UPSC Prelims 2013 Environment questions: topic-wise weightage

Water limits and fire is correct (c). Grasslands get too little rainfall to support a full forest, and frequent fires, together with grazing, kill tree seedlings, while grasses regrow from their underground roots. Succession therefore stops at the grassland stage, a fire- or drought-maintained climax. (a) is wrong: insects and fungi affect both trees and grasses but do not stop succession. (b) is wrong: grasslands get plenty of sunlight, and their soils are often rich, as in the prairies and steppes. (d) fails because (c) is correct.

Notice India's grasslands: the terai and Kaziranga floodplain grasslands, the shola grasslands of the Nilgiris and the Banni grasslands of Kutch. Many are wrongly classed as 'wastelands' and planted with trees. Trap: (b) misreads open, sunny grasslands.

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Mangroves, grasslands, lakes, oceans is correct (c). Mangroves and estuaries are among the most productive ecosystems per unit area, thanks to nutrients from rivers and tides, warmth and sunlight. Grasslands come next, then lakes. The open ocean has the lowest productivity per unit area because surface waters are poor in nutrients, so it is often called a 'watery desert'. (a), (b) and (d) give the wrong order.

Notice the twist: because it is so vast, the ocean still produces about half of the world's total primary production. Other highly productive systems include coral reefs, swamps and tropical rainforests. Productivity is measured as net primary productivity in g/m²/year. Trap: total output and output per area are different measures.

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Statement 1 only is correct (a). A food chain shows the order in which organisms feed on each other, who eats whom, in sequence, such as grass → grasshopper → frog → snake → eagle (1). Statement 2 is wrong: a food chain links different species at different trophic levels, not members of one population. Statement 3 is wrong: a food chain shows no numbers; counts of organisms at each level are shown by ecological pyramids of number, biomass and energy. So (b), (c) and (d) fail.

Notice the related ideas: many interlinked chains form a food web. Only about 10% of energy passes to the next level (Lindeman's rule), so chains rarely exceed four or five links. Detritus food chains start from dead matter. Trap: chains show order, pyramids show quantity.

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Items 1 and 3 are correct (c). Animals excrete urea in urine (1), and dead vegetation decays (3); in both cases decomposers convert the nitrogen into ammonia and then nitrates in the soil (ammonification and nitrification). Item 2 is the doubt: burning coal releases nitrogen oxides into the air, and these can reach the soil through acid rain, so some argue it adds nitrogen indirectly; UPSC's key does not count it. So (a), (b) and (d) fail on the key.

Notice the full cycle: fixation by Rhizobium and lightning, nitrification by Nitrosomonas and Nitrobacter, and denitrification by Pseudomonas returning nitrogen to the air. The Haber–Bosch process makes most fertiliser nitrogen. Trap: emissions mainly add nitrogen to the atmosphere, not directly to soil.

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Ecological niche is correct (b). A habitat is an organism's address, the physical place it lives, while its niche is its profession: the space it occupies plus its functional role, what it eats, when it is active and how it affects others. (a) is wrong: an ecotone is a transition zone between two ecosystems, such as a forest edge or mangrove, often rich in species (edge effect). (c) is wrong: habitat is only the physical space. (d) is wrong: a home range is the area an animal regularly moves through.

Notice the related principle: Gause's competitive exclusion principle says two species cannot share exactly the same niche for long. The idea was developed by Joseph Grinnell and G.E. Hutchinson. Trap: 'habitat' and 'niche' are often used loosely as synonyms.

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Fungi and bacteria are correct (b). Fungi and bacteria break down dead plants, animals and wastes by secreting enzymes and absorbing the products, returning nutrients such as nitrogen and phosphorus to the soil. They are the decomposers of the food chain (2, 3). Item 1 is wrong: viruses cannot feed on dead matter; they have no metabolism of their own and multiply only inside living cells. So (a), (c) and (d) fail.

Notice the related terms: detritivores such as earthworms and termites physically break down litter before decomposers finish the job. The detritus food chain starts from dead matter and is important in forests. Without decomposers, nutrients would stay locked in dead bodies. Trap: viruses are microbes but not decomposers.

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Items 1, 2 and 3 are correct (a). The Indian star tortoise lives in dry scrub of peninsular India and Sri Lanka (1). Monitor lizards, such as the Bengal monitor, are widespread in India (2). The pygmy hog, the world's smallest and rarest wild pig, survives in Manas National Park and nearby grasslands in Assam (3). Item 4 is wrong: spider monkeys live only in the tropical forests of Central and South America. So (b), (c) and (d) fail.

Notice the conservation side: the star tortoise is heavily smuggled for the pet trade and was moved to CITES Appendix I in 2019. The Pygmy Hog Conservation Programme has bred and released hogs since 1996. India's only apes are the hoolock gibbons. Trap: 'monkey' sounds Indian but this one is American.

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Sea cow and sea lion are correct (b). The sea cow (dugong) and the sea lion are mammals: they breathe air with lungs, are warm-blooded and suckle their young (1, 3). The sea horse is a small fish, unusual because the male carries the eggs in a brood pouch (2). So (a), (c) and (d) fail.

Notice the Indian angle: the dugong lives in the Gulf of Mannar, Palk Bay and Andaman waters, and Tamil Nadu notified India's first Dugong Conservation Reserve in Palk Bay in 2022. It is the state animal of the Andaman and Nicobar Islands and is in Schedule I. Seahorses are threatened by the traditional medicine trade. Trap: 'sea' in the name says nothing about the class.

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Tamil Nadu, Kerala and Karnataka are correct (a). The lion-tailed macaque, an Endangered primate with a silver-white mane, lives only in the rainforests of the Western Ghats in Kerala, Tamil Nadu and Karnataka, in places such as Silent Valley, the Anamalai hills and the Sharavathi valley (1, 2, 3). Item 4 is wrong: it is not found in Andhra Pradesh. So (b), (c) and (d) fail.

Notice the threats: habitat broken up by tea, coffee and teak plantations; only about 4,000 remain in the wild. The Silent Valley campaign of the 1980s was partly fought to save it. It is in Schedule I of the Wildlife Act. Trap: the Eastern Ghats in Andhra look similar on a map but lack its rainforest.

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All three are correct per UPSC's key (c). The gharial, the leatherback turtle and the swamp deer (barasingha) are all threatened species protected under Schedule I of the Wildlife (Protection) Act, and UPSC treats all as endangered. In the current IUCN categories, the gharial is Critically Endangered, while the leatherback and swamp deer are Vulnerable, so 'endangered' is used loosely here. So (a), (b) and (d) fail on the key.

Notice the habitats: gharials survive mainly in the Chambal sanctuary; leatherbacks, the largest turtles, nest in the Andaman and Nicobar Islands (Galathea Bay, near the Great Nicobar project); the hard-ground barasingha lives in Kanha, Madhya Pradesh's state animal. Trap: legal 'endangered' and IUCN 'Endangered' are not the same.

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Pair 1 only is correct (a). Nokrek is the highest peak of the Garo Hills in Meghalaya, and the Nokrek Biosphere Reserve is known for wild citrus (Citrus indica) and red pandas (1). Pair 2 is wrong: Loktak Lake, with its floating phumdis and Keibul Lamjao, the only floating national park, home of the sangai deer, lies in the Manipur valley, not the Barail Range. Pair 3 is wrong: Namdapha is in eastern Arunachal near the Patkai range; the Dafla Hills are in western Arunachal. So (b), (c) and (d) fail.

Notice the related facts: Namdapha hosts four big cats (tiger, leopard, clouded leopard, snow leopard). Loktak is a Ramsar site on the Montreux Record. Trap: real places matched to wrong hills.

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Gram Sabha is correct (d). Under the Forest Rights Act, 2006, the Gram Sabha starts the process of determining individual and community forest rights. It receives claims, verifies them through its elected Forest Rights Committee, and passes a resolution, which then goes to the Sub-Divisional Level Committee and finally the District Level Committee for approval (Section 6). (a) is wrong: the Forest Department is only represented on the committees. (b) is wrong: the Collector chairs the district committee, which reviews, not initiates. (c) is wrong: revenue officers sit on the sub-divisional committee.

Notice the impact: the Niyamgiri case (2013) let Gram Sabhas decide on Vedanta's bauxite mining. Community Forest Resource rights let villages manage forests. The Ministry of Tribal Affairs is the nodal ministry. Trap: officials review claims, but the Gram Sabha begins them.

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None of the pairs is correct (d). Pair 1 is wrong: Corbett National Park, India's first (1936, as Hailey National Park), lies on the Ramganga, not the Ganga. Pair 2 is wrong: Kaziranga lies on the south bank of the Brahmaputra, with the Diphlu flowing through it; the Manas river flows through Manas National Park. Pair 3 is wrong: Silent Valley is drained by the Kunthipuzha, a tributary of the Bharathapuzha, not the Kaveri. So (a), (b) and (c) fail.

Notice the related facts: Kaziranga holds about two-thirds of the world's one-horned rhinos; Silent Valley was saved from a hydro project in the 1980s; Corbett was the first Project Tiger reserve in 1973. Trap: each park is paired with a famous but wrong river.

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Arsenic, fluoride and uranium are correct (c). Indian groundwater is contaminated with arsenic in the Ganga–Brahmaputra plains of West Bengal, Bihar, UP and Assam (1), fluoride in Rajasthan, Andhra Pradesh, Telangana and other states (3), and uranium in Punjab, Rajasthan and elsewhere (5). Item 2 is wrong: sorbitol is a sugar substitute. Item 4 is wrong: formaldehyde is an industrial chemical and preservative, not a known drinking-water contaminant here. So (a), (b) and (d) fail.

Notice the data: the CGWB's 2024 report found uranium above safe limits in parts of Punjab and nitrate in many districts. The Jal Jeevan Mission treats such water through community plants. Fluoride causes fluorosis, arsenic causes skin lesions and cancer. Trap: lab-sounding names are not always pollutants.

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Items 1, 2, 3, 5 and 6 are correct (b). Computers contain beryllium in connectors and motherboards (1), cadmium in batteries and chips (2), hexavalent chromium used against corrosion (3), mercury in switches and older flat screens (5), and lead in solder and old CRT glass (6). Item 4 is wrong: heptachlor is an organochlorine insecticide, not part of electronics. Item 7 is wrong: plutonium is a nuclear material and is not used in computers. So (a), (c) and (d) fail.

Notice India's rules: the E-Waste (Management) Rules, 2022 use Extended Producer Responsibility with tradable EPR certificates. India produced over 1.7 million tonnes of e-waste in 2023–24, and much is handled informally in places like Seelampur, Delhi. Trap: scary-sounding toxins are not all e-waste.

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Nitrous oxide and sulphur dioxide is correct (d), read as nitrogen oxides and sulphur dioxide. Sulphur dioxide, mainly from burning coal, and nitrogen oxides, from vehicles and power plants, react with water vapour and oxygen to form sulphuric and nitric acids, which fall as acid rain with pH below 5.6. (a) is wrong: nitrogen gas is inert, and CO₂ forms only weak carbonic acid. (b) is wrong: carbon monoxide does not cause acid rain. (c) is wrong: ozone is not an acid former.

Notice the effects: acid rain damages forests, acidifies lakes and erodes marble, as feared for the Taj Mahal from the Mathura refinery; the Taj Trapezium Zone was created to protect it. Flue gas desulphurisation cuts SO₂. Trap: the option's 'nitrous oxide' is loose wording for NOx.

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Option (a) is correct. Photochemical smog, the Los Angeles type, forms when sunlight acts on nitrogen oxides and hydrocarbons from vehicle exhaust. The reactions produce ozone and peroxyacetyl nitrate (PAN), which irritate eyes and lungs and damage plants; the brown haze includes NO₂. So the mixture of NO₂, O₃ and PAN in sunlight describes it best. (b) is wrong: carbon monoxide and oxygen are not its key components. (c) is wrong: it forms in warm, sunny conditions, not low temperatures. (d) is wrong: it peaks in the afternoon, not evening.

Notice the contrast: classical or London smog (1952) is sulphur dioxide plus smoke and fog in cold, damp weather. Delhi's winter smog mixes both types with stubble smoke. Trap: (a) lists products of the reaction, which UPSC accepts.

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