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 →
There is some concern regarding the nanoparticles of some chemical elements that are used by the industry in the manufacture of various products. Why?
- They can accumulate in the environment, and contaminate water and soil.
- They can enter food chains.
- They can trigger the production of free radicals.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Nanoparticles are extremely small (1-100 nm) and resistant to degradation, allowing them to persist and accumulate in soil and water bodies, contaminating the environment.
✅ Statement 2 – Correct: Due to their microscopic size, nanoparticles can be absorbed by plants and microorganisms, entering the food chain and undergoing biomagnification at higher trophic levels.
✅ Statement 3 – Correct: Certain nanoparticles can induce oxidative stress in cells by triggering the production of reactive oxygen species (ROS) or free radicals, which damage DNA, proteins, and cell membranes, potentially causing inflammation and cancer.
What is the significance of a practical approach to sugarcane production known as ‘Sustainable Sugarcane Initiative’?
- Seed cost is very low in this compared to the conventional method of cultivation.
- Drip irrigation can be practised very effectively in this.
- There is no application of chemical/ inorganic fertilizers at all in this.
- The scope for intercropping is more in this compared to the conventional method of cultivation.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: SSI uses single-bud chip setts raised in nurseries instead of traditional multi-budded setts, reducing seed requirement from ~3 tonnes/acre to just 75 kg, significantly lowering seed cost.
✅ Statement 2 – Correct: Wide spacing (4-5 feet between rows) in SSI enables highly effective use of drip irrigation, maintaining optimal moisture levels and reducing water consumption compared to flood irrigation.
❌ Statement 3 – Incorrect: SSI promotes judicious use of fertilizers and encourages organic inputs/bio-fertilizers but does not mandate complete exclusion of chemical/inorganic fertilizers; it focuses on efficient application.
✅ Statement 4 – Correct: Wider row spacing in SSI provides ample space and sunlight for intercropping with pulses, vegetables, or oilseeds, offering greater scope than conventional dense planting methods.
If you walk through the countryside, you are likely to see some birds stalking alongside the cattle to seize the insects, disturbed by their movement through grasses, Which of the following is/are such bird/birds?
- Painted Stork
- Common Myna
- Black-necked Crane
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Incorrect: Painted Storks are wading birds that feed on fish, frogs, and aquatic insects in shallow water bodies; they do not follow cattle through grasslands.
✅ Statement 2 – Correct: Common Mynas are insectivorous birds commonly seen following cattle and grazing animals to catch insects disturbed by their movement through grasses.
✅ Statement 3 – Incorrect: Black-necked Cranes are primarily herbivorous, feeding on grains, tubers, and aquatic plants; they are not known for insect-hunting behavior alongside cattle.
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With reference to ‘Global Environment Facility’, which of the following statements is/are correct
Detailed Explanation:
✅ Statement 1 – Correct: The Global Environment Facility (GEF) serves as the official financial mechanism for both the Convention on Biological Diversity (CBD) and the United Nations Framework Convention on Climate Change (UNFCCC), providing grants and funding for environmental projects in developing countries.
❌ Statement 2 – Incorrect: The GEF is a financial organization, not a scientific research body. Scientific research on environmental issues is conducted by organizations like IPCC (climate) and IPBES (biodiversity).
❌ Statement 3 – Incorrect: The GEF is an independent financial organization established in 1991, not an agency under the OECD. It operates as a partnership of 183 countries, international institutions, civil society organizations, and the private sector.
Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?
- Volcanic action
- Respiration
- Photosynthesis
- The decay of organic matter
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Volcanic eruptions release CO₂ trapped in the Earth's mantle and crust into the atmosphere.
✅ Statement 2 – Correct: Respiration by living organisms releases CO₂ as a byproduct of cellular metabolism.
❌ Statement 3 – Incorrect: Photosynthesis removes CO₂ from the atmosphere; plants use it to produce glucose and oxygen.
✅ Statement 4 – Correct: Decomposition of dead organic matter by decomposers releases CO₂ back into the atmosphere.
Brominated flame retardants are used in many household products like mattresses and upholstery. Why is there some concern about their use?
- They are highly resistant to degradation in the environment.
- They are able to accumulate in humans and animals.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Brominated flame retardants (BFRs) are persistent organic pollutants (POPs) that are highly resistant to environmental degradation, remaining in ecosystems for extended periods.
✅ Statement 2 – Correct: BFRs are lipophilic (fat-soluble) and undergo bioaccumulation in fatty tissues of humans and animals, leading to potential endocrine disruption and neurotoxicity.
Lichens, which are capable of initiating ecological succession even on a bare rock, are actually a symbiotic association of
Detailed Explanation:
Lichens are a symbiotic association of algae (or cyanobacteria) and fungi.
The fungal partner (mycobiont) provides shelter, water, and minerals, while the algal partner (phycobiont) performs photosynthesis to produce food. Lichens are pioneer species in ecological succession on bare rocks.
With reference to technologies for solar power production, consider the following statements:
- ‘Photovoltaics’ is a technology that generates electricity by direct conversion of light into electricity, while ‘Solar Thermal’ is a technology that utilizes the Sun’s rays to generate heat which is further used in the electricity generation process.
- Photovoltaics generates Alternating Current (AC), while Solar Thermal generates Direct Current (DC).
- India has a manufacturing base for Solar Thermal technology, but not for Photovoltaics.
Which of the statements given above is/are correct?
Detailed Explanation:
✅ Statement 1 – Correct: Photovoltaics (PV) directly converts light into electricity using semiconductor materials, while Solar Thermal uses concentrated sunlight to generate heat, which drives turbines for electricity generation.
❌ Statement 2 – Incorrect: Photovoltaic systems generate Direct Current (DC), which is converted to AC through inverters. Solar Thermal systems produce AC electricity directly through conventional turbine-generator systems.
❌ Statement 3 – Incorrect: India has a strong manufacturing base for Photovoltaics (companies like Adani Solar, Vikram Solar, Tata Power Solar), while Solar Thermal manufacturing is limited to small-scale applications like water heaters.
The scientific view is that the increase in global temperature should not exceed 2 °C above the pre-industrial level. If the global temperature increases beyond 3°C above the pre-industrial level, what can be its possible impact/impacts on the world?
- Terrestrial biosphere tends toward a net carbon source
- Widespread coral mortality will occur.
- All the global wetlands will permanently disappear.
- Cultivation of cereals will not be possible anywhere in the world.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Beyond 3°C warming, ecosystem tipping points like forest dieback and permafrost thaw cause the terrestrial biosphere to shift from carbon sink to carbon source, releasing more CO₂ than absorbed.
✅ Statement 2 – Correct: Coral reefs face 99% loss at 2°C warming; at 3°C, widespread coral mortality becomes catastrophic and irreversible globally.
❌ Statement 3 – Incorrect: The term "all wetlands" and "permanently disappear" is extreme; many wetlands would be severely degraded or lost, but complete global disappearance is scientifically implausible.
❌ Statement 4 – Incorrect: The term "anywhere in the world" is an overstatement; while cereal cultivation would face severe disruption and crop failures, high-latitude regions might still support limited production.
Consider the following statements:
- Animal Welfare Board of India is established under the Environment (Protection) Act, 1986.
- National Tiger Conservation Authority is a statutory body.
- National Ganga River Basin Authority is chaired by the Prime Minister.
Which of the statements given above is/ are correct?
Detailed Explanation:
❌ Statement 1 – Incorrect: Animal Welfare Board of India is established under the Prevention of Cruelty to Animals Act, 1960, not the Environment (Protection) Act, 1986.
✅ Statement 2 – Correct: National Tiger Conservation Authority (NTCA) is a statutory body constituted under the Wildlife (Protection) Amendment Act, 2006 for implementation of Project Tiger.
✅ Statement 3 – Correct: National Ganga River Basin Authority (NGRBA) was constituted under the Environment (Protection) Act, 1986 and chaired by the Prime Minister (replaced by National Ganga Council in 2016).
Other than poaching, what are the possible reasons for the decline in the population of Ganges River Dolphins?
- Construction of dams and barrages on rivers
- Increase in the population of crocodiles in rivers
- Getting trapped in fishing nets accidentally
- Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Dams and barrages fragment river habitats, restrict migration, isolate dolphin populations, and reduce prey availability.
❌ Statement 2 – Incorrect: Crocodile population increase is not a documented cause of dolphin decline; both species coexist in healthy river ecosystems.
✅ Statement 3 – Correct: Accidental entanglement in fishing nets (gillnets) is a major cause of mortality, leading to drowning of dolphins.
✅ Statement 4 – Correct: Agricultural chemical runoff pollutes rivers, contaminating prey species and causing bioaccumulation of toxins in dolphins.
Consider the following pairs
- Dampa Tiger Reserve: Mizoram
- Gumti Wildlife Sanctuary: Sikkim
- Saramati Peak: Nagaland
Which of the above pairs is /are correctly matched?
Detailed Explanation:
✅ Pair 1 – Correct: Dampa Tiger Reserve is located in Mizoram, notified as a wildlife sanctuary in 1985 and declared a Tiger Reserve in 1994. It is the largest wildlife sanctuary in Mizoram.
❌ Pair 2 – Incorrect: Gumti Wildlife Sanctuary is located in Tripura, not Sikkim. It was established in 1988 and is known for bison, sambar, and elephants.
✅ Pair 3 – Correct: Saramati Peak (3,826 m) is the highest peak in Nagaland, located on the Nagaland-Myanmar border in the Tuensang district.
Consider the following:
- Bats
- Bears
- Rodents
The phenomenon of hibernation can be observed in which of the above kinds of animals?
Detailed Explanation:
✅ Statement 1 – Correct: Bats undergo hibernation during winter months when insect prey becomes scarce, entering torpor to conserve energy.
✅ Statement 2 – Correct: Bears (brown bears, black bears, polar bears) are well-known hibernators, though they experience a lighter form of dormancy compared to true hibernators.
✅ Statement 3 – Correct: Many rodent species like groundhogs, chipmunks, ground squirrels are true hibernators with drastically reduced body temperature and metabolic rate.
Among the following organisms, which one does not belong to the class of the other three?
Detailed Explanation:
Crab belongs to class Crustacea, while Mite, Scorpion, and Spider all belong to class Arachnida.
Both are arthropods, but Crustaceans typically have two pairs of antennae and gills, whereas Arachnids have no antennae and possess eight legs.
Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss?
- Hard and waxy leaves
- Tiny leaves or no leaves
- Thorns instead of leaves
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Statement 1 – Correct: Desert plants develop hard, waxy cuticles on leaves to create a waterproof barrier that prevents transpiration and water loss.
✅ Statement 2 – Correct: Reduced leaf size or complete leaf loss minimizes surface area exposed to heat and sunlight, thereby reducing water evaporation.
✅ Statement 3 – Correct: Leaf modification into thorns/spines drastically reduces transpiring surface area while providing protection from herbivores in arid environments.