Q30. Photochemical smog is principally a form of:
[WBCS Mains – Environmental Science (2020)]
(A) Air pollution
(B) Water pollution
(C) Soil pollution
(D) Biological nitrogen fixation
Answer: (A) Air pollution
Explanation: Photochemical smog develops in the atmosphere when sunlight drives reactions between traffic-related nitrogen oxides and organic vapours. Its secondary products include ozone and oxidants harmful to lungs and vegetation.
Q29. Savannas are best described as:
[WBCS Mains – Environmental Science (2020)]
(A) Closed tropical rainforests
(B) Bare desert scrub only
(C) Grasslands containing scattered trees
(D) Dense, closed-canopy woodlands
Answer: (C) Grasslands containing scattered trees
Explanation: Savannas are tropical or subtropical ecosystems dominated by grasses with trees dispersed across the landscape. Rainfall seasonality, grazing and fire help maintain their open structure rather than a closed forest canopy.
Q28. What is the microbial breakdown of pollutants in soil called?
[WBCS Mains – Environmental Science (2020)]
(A) Probiotics
(B) Bioremediation
(C) Biofortification
(D) None of these
Answer: (B) Bioremediation
Explanation: Bioremediation uses biological activity to transform harmful contaminants into less toxic products. Native or introduced microbes can digest certain organic pollutants; success depends on oxygen, moisture, nutrients and pollutant chemistry.
2019
Q27. Why were tiny plastic “microbeads” entering the environment a matter of concern?
[UPSC CSE Prelims GS Paper I (2019)]
(A) They harm marine ecosystems
(B) They are established causes of skin cancer in children
(C) Crop plants readily absorb them as nutrients
(D) They are frequently used to adulterate foods
Answer: (A) They harm marine ecosystems
Explanation: Microbeads are very small polymer particles used in some personal-care products. They can pass into waterways and be ingested by aquatic organisms, contributing to plastic pollution and potential ecological harm.
2018
Q26. Which leaf adaptations help desert plants reduce water loss?
1. Thick waxy leaves
2. Very small leaves
3. Leaves transformed into spines.
[UPSC CSE Prelims GS Paper I (2018)]
(A) 2 and 3 only
(B) 2 only
(C) 3 only
(D) 1, 2 and 3
Answer: (D) 1, 2 and 3
Explanation: A waxy cuticle can limit evaporation, while reduced leaf area decreases transpiration. Spines may replace leaves in xerophytes, with photosynthesis shifting to green stems. Such structural adaptations improve survival in dry environments.
Q25. In what context was the term “sixth mass extinction” used?
[UPSC CSE Prelims GS Paper I (2018)]
(A) Extensive monoculture and chemical-heavy commercial agriculture alone
(B) A future asteroid collision like the one associated with dinosaur extinction
(C) Widespread cultivation of genetically modified crops alone
(D) Human overuse of resources, habitat destruction, pollution and climate change
Answer: (D) Human overuse of resources, habitat destruction, pollution and climate change
Explanation: The sixth mass extinction refers to unusually rapid modern species losses linked chiefly to human pressures, including habitat conversion, overexploitation, pollution, invasive species and climate change. It is distinguished from past major extinction episodes in geological history.
2017
Q24. What does Biological Oxygen Demand (BOD) help assess?
[UPSC CSE Prelims GS Paper I (2017)]
(A) Oxygen in blood
(B) Oxygen in woodland air
(C) Organic pollution in aquatic systems
(D) Oxygen at high altitude
Answer: (C) Organic pollution in aquatic systems
Explanation: BOD measures oxygen consumed by microorganisms while breaking down biodegradable organic matter in water. Higher BOD generally signals greater organic pollution and potential oxygen depletion, which can threaten aquatic organisms.
Q23. What are advantages of bioremediation?
1. It enhances natural biodegradation.
2. Microbes completely destroy all heavy metals.
3. Engineered microbes may help remove particular pollutants.
[UPSC CSE Prelims GS Paper I (2017)]
(A) 1 only
(B) 2 and 3
(C) 1 and 3
(D) All three
Answer: (C) 1 and 3
Explanation: Bioremediation uses organisms to degrade or transform contaminants, and engineered strains may target specific substances. Heavy metals cannot be biodegraded into nothing; they may be immobilised, accumulated or altered in chemical form.
Q22. If butterfly populations collapse, what might follow?
1. Reduced pollination.
2. Necessarily higher crop fungal infection.
3. Declines in predators that feed on butterflies.
[UPSC CSE Prelims GS Paper I (2017)]
(A) 1 only
(B) 2 and 3
(C) 1 and 3
(D) All three
Answer: (C) 1 and 3
Explanation: Butterflies pollinate some flowering plants and supply prey to many spiders, wasps and birds. Their loss can disrupt both processes. A universal causal rise in fungal infections of cultivated plants cannot be inferred.
Q21. Which of the following is the State Bird of Jharkhand?
[JPSC CCE Prelims – GS Paper II (2017)]
(A) Pigeon
(B) Cuckoo
(C) Falcon
(D) Sparrow
Answer: (B) Cuckoo
Explanation: The Asian koel, commonly called the cuckoo in this examination, is Jharkhand’s state bird. Its distinctive call is widely familiar in eastern India; the other species listed are not the designated state bird.
