UPSC 2013 Environment & Ecology PYQs with Answers

Mycorrhizae improve plant water/nutrient absorption, increase tolerance to stress such as drought and pH extremes, and can improve disease resistance. Hence they help rehabilitate degraded sites.

Desert plants reduce water loss through hard waxy leaves, tiny or absent leaves, and leaves modified into thorns. All three adaptations limit transpiration.

Gharial, leatherback turtle and swamp deer have all been treated as endangered/threatened fauna in India-related conservation contexts. Hence all three are included by the official key.

Fungi and bacteria are decomposers that break down dead organic matter. Viruses are not generally treated as decomposer organisms in food chains.

Photochemical smog forms in sunlight through reactions involving nitrogen oxides, ozone and secondary pollutants such as peroxyacetyl nitrate. It is characteristic of sunny urban atmospheres.

An ecological niche includes an organism's physical place, resource use and functional role in the community. Habitat refers mainly to where it lives.

Lion-tailed macaques are endemic to the Western Ghats and occur naturally in Kerala, Karnataka and Tamil Nadu. Andhra Pradesh is outside their natural range.

Animal urea adds nitrogen to soil after decomposition, and dead vegetation returns organic nitrogen. Burning coal releases nitrogen oxides to the atmosphere but is not a direct soil nitrogen-addition process here.

Nostoc is a cyanobacterium capable of nitrogen fixation and is used as a biofertilizer. Agaricus is a mushroom and Spirogyra is a green alga, not standard nitrogen-fixing biofertilizers.

Corbett is associated with Ramganga, Kaziranga with Brahmaputra/Diphlu-Mora Dhansiri systems rather than Manas, and Silent Valley with Kunthi/Bharathapuzha basin rather than Kaveri. None of the pairs is correct.

A food chain shows the sequence in which organisms feed on one another. It is not confined within a single species population and does not show numbers eaten; that is closer to ecological pyramids.

Acid rain is caused mainly by sulphur dioxide and nitrogen oxides emitted from combustion and industrial processes. These form sulphuric and nitric acids in the atmosphere.

E-waste from computers can release beryllium, cadmium, chromium, mercury and lead. Heptachlor and plutonium are not typical old-computer e-waste constituents.

Mangroves are highly productive coastal ecosystems, followed by grasslands and lakes; open oceans have low productivity per unit area despite large total production. Hence the decreasing order is mangroves, grasslands, lakes, oceans.

Grasslands are maintained by water limitation, seasonal drought and frequent fire/grazing, which prevent tree seedlings from replacing grasses in ecological succession.

Nokrek Biosphere Reserve is in the Garo Hills of Meghalaya. Loktak Lake is in Manipur, not the Barail Range, and Namdapha is in Arunachal Pradesh in the Patkai/eastern Himalayan region, not Dafla Hills.

Sea cow and sea lion are mammals. Sea horse is a fish, not a mammal.

Arsenic, fluoride and uranium contamination are documented in drinking water in parts of India. Sorbitol and formaldehyde are not typical groundwater drinking-water pollutants in this context.

Star tortoise, monitor lizard and pygmy hog are naturally found in India. Spider monkey is native to Central and South America, not India.