UPSC CSE Prelims
Environment & Ecology Previous Year Questions (PYQs)
Solved Previous Year Questions (PYQs) for Environment & Ecology in UPSC CSE Prelims in English & Hindi Medium.
Chapter Breakdown: Scroll →
Which of the following can be found as pollutants in the drinking water in some parts of India?
- Arsenic
- Sorbitol
- Fluoride
- Formaldehyde
- Uranium
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Arsenic (1) – Correct: Found in groundwater of West Bengal, Bihar, Uttar Pradesh, Assam, Jharkhand due to natural leaching from arsenic-bearing rocks; causes arsenicosis and skin lesions.
❌ Sorbitol (2) – Incorrect: A sugar alcohol used as artificial sweetener and humectant; not a naturally occurring groundwater pollutant in India.
✅ Fluoride (3) – Correct: Endemic in Rajasthan, Andhra Pradesh, Tamil Nadu, Gujarat, Haryana and other states; causes dental and skeletal fluorosis from geological sources.
❌ Formaldehyde (4) – Incorrect: An industrial chemical and disinfectant; not a common groundwater contaminant in Indian drinking water systems.
✅ Uranium (5) – Correct: Detected in groundwater of Punjab, Rajasthan, Haryana and parts of southern India; leaches from uranium-bearing granitic rocks.
In the grasslands, trees do not replace the grasses as a part of an ecological succession because of
Detailed Explanation:
Grasslands maintain themselves as climax communities due to two primary limiting factors: water scarcity and periodic fires.
Grasses have meristematic tissue at the base (not tips), allowing rapid regrowth after fire, while tree seedlings die in fires. Additionally, low annual precipitation (25-75 cm) and thin, dry soil prevent tree establishment, maintaining grasslands in a sub-climax stage.
With reference to food chains in ecosystems, consider the following statements :
- A food chain illustrates the order in which a chain of organisms feeds upon each other.
- Food chains are found within the populations of a species.
- A food chain illustrates the numbers of each organism which are eaten by others.
Which of the statements given above is/are correct?
Detailed Explanation:
✅ Statement 1 – Correct: A food chain illustrates the linear sequence in which organisms feed upon each other, showing the order of energy flow from producers → primary consumers → secondary consumers → tertiary consumers.
❌ Statement 2 – Incorrect: Food chains operate between different species, not within populations of a single species; they represent inter-species feeding relationships across different trophic levels.
❌ Statement 3 – Incorrect: A food chain shows only the feeding relationship and direction of energy flow, not the numbers or biomass of organisms; ecological pyramids illustrate numerical or biomass relationships.
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Mycorrhizal Biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to -
- Resist drought and increase absorptive area
- Tolerate extremes of pH
- Resist disease infestation
Select the correct answer using the codes given below:
Detailed Explanation:
✅ Statement 1 – Correct: Mycorrhizal fungi form symbiotic associations with plant roots, greatly increasing the effective absorptive surface area (fungal hyphae extend beyond roots) and improving water uptake, enabling plants to resist drought stress.
✅ Statement 2 – Correct: Mycorrhizae help plants tolerate extreme pH conditions (both acidic and alkaline soils) by facilitating nutrient acquisition even when pH levels reduce nutrient availability.
✅ Statement 3 – Correct: Mycorrhizae provide bioprotection against disease infestation by competing with soil-borne pathogens, producing antimicrobial compounds, and enhancing plant immune responses.
Consider the following animals:
- Sea cow
- Sea horse
- Sea lion
Which of the above is/are mammal/mammals?
Detailed Explanation:
Sea Cow (Dugong): A herbivorous marine mammal found in coastal waters of the Indian and Pacific Oceans; classified under class Mammalia.
Sea Horse: A carnivorous fish (not a mammal) belonging to class Osteichthyes; found in shallow tropical and temperate waters.
Sea Lion: A carnivorous marine mammal of family Otariidae; breeds on Pacific and Atlantic coasts; classified under class Mammalia.
Therefore, only Sea Cow (1) and Sea Lion (3) are mammals.
How does the National Biodiversity Authority (NBA) help in protecting Indian agriculture?
- NBA checks the biopiracy and protects indigenous and traditional genetic resources.
- NBA directly monitors and supervises the scientific research on genetic modification of crop plants.
- Application for Intellectual Property Rights related to genetic/biological resources cannot be made without the approval of the NBA.
Detailed Explanation:
✅ Statement 1 – Correct: NBA checks biopiracy and protects indigenous and traditional genetic resources under the Biological Diversity Act, 2002.
❌ Statement 2 – Incorrect: NBA does not directly monitor genetic modification research on crops; this is done by GEAC (Genetic Engineering Appraisal Committee) under the Ministry of Environment, Forest and Climate Change.
✅ Statement 3 – Correct: IPR applications related to biological resources require prior approval from NBA as per Section 6 of the Biological Diversity Act.
Government of India encourages the cultivation of ‘sea buckthorn’. What is the importance of this plant?
- It helps in controlling soil erosion and preventing desertification.
- It is a rich source of biodiesel.
- It has nutritional value and is well-adapted to live in cold areas of high altitudes.
- Its timber is of great commercial value.
Detailed Explanation:
✅ Statement 1 – Correct: Sea buckthorn is a soil-binding plant with extensive root systems that effectively control soil erosion and prevent desertification, particularly in fragile Himalayan ecosystems.
❌ Statement 2 – Incorrect: Sea buckthorn is not a source of biodiesel; it is cultivated for its berries, leaves, and medicinal/nutritional products, not biofuel production.
✅ Statement 3 – Correct: The plant has high nutritional value with berries rich in vitamins C, E, carotenoids, and omega fatty acids, and thrives in cold, high-altitude regions like Ladakh and Spiti (-40°C to +40°C tolerance).
❌ Statement 4 – Incorrect: Sea buckthorn is a shrub, not a timber tree; its commercial value lies in fruits, cosmetics, pharmaceuticals, not timber.
In which one among the following categories of protected areas in India are local people not allowed to collect and use the biomass?
Detailed Explanation:
National Parks in India prohibit local people from collecting or using biomass as per the Wildlife Protection Act, 1972.
Biosphere Reserves (buffer & transition zones), Wildlife Sanctuaries (with Chief Wildlife Warden's permission), and Ramsar Wetlands (site-specific regulations) allow regulated biomass collection by local communities under certain conditions.
What is the difference between the antelopes Oryx and Chiru?
Detailed Explanation:
✅ Statement 1 – Correct: Oryx is a genus of four large antelope species adapted to hot and arid areas of Africa and Arabia, whereas Chiru (Tibetan antelope) is adapted to steppes and semi-desert areas of cold high mountains on the Tibetan Plateau.
❌ Statement 2 – Incorrect: Oryx has horns (not antlers) but is not primarily poached for them; Chiru is poached for its fine underfur (shahtoosh), not musk.
❌ Statement 3 – Incorrect: Oryx does not exist in western India naturally (found in Africa/Arabia); Chiru is found in Ladakh and high-altitude regions, not north-east India.
Consider the following areas:
- Bandipur
- Bhitarkanika
- Manas
- Sunderbans
Which of the above are Tiger Reserves?
Detailed Explanation:
Bandipur (Karnataka) – Declared a Tiger Reserve in 1973 under Project Tiger; one of India's first nine tiger reserves.
Bhitarkanika (Odisha) – A wetland and mangrove ecosystem known for saltwater crocodiles and bird diversity; NOT a Tiger Reserve.
Manas (Assam) – A Tiger Reserve, National Park, UNESCO World Heritage Site, Elephant Reserve, and Biosphere Reserve.
Sunderbans (West Bengal) – A Tiger Reserve famous for Royal Bengal Tigers adapted to mangrove habitat; also a UNESCO World Heritage Site.
Therefore, 1, 3 and 4 only are Tiger Reserves.
If the National Water Mission is properly and completely implemented, how will it impact the country?
- Part of the water needs of urban areas will be met through recycling of wastewater.
- The water requirements of coastal cities with inadequate alternative sources of water will be met by adopting appropriate technologies that allow for the use of ocean water.
- All the rivers of Himalayan origin will be linked to the rivers of peninsular India.
- The expenses incurred by farmers for digging bore-wells and for installing motors and pump sets to draw groundwater will be completely reimbursed by the Government.
Select the correct answer using the codes given below:
Detailed Explanation:
✅ Statement 1 – Correct: The National Water Mission (NWM) explicitly includes urban water recycling and reuse as a key strategy to meet part of the water needs of urban areas and reduce dependency on freshwater sources.
✅ Statement 2 – Correct: The NWM promotes adoption of desalination technologies for coastal cities facing water scarcity, particularly where alternative freshwater sources are inadequate.
❌ Statement 3 – Incorrect: The interlinking of rivers is a separate project under the National Perspective Plan, not part of the NWM's mandate, which focuses on water conservation and efficient use.
❌ Statement 4 – Incorrect: The NWM emphasizes sustainable groundwater management and promotes efficiency, but does not include financial reimbursement schemes for farmers' bore-well and pump-set expenses.
Lead, ingested or inhaled is a health hazard. After the addition of lead to petrol has been banned, what still are the sources of lead poisoning?
- Smelting units
- Pens and pencils
- Paints
- Hair oils and cosmetics
Detailed Explanation:
✅ Statement 1 – Correct: Smelting units release lead particles into air and soil during ore processing, making them a major source of environmental lead contamination.
❌ Statement 2 – Incorrect: Pencils contain graphite (carbon) and clay, not lead; the term "lead" is a historical misnomer.
✅ Statement 3 – Correct: Lead-based paints remain a significant hazard as deteriorating paint releases lead dust and chips that can be inhaled or ingested.
❌ Statement 4 – Incorrect: While some traditional cosmetics (surma/kohl) may contain lead, standard hair oils and modern cosmetics are not primary sources of lead poisoning.
With reference to the wetlands of India, consider the following statements :
- The country’s total geographical area under the category of wetlands is recorded more in Gujarat as compared to other States.
- In India, the total geographical area of coastal wetlands is larger than that of inland wetlands.
Which of the statements given above is/are correct?
Detailed Explanation:
✅ Statement 1 – Correct: Gujarat has the largest geographical area under wetlands in India, accounting for approximately 17.56% of the country's total wetland area, followed by West Bengal, Andhra Pradesh, and Uttar Pradesh.
❌ Statement 2 – Incorrect: Inland wetlands account for 69% of India's total wetland area, while coastal wetlands constitute only 27%, making inland wetlands significantly larger than coastal wetlands.
The Millennium Ecosystem Assessment describes the following major categories of ecosystem services: provisioning, supporting, regulating, preserving, and cultural. Which one of the following is a supporting service?
Detailed Explanation:
Millennium Ecosystem Assessment (2005) classifies ecosystem services into four categories: Provisioning, Regulating, Supporting, and Cultural.
Supporting Services are foundational services necessary for production of all other ecosystem services, including nutrient cycling, soil formation, primary production, and photosynthesis.
Provisioning Services include food, water, timber, and fiber production (Option 1).
Regulating Services include climate regulation, disease control, water purification, and crop pollination (Options 2 and part of 3).
Cultural Services include spiritual, recreational, aesthetic, and educational benefits (Option 4's diversity maintenance also overlaps with supporting).
Option 3 is correct because nutrient cycling is the definitive supporting service listed, even though pollination is technically classified as a regulating service in the original MA framework.
Consider the following statements: Chlorofluorocarbons, known as ozone-depleting substances, are used
- in the production of plastic foams
- in the production of tubeless tyres
- in cleaning certain electronic components
- as pressurizing agents in aerosol cans
Which of the statements given above is/are correct?
Detailed Explanation:
✅ Statement 1 – Correct: CFCs were widely used as blowing agents in the production of plastic foams (polystyrene, polyurethane) for insulation and packaging.
❌ Statement 2 – Incorrect: Tubeless tyres are manufactured through vulcanization using sulfur; CFCs have no role in tyre production.
✅ Statement 3 – Correct: CFC-113 was extensively used as a solvent for cleaning electronic components and circuit boards due to its non-flammable, residue-free properties.
✅ Statement 4 – Correct: CFCs served as propellants/pressurizing agents in aerosol cans (hairsprays, deodorants) before being phased out under the Montreal Protocol.