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 →
The acidification of oceans is increasing. Why is this phenomenon a cause of concern?
- The growth and survival of calcareous phytoplankton will be adversely affected.
- The growth and survival of coral reefs will be adversely affected.
- The survival of some animals that have phytoplanktonic larvae will be adversely affected.
- The cloud seeding and formation of clouds will be adversely affected.
Detailed Explanation:
✅ Statement 1 – Correct: Calcareous phytoplankton (like coccolithophores) need carbonate ions to build calcium carbonate shells; ocean acidification reduces these ions, impairing their calcification, growth, and survival.
✅ Statement 2 – Correct: Coral reefs are made of calcium carbonate; increased acidity lowers the saturation state, making it harder for corals to build skeletons and can cause reef dissolution.
✅ Statement 3 – Correct: Many marine invertebrates (mollusks, echinoderms) have phytoplanktonic larvae sensitive to seawater chemistry changes; acidification impairs their development and shell formation, increasing mortality.
❌ Statement 4 – Incorrect: While acidification may reduce dimethyl sulfide (DMS) production affecting cloud condensation nuclei, this is an indirect climatic feedback, not a primary direct concern for ocean ecosystems.
Consider the following:
- Black-necked crane
- Cheetah
- Flying squirrel
- Snow leopard
Which of the above are naturally found in India?
Detailed Explanation:
✅ Black-necked crane – Correct: Naturally found in Ladakh and Arunachal Pradesh (trans-Himalayan regions); migrates to India during winter.
❌ Cheetah – Incorrect: Declared extinct in India since 1952; the last three cheetahs were shot in Chhattisgarh (then part of Madhya Pradesh) in 1947. Recent reintroductions in Kuno National Park (2022) are not naturally found populations.
✅ Flying squirrel – Correct: Several species naturally occur in India, including Indian Giant Flying Squirrel (Western Ghats) and Red Giant Flying Squirrel (Northeast forests).
✅ Snow leopard – Correct: Found in high-altitude Himalayan and trans-Himalayan regions (Ladakh, Himachal Pradesh, Uttarakhand, Sikkim, Arunachal Pradesh) at elevations above 3,000–5,500 meters.
Consider the following kinds of organisms :
- Bat
- Bee
- Bird
Which of the above is/are pollinating agent/agents?
Detailed Explanation:
Pollinating agents are organisms that transfer pollen from male to female parts of flowers, enabling fertilization and seed production.
Bats (especially frugivorous and nectar-feeding species) pollinate tropical and desert plants while feeding on nectar, with pollen sticking to their fur.
Bees are the most efficient pollinators, collecting nectar and pollen for food and transferring pollen between flowers during foraging.
Birds (like hummingbirds, sunbirds, and honeyeaters) pollinate brightly colored, tubular flowers while feeding on nectar, with pollen adhering to their beaks and feathers.
All three organisms — bats, bees, and birds — are important pollinating agents in various ecosystems.
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What would happen if phytoplankton of an ocean is completely destroyed for some reason?
- The ocean as a carbon sink would be adversely affected.
- The food chains in the ocean would be adversely affected.
- The density of ocean water would drastically decrease.
Detailed Explanation:
✅ Statement 1 – Correct: Phytoplankton perform photosynthesis and absorb atmospheric CO₂, converting it into organic carbon through carbon sequestration. Their destruction would severely impair the ocean's role as a carbon sink.
✅ Statement 2 – Correct: Phytoplankton form the base of marine food chains, being the primary producers consumed by zooplankton and small fish, which support larger marine organisms. Their complete destruction would collapse oceanic food webs.
❌ Statement 3 – Incorrect: Ocean water density is determined by temperature and salinity, not by the presence of microscopic phytoplankton. Their removal would have negligible impact on water density.
Biomass gasification is considered to be one of the sustainable solutions to the power crisis in India. In this context, which of the following statements is/are correct?
- Coconut shells, groundnut shells and rice husk can be used in biomass gasification.
- The combustible gases generated from biomass gasification consist of hydrogen and carbon dioxide only.
- The combustible gases generated from biomass gasification can be used for direct heat generation but not in internal combustion engines.
Detailed Explanation:
✅ Statement 1 – Correct: Coconut shells, groundnut shells, and rice husk are excellent agricultural residues and biomass feedstock for gasification due to their high carbon content and low moisture.
❌ Statement 2 – Incorrect: The syngas (synthesis gas) from biomass gasification primarily contains carbon monoxide (CO), hydrogen (H₂), methane (CH₄), and carbon dioxide (CO₂), not just hydrogen and carbon dioxide.
❌ Statement 3 – Incorrect: Syngas from biomass gasification can be used for both direct heat generation and in internal combustion engines after proper cleaning and cooling to remove tar and particulates.
Vultures which used to be very common in the Indian countryside some years ago are rarely seen nowadays. This is attributed to
Detailed Explanation:
Diclofenac, a non-steroidal anti-inflammatory drug (NSAID) used by cattle owners to treat livestock, caused the catastrophic decline of vulture populations in India.
Vultures feeding on carcasses of diclofenac-treated cattle suffered acute kidney failure, leading to a 99% population crash of three species (White-rumped, Indian, and Slender-billed vultures) between the 1990s and early 2000s. India banned veterinary diclofenac in 2006.
The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere because it absorbs -
Detailed Explanation:
Carbon dioxide (CO₂) and other greenhouse gases absorb infrared radiation (heat) emitted by Earth's surface after it absorbs solar energy.
This trapped infrared radiation causes the greenhouse effect, gradually raising atmospheric temperature—not UV or all solar radiation, but specifically the long-wave infrared re-radiated from Earth.
Which one of the following groups of animals belongs to the category of endangered species?
Detailed Explanation:
Great Indian Bustard is Critically Endangered (IUCN), found in Rajasthan and Gujarat; Musk Deer is Endangered, hunted for musk pods in Himalayas; Red Panda is Endangered, native to eastern Himalayas; Asiatic Wild Ass (Khur) is Near Threatened (IUCN) but Schedule I species under Wildlife Protection Act, 1972.
Options 2, 3, and 4 are incorrect because they include Least Concern species: Cheetal, Blue Bull (Nilgai), Rhesus Monkey, and Hanuman Langur. Additionally, Saras Crane and Swamp Deer are Vulnerable, not Endangered.
Which of the following can be threats to the biodiversity of a geographical area?
- Global warming
- Fragmentation of habitat
- Invasion of alien species
- Promotion of vegetarianism
Detailed Explanation:
✅ Statement 1 – Correct: Global warming causes climate change, leading to habitat loss, altered precipitation patterns, and species extinction due to inability to adapt to rising temperatures.
✅ Statement 2 – Correct: Habitat fragmentation divides large habitats into smaller, isolated patches, reducing genetic diversity, disrupting migration corridors, and making populations more vulnerable to extinction.
✅ Statement 3 – Correct: Invasive alien species (e.g., Lantana camara, Water hyacinth) outcompete native species for resources, disrupt ecological balance, and cause local extinctions.
❌ Statement 4 – Incorrect: Promotion of vegetarianism reduces pressure on ecosystems by decreasing demand for livestock farming, which causes deforestation and habitat destruction—thus it benefits biodiversity, not threatens it.