Council was part of the August Offer of 1940, not related to 8th August 1942.
❌ Option 3 – Incorrect: Congress ministries resigned in seven provinces in October-November 1939 following the outbreak of World War II, not in 1942.
❌ Option 4 – Incorrect: Cripps Mission proposing Dominion Status occurred in March 1942, not on 8th August 1942.

📝 Short Notes: Quit India Movement (1942)

Detailed Explanation:

Answer: Option 1 — 1 Only

This question tests knowledge of the early English East India Company factories established in the first quarter of the 17th century (1600-1625). Of the three locations mentioned, only Broach had an operational English factory during this period.

✅ Statement 1 – Correct: Broach (Bharuch, Gujarat) was established as an English factory in 1616-1617, soon after the establishment of the Surat factory (1613), making it one of the early trading posts on the western coast.

❌ Statement 2 – Incorrect: Chicacole (Srikakulam, Andhra Pradesh) was not an English factory in the first quarter of the 17th century; the English presence on the eastern coast was primarily at Masulipatnam (established 1611).

❌ Statement 3 – Incorrect: Trichinopoly (Tiruchirappalli, Tamil Nadu) did not have an English factory in the early 17th century; it gained strategic importance only during the mid-18th century Carnatic Wars between the English and French.

📝 Short Notes: Early English East India Company Factories (17th Century)

Detailed Explanation:

Answer: Option 3 — Rabindranath Tagore translated the National Anthem from Bengali to English here.

Madanapalle in Andhra Pradesh holds a unique place in Indian history as the location where Rabindranath Tagore translated 'Jana Gana Mana' from Bengali to English. During his stay at the Besant Theosophical College in Madanapalle in February 1919, Tagore rendered the translation titled "The Morning Song of India."

❌ Option 1 – Incorrect: Pingali Venkayya designed the tricolour Indian National Flag but presented it to Mahatma Gandhi at the INC session in Bezwada (now Vijayawada), not Madanapalle.

❌ Option 2 – Incorrect: Pattabhi Sitaramaiah was a prominent leader in Andhra Pradesh and served as Congress President, but he did not lead the Quit India Movement from Madanapalle.

✅ Option 3 – Correct: Rabindranath Tagore translated Jana Gana Mana from Bengali to English as "The Morning Song of India" during his stay at Madanapalle in 1919.

❌ Option 4 – Incorrect: The Theosophical Society was founded in New York (1875) and moved its international headquarters to Adyar, Chennai (1882), not Madanapalle.

📝 Short Notes: Jana Gana Mana and National Symbols

• Composition: Jana Gana Mana was originally composed in Bengali by Rabindranath Tagore in 1911.
• First Performance: It was first sung at the Calcutta Session of the Indian National Congress on December 27, 1911.
• English Translation: Tagore translated it to English as "The Morning Song of India" at Madanapalle, Andhra Pradesh in February 1919.
• Adoption as National Anthem: The Constituent Assembly adopted Jana Gana Mana as India's National Anthem on January 24, 1950.
• Duration: The full version has five stanzas; the official playing time of the shortened version is approximately 52 seconds.
• Nobel Prize: Rabindranath Tagore was awarded the Nobel Prize in Literature in 1913, becoming the first non-European to receive this honor.

Detailed Explanation:

Answer: Option 3 — Ishwar Chandra Vidyasagar

Ishwar Chandra Vidyasagar served as Secretary of the Hindu Female School (established in 1849), which was later renamed Bethune Female School in honor of its founder J.E.D. Bethune. Vidyasagar played a crucial role in promoting women's education in Bengal and was instrumental in the administration and development of this pioneering institution for female higher education in India.

📝 Short Notes: Social Reformers and Women's Education