UPSC 2025. With reference to the planet Earth, consider the following statements:

1. Rain forests produce more oxygen than that produced by oceans. — WRONG — the ocean makes at least as much
2. Marine phytoplankton and photosynthetic bacteria produce about 50% of world’s oxygen. — CORRECT — about half
3. Well-oxygenated surface water contains several folds higher oxygen than that in atmospheric air. — WRONG — it is the other way round

Answer: (b) II only

Remember: Ocean phytoplankton ≈ half of Earth’s oxygen. Air holds ~30× more O₂ than water.

UPSC 2010. A pesticide which is a chlorinated hydrocarbon is sprayed on a food crop. The food chain is: Food crop – Rat – Snake – Hawk. In this food chain, the highest concentration of the pesticide would accumulate in which one of the following?

Answer: (d) Hawk

Remember: Fat-soluble + non-degradable + not excreted = biomagnification. Top predator = highest concentration.

UPSC 2022. Which of the following are nitrogen-fixing plants?

1. Alfalfa — YES — a legume
2. Amaranth — NO
3. Chick pea — YES — a legume
4. Clover — YES — a legume
5. Purslane (Kulfa) — NO
6. Spinach — NO

Answer: (a) 1, 3 and 4 only

Remember: Pea family = nitrogen-fixer: alfalfa, chickpea, clover. Leafy greens (amaranth, purslane, spinach) are not.

UPSC 2015. In a particular region in India, the local people train the roots of living trees into robust bridges across the streams. As the time passes, these bridges become stronger. These unique ‘living root bridges’ are found in

Answer: (a) Meghalaya

Remember: Living root bridges = Meghalaya (Khasi–Jaintia hills) · Ficus elastica · stronger with age.

UPSC 2026. Which of the following best explain(s) the rationale for protecting mangrove ecosystems in the context of climate resilience?

1. Mangroves reduce tidal energy and store freshwater, making them ideal sites for paddy cultivation in saline estuarine belts. — WRONG — no freshwater store, and paddy means clearing them
2. Their salt-sensitive roots filter seawater, making mangroves key to converting coastal land into freshwater aquaculture zones. — WRONG — the roots are salt-TOLERANT
3. By withstanding tidal surges and offering biomass resources, mangroves function both as natural bio-shields and livelihood bases for rural communities. — CORRECT — shield + livelihood

Answer: (d) 3 only

Remember: Mangroves = bio-shield + livelihood. Salt-tolerant, not salt-sensitive. Paddy or aquaculture conversion destroys them.

UPSC 2024. Which of the following organisms perform waggle dance for others of their kin to indicate the direction and the distance to a source of their food?

Answer: (c) Honeybees

Remember: Waggle dance = honeybee. Angle to vertical = angle to the sun; duration = distance. Von Frisch, Nobel 1973.

UPSC 2025. Regarding Peacock tarantula (Gooty tarantula), consider the following statements:

1. It is an omnivorous crustacean. — WRONG — it is a spider (arachnid), and it hunts
2. Its natural habitat in India is only limited to some forest areas. — CORRECT — a tiny range
3. In its natural habitat, it is an arboreal species. — CORRECT — it lives in trees

Answer: (d) II and III

Remember: Peacock (Gooty) tarantula: arachnid · arboreal · Eastern Ghats (AP) only · Critically Endangered.

UPSC 2024. Consider the following pairs: Country — Animal found in its natural habitat

1. Brazil — Indri — WRONG — Madagascar
2. Indonesia — Elk — WRONG — the cold north
3. Madagascar — Bonobo — WRONG — DR Congo only

Answer: (d) None

Remember: Lemurs (indri) = Madagascar only · Bonobo = DR Congo only · Elk = cold northern forests.

UPSC 2023. Which one of the following makes a tool with a stick to scrap insects from a hole in a tree or a log of wood?

Answer: (b) Orangutan

Remember: Stick tool for insects = orangutan (and chimp). Sloth bear = lips and suction, no tool.

UPSC 2026. With respect to the Western Hoolock Gibbons, which of the following statements is/are correct?

1. A Sanctuary in North-east India is home to this ape species listed as Endangered in the IUCN Red List. — CORRECT — Hollongapar, Assam
2. They have specialized brachiation and can easily swing between trees. — CORRECT — arm-swinging
3. They possess a strong and heavy build like gorillas, yet are remarkably agile tree climbers. — WRONG — light and slender

Answer: (b) 1 and 2

Remember: Western hoolock = India’s only ape · Endangered · Hollongapar (Assam) · light body + brachiation.

UPSC 2026. With reference to Madhav National Park, which of the following statements is/are correct?

1. It was declared a Tiger Reserve in India in 2025. — CORRECT — India’s 58th tiger reserve
2. Sakhya Sagar, which is designated as a Ramsar Site, is situated within this National Park. — CORRECT — Ramsar site since 2022
3. Its area is shared between Madhya Pradesh and Rajasthan. — WRONG — only Madhya Pradesh

Answer: (b) 1 and 2

Remember: Madhav = Shivpuri (MP) · 58th Tiger Reserve (March 2025) · Sakhya Sagar Ramsar lake inside.

UPSC 2020. Among the following Tiger Reserves, which one has the largest area under “Critical Tiger Habitat”?

Answer: (c) Nagarjunsagar-Srisailam

Remember: Largest tiger reserve = Nagarjunsagar-Srisailam (Nallamala). Oldest = Corbett. Core = CTH, notified under the Wildlife Act.

UPSC 2020. Which of the following Protected Areas are located in the Cauvery basin?

1. Nagarhole National Park — YES — Cauvery basin
2. Papikonda National Park — NO — Godavari basin
3. Sathyamangalam Tiger Reserve — YES — Cauvery basin
4. Wayanad Wildlife Sanctuary — YES — Cauvery basin

Answer: (c) 1, 3 and 4 only

Remember: Nilgiri tri-junction (Nagarhole · Bandipur · Wayanad · Mudumalai · Sathyamangalam) = Cauvery country. Papikonda = Godavari.

UPSC 2014. With reference to ‘Eco-Sensitive Zones’, which of the following statements is/are correct?

1. Eco-Sensitive Zones are the areas that are declared under the Wildlife (Protection) Act, 1972. — WRONG — wrong Act
2. The purpose of the declaration of Eco-Sensitive Zones is to prohibit all kinds of human activities in those zones except agriculture. — WRONG — it regulates, it does not ban everything

Answer: (d) Neither 1 nor 2

Remember: Park or sanctuary = Wildlife Act 1972. The buffer around it (ESZ) = Environment Protection Act 1986. ESZ regulates, it does not freeze.

UPSC 2012. In which one among the following categories of protected areas in India are local people not allowed to collect and use the biomass?

Answer: (b) National Parks

Remember: Strictness ladder: National Park > Sanctuary > Ramsar site > Biosphere Reserve.

UPSC 2012. Vultures which used to be very common in Indian countryside some years ago are rarely seen nowadays. This is attributed to

Answer: (b) a drug used by cattle owners for treating their diseased cattle

Remember: Vulture crash = veterinary diclofenac → kidney failure. Banned 2006; safe substitute = meloxicam.

UPSC 2016. ‘Gadgil Committee Report’ and ‘Kasturirangan Committee Report’, sometimes seen in the news, are related to

Answer: (d) protection of Western Ghats

Remember: Gadgil (WGEEP, 2011) = the whole Western Ghats is sensitive. Kasturirangan (HLWG, 2013) = ~37% as ESA.

UPSC 2014. If a wetland of international importance is brought under the ‘Montreux Record’, what does it imply?

Answer: (a) Changes in ecological character have occurred, are occurring or are likely to occur in the wetland as a result of human interference.

Remember: Montreux Record = Ramsar sites under threat. India today: Keoladeo + Loktak. Chilika was removed in 2002.

UPSC 2022. Which one of the following best describes the term “greenwashing”?

Answer: (a) Conveying a false impression that a company’s products are eco-friendly and environmentally sound

Remember: Greenwashing = a false eco-friendly image. India: CCPA greenwashing guidelines, 2024.

UPSC 2025. Consider the following statements:

1. Statement I: Article 6 of the Paris Agreement on climate change is frequently discussed in global discussions on sustainable development and climate change. — CORRECT
2. Statement II: Article 6 of the Paris Agreement on climate change sets out the principles of carbon markets. — CORRECT — 6.2 and 6.4
3. Statement III: Article 6 of the Paris Agreement on climate change intends to promote inter-country non-market strategies to reach their climate targets. — CORRECT — 6.8

Answer: (a) Both Statement II and Statement III are correct and both of them explain Statement I

Remember: Article 6: 6.2 bilateral trading (ITMOs) · 6.4 UN crediting mechanism · 6.8 non-market. Rulebook completed at COP29, Baku.

UPSC 2024. Consider the following statements:

1. Statement-I: Many chewing gums found in the market are considered a source of environmental pollution. — CORRECT
2. Statement-II: Many chewing gums contain plastic as gum base. — CORRECT — and it explains Statement I

Answer: (a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

Remember: Most gum base = plastic polymers (polyvinyl acetate, polyisobutylene), which makes it non-biodegradable litter.

UPSC 2019. Why is there a great concern about the ‘microbeads’ that are released into environment?

Answer: (a) They are considered harmful to marine ecosystems.

Remember: Microbeads (<1 mm, cosmetics) → pass through treatment plants → enter marine food chains.

UPSC 1994. In recent years, there has been some concern over the threat posed by the Mathura Oil Refinery and the thermal power plants to the Taj Mahal in Agra. The scientific basis of any possible damage to the Taj is mainly

Answer: (b) acid precipitation and tropospheric ozone

Remember: Taj damage = acid rain (SO₂/NOₓ) + tropospheric ozone → marble cancer. Supreme Court: Taj Trapezium Zone (1996).

UPSC 2017. Biological Oxygen Demand (BOD) is a standard criterion for

Answer: (c) Pollution assay in aquatic ecosystems

Remember: High BOD = high organic pollution = low DO. Bathing water: BOD ≤ 3, DO ≥ 5 mg/L.

UPSC 2025. Consider the following statements:

1. Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries. — CORRECT
2. Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals. — CORRECT — explains I
3. Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content. — CORRECT — explains I

Answer: (a) Both Statement II and Statement III are correct and both of them explain Statement I

Remember: Activated carbon = adsorption on a huge surface area; made cheaply from carbon-rich waste.

UPSC 2025. The World Bank warned that India could become one of the first places where wet-bulb temperatures routinely exceed 35 °C. Which of the following statements best reflect(s) the implication of the above-said report?

1. Peninsular India will most likely suffer from flooding, tropical cyclones and droughts. — NOT the implication
2. The survival of animals including humans will be affected as shedding of their body heat through perspiration becomes difficult. — CORRECT — the direct implication

Answer: (b) II only

Remember: Wet-bulb 35 °C = the body can’t cool by sweating = the survival limit. It is heat + humidity together.

UPSC 2019. Which of the following statements are correct about the deposits of ‘methane hydrate’?

1. Global warming might trigger the release of methane gas from these deposits. — CORRECT — a feedback loop
2. Large deposits of ‘methane hydrate’ are found in Arctic Tundra and under the seafloor. — CORRECT
3. Methane in atmosphere oxidizes to carbon dioxide after a decade or two. — CORRECT — about 12 years

Answer: (d) 1, 2 and 3

Remember: Methane hydrate = methane in an ice cage · permafrost + seafloor (KG basin) · warming releases it · CH₄ → CO₂ in ~12 years.

UPSC 2026. Which of the following statements with regard to Green Hydrogen is/are correct?

1. It is decarbonized hydrogen obtained from natural gas reforming combined with carbon capture and storage (CCS). — WRONG — that is BLUE hydrogen
2. It is produced using electrolysis of water with electricity generated by renewable energy. — CORRECT — the definition
3. National Green Hydrogen Mission of India aims for abatement of nearly 50 MMT of annual greenhouse gas emissions by 2030. — CORRECT

Answer: (b) 2 and 3 only

Remember: Grey = gas, CO₂ released · Blue = gas + CCS · Green = electrolysis + renewables. NGHM: 5 MMT/yr of H₂, ~50 MMT CO₂ avoided, by 2030.

UPSC 2021. What is blue carbon?

Answer: (a) Carbon captured by oceans and coastal ecosystems

Remember: Blue carbon = ocean and coastal carbon: mangroves, salt marshes, seagrass. It is stored in the sediment.

UPSC 2022. “Biorock technology” is talked about in which one of the following situations?

Answer: (a) Restoration of damaged coral reefs

Remember: Biorock = mineral accretion by a low-voltage current → coral restoration. India: Gulf of Kachchh (ZSI).