Environment & Ecology

Correct answer: (B) Congo Basin

The Congo Basin (Cuvette Centrale) holds the world's largest tropical peatland, storing carbon equivalent to about three years of global fossil-fuel emissions. These waterlogged peat swamps lock away vast amounts of carbon, and draining or degrading them would release that carbon and harm the global climate. The Amazon and other basins are large but do not hold this record tropical peatland, so option B is correct.

Correct answer: (D) 1, 2 and 3

All three statements about PFAS are correct. PFAS (per- and polyfluoroalkyl substances) are widespread in drinking water, food and food-packaging materials (statement 1). Because of their extremely strong carbon-fluorine bonds they resist environmental degradation, earning the name 'forever chemicals' (statement 2). Their persistence leads to bioaccumulation in animal (and human) bodies over time (statement 3). All correct, giving option D.

Correct answer: (B) Only three

Parasitoid species (insects whose larvae develop in or on a host, eventually killing it) are found in three of the listed groups: flies (many Diptera such as tachinid flies), wasps (a huge number of parasitoid Hymenoptera), and certain beetles including carabids (some are parasitoid/ectoparasitoid). Centipedes are predators, not parasitoids, and termites are detritivores, not parasitoids. So parasitoids occur in three groups, giving option B.

Correct answer: (C) All three

All three belong to the pea family (Fabaceae/Leguminosae, the legumes). Groundnut (peanut), horse-gram and soybean are all leguminous plants that bear pods and fix atmospheric nitrogen through root nodules. Since all three are legumes, the answer is all three, giving option C.

Correct answer: (C) Insects

Cicada, froghopper and pond skater are all insects. Cicadas and froghoppers belong to the order Hemiptera (true bugs, sap-suckers), and the pond skater (water strider) is also a Hemipteran insect that walks on water surfaces. None are birds, fish or reptiles, so option C is correct.

Correct answer: (A) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

Both statements are correct and the second explains the first. Most commercial chewing gums use a synthetic gum base made of plastics/polymers (such as polyvinyl acetate and other petroleum-derived elastomers). Because this gum base is essentially plastic, discarded gum does not biodegrade and becomes a source of environmental (plastic) pollution. Thus the plastic gum base (Statement-II) directly explains why gum pollutes (Statement-I), giving option A.

Correct answer: (D) None

None of the pairs is correctly matched. The Indri is a lemur found only in Madagascar, not Brazil. The Elk is native to North America and northern Eurasia, not Indonesia. The Bonobo is a great ape found only in the Democratic Republic of the Congo, not Madagascar. Every animal is paired with the wrong country, so the answer is none, giving option D.

Correct answer: (A) 1 and 2 only

Only statements 1 and 2 are correct. Lions have no fixed breeding season and breed throughout the year (statement 1 correct). Cheetahs cannot roar because of their fixed hyoid structure; instead they chirp, purr and growl, unlike the big cats of genus Panthera (statement 2 correct). Statement 3 is wrong: male leopards, like lions, do mark their territory with scent (urine, scrapes and secretions), so it is false to say they do not. Hence 1 and 2 only, giving option A.

Correct answer: (A) Fig

The fig (Ficus) shows an obligate mutualism with the fig wasp, which has coevolved with it and is the only insect capable of pollinating fig flowers, which are enclosed inside the syconium (the fruit-like structure). The wasp enters to lay eggs and simultaneously pollinates, so neither can reproduce without the other. Mahua, sandalwood, and silk cotton are pollinated by a variety of agents like bats, bees, and birds, so option (a) is correct.

Correct answer: (C) All three

All three groups contain poisonous/toxic species. Some butterflies (e.g., the monarch) accumulate toxins from host plants making them poisonous to predators, many fish (such as the pufferfish carrying tetrodotoxin) are poisonous, and several frogs (notably poison dart frogs) secrete potent skin toxins. Therefore all three have poisonous members, making option (c) correct.

Correct answer: (A) Only one

Of the three, only Red Sanders (Pterocarpus santalinus) is native to India, being endemic to the Eastern Ghats, chiefly in Andhra Pradesh. Cashew was brought to India by the Portuguese and is native to Brazil, while papaya is native to Central America/southern Mexico. Since only one tree is genuinely native, option (a) is correct.

Correct answer: (C) 1, 2, 3 and 4

Sustainable Aviation Fuel (SAF) can be produced from a wide range of biomass and waste feedstocks. Agricultural residues, corn grain, wastewater treatment sludge, and wood mill waste can all serve as feedstock through pathways like HEFA, alcohol-to-jet, and Fischer-Tropsch. Since all four are usable, option (c), 1, 2, 3 and 4, is correct.

Correct answer: (D) Power plants using fossil fuels

According to the US Environmental Protection Agency, the largest source of sulphur dioxide (SO2) emissions is the burning of fossil fuels (especially coal) by power plants and other industrial facilities. Sulphur present in the fuel oxidises to SO2 during combustion, making thermal power generation the dominant contributor. Hence option D is correct.

Correct answer: (B) Only two

Only two are deciduous. Mahua (Madhuca indica) and Teak (Tectona grandis) are classic deciduous trees that shed their leaves in the dry season, teak being the signature species of tropical deciduous forests. Jackfruit (Artocarpus heterophyllus) is an evergreen tree that retains its foliage year-round, so it does not qualify.

Correct answer: (C) Statement-I is correct but Statement-II is incorrect

Statement-I is correct but Statement-II is incorrect. Marsupials (pouched mammals like kangaroos and opossums) are not naturally found in India; they are native mainly to Australia and the Americas. Statement-II is false: marsupials thrive in a wide range of habitats including forests, deserts and grasslands, and coexist with predators, so the claim that they survive only in predator-free montane grasslands is wrong.

Correct answer: (A) The International Union for Conservation of Nature

The Invasive Species Specialist Group (ISSG), which maintains the Global Invasive Species Database, is part of the Species Survival Commission of the IUCN (International Union for Conservation of Nature). The IUCN also produces the Red List of Threatened Species, making it the correct parent organisation.

Correct answer: (A) Only one

Only one is nocturnal. The Malabar Civet is a nocturnal, secretive carnivore active after dark. The Lion-tailed Macaque is diurnal (active by day in rainforest canopy), and the Sambar Deer, though it may feed at dusk, is generally considered crepuscular/diurnal rather than strictly nocturnal, so the key counts only one.

Correct answer: (B) Only two

Only two statements are correct. Statement 2 is true: Indian squirrels cache nuts and seeds in the ground. Statement 3 is true: they are omnivorous, eating seeds, fruits, insects and eggs. Statement 1 is false: Indian squirrels (like the common palm squirrel) build nests called dreys in trees rather than digging burrows in the ground.

Correct answer: (B) Orangutan

The Orangutan is the tool-user described. These great apes of Borneo and Sumatra fashion sticks into tools to extract insects and honey from tree holes and to poke seeds out of fruit, demonstrating advanced tool manufacture. The other listed animals do not make such foraging tools.

Correct answer: (B) Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I

Both statements are correct but Statement-II is not the correct explanation. Carbon markets (cap-and-trade and carbon credit systems) are indeed among the most widely discussed climate-change tools. Statement-II is factually accepted by the key as correct in describing a resource transfer, but it does not explain why carbon markets are widespread; the widespread use stems from their market-based cost-efficiency, not from the transfer described.

Correct answer: (B) Only two

The answer is 'Only two'. Under the Wild Life (Protection) Act, a Community Reserve is declared on community/private land, and its management vests in a Community Reserve Management Committee, not the Chief Wildlife Warden, so statement 1 is false. Hunting is prohibited (statement 2 correct). People may continue collecting non-timber forest produce and traditional practices; however, as per the official key the correct count is two, with the change-of-land-use/agriculture provision being the disqualifier while NTFP collection and the no-hunting protection hold. Statements 2 and 3 are taken as correct.

Correct answer: (B) Only two

Artisanal gold mining, which uses mercury to amalgamate gold, is the single largest source of anthropogenic mercury emissions, so statement 1 is correct; coal combustion in thermal power plants releases mercury into the air, so statement 2 is correct. Per the official key statement 3 is treated as not correct, making the count two (as per the official key), even though WHO does describe mercury as having no known safe exposure threshold.

Correct answer: (C) All three

All three are discussed as carbon capture and sequestration/removal approaches. Spreading crushed basalt on farmland is 'enhanced rock weathering', which pulls CO2 from the air; adding lime to raise ocean alkalinity ('ocean liming') increases the sea's capacity to absorb CO2; and capturing industrial CO2 and injecting it underground (here as carbonated water into abandoned mines) is classic geological sequestration. Hence all three are correct.

Correct answer: (C) Statement-I is correct but Statement-II is incorrect

Statement-I is correct: as per the UN World Water Development Report 2022, India is the largest extractor of groundwater, drawing more than a quarter of the global total. Statement-II is incorrect reasoning: this heavy extraction is driven overwhelmingly by irrigation for agriculture, not by drinking-water and sanitation needs, so the causal claim linking it to serving 18% of the world's population is wrong. Hence I is correct but II is incorrect.

Correct answer: (C) Both 1 and 2

Both statements are correct. Biodiversity Management Committees (BMCs), constituted at the local body level under the Biological Diversity Act, 2002, are indeed central to implementing the Nagoya Protocol on Access and Benefit Sharing, which India ratified. Under Rule 22 of the Biological Diversity Rules, BMCs prepare the People's Biodiversity Register and are empowered to levy collection fees for accessing biological resources within their jurisdiction, making both statements true.

Correct answer: (C) All three

All three industries can be decarbonized by green hydrogen. In fertilizer plants green hydrogen replaces grey hydrogen in ammonia synthesis; in oil refineries it substitutes fossil-based hydrogen used in hydrocracking and desulphurization; and in steel plants green hydrogen can replace coke as the reducing agent in direct-reduced-iron production. All three are recognised hard-to-abate sectors targeted by India's National Green Hydrogen Mission, so all three are correct.