UPSC Prelims 2024
Environment & Ecology Previous Year Questions (PYQs)

Detailed Explanation:

Correct Answer: ✅ Option 1 (Statement 2 only)

The World Toilet Organization (WTO) is an international non-profit organization dedicated to improving sanitation and ending the global sanitation crisis through advocacy, awareness, and capacity building.

❌ Statement 1 is Incorrect: The World Toilet Organization is not a United Nations agency. It is an independent international non-profit organization founded in 2001 in Singapore.

✅ Statement 2 is Correct: The organization launched initiatives such as World Toilet Summit, World Toilet College, and played a key role in promoting World Toilet Day to raise awareness about sanitation issues worldwide.

❌ Statement 3 is Incorrect: Its primary role is advocacy, education, networking, and capacity building, not providing grants to countries. Funding sanitation projects is mainly undertaken by governments, development banks, and international agencies.

Short Notes: World Toilet Organization (WTO)

• Established in 2001 in Singapore.

• It is an international non-profit organization, not a UN agency.

• Works to improve global sanitation and hygiene.

• Organizes the World Toilet Summit to discuss sanitation challenges.

• Founded the World Toilet College for sanitation training and capacity building.

• Instrumental in advocating for World Toilet Day (19 November).

• Focuses on awareness, advocacy, partnerships, and knowledge sharing.

• Supports the achievement of SDG 6 (Clean Water and Sanitation).

Detailed Explanation:

Correct Answer: ✅ Option 1

The 100 Million Farmers (100MF) initiative is a global platform launched by the World Economic Forum to accelerate the transition towards net-zero, nature-positive, and resilient food and water systems. It aims to support farmers in adopting sustainable agricultural practices while improving livelihoods and climate resilience.

✅ Statement I is Correct: The initiative focuses on creating net-zero (carbon), nature-positive, and water-resilient agricultural systems.

✅ Statement II is Correct: It aims to enhance farmer resilience, improve productivity, and promote regenerative agriculture practices.

❌ Option B is Incorrect: This describes organizations promoting organic animal husbandry, not the 100 Million Farmers initiative.

❌ Option C is Incorrect: This refers to a blockchain-based fertilizer trading platform, unrelated to 100 Million Farmers.

❌ Option D is Incorrect: While FPOs improve market access, the primary goal of 100 Million Farmers is sustainable agricultural transformation, not merely forming producer organizations.

Short Notes: 100 Million Farmers Initiative

• Launched by the World Economic Forum (WEF).

• Target: Support 100 million farmers by 2030.

• Promotes regenerative and climate-smart agriculture.

• Focuses on net-zero, nature-positive food systems.

• Enhances soil health, biodiversity, and water efficiency.

• Seeks to improve farmer incomes and resilience.

• Encourages public-private partnerships in agriculture.

• Contributes to global climate and sustainability goals.

Detailed Explanation:

Answer: Option 1 — Only one

Among the three trees mentioned, only Red Sanders is native to India, specifically endemic to the Eastern Ghats of Andhra Pradesh. Both Cashew and Papaya are exotic species that were introduced to India from the Americas by European traders during the colonial period.

✅ Red Sanders – Native to India: Endemic to the Eastern Ghats, particularly Andhra Pradesh, known for its valuable reddish wood.
❌ Cashew – Not native: Originally from Brazil, introduced to India by Portuguese traders in the 16th century.
❌ Papaya – Not native: Originated in southern Mexico and Central America, brought to India during colonial times.

📝 Short Notes: Native vs. Exotic Trees of India

• Red Sanders (Pterocarpus santalinus): Endemic to India, found exclusively in the Eastern Ghats of Andhra Pradesh and parts of Karnataka. It is listed in CITES Appendix II due to illegal logging and trade. The tree produces valuable red heartwood used in furniture, musical instruments, and traditional medicine.
• Cashew (Anacardium occidentale): Native to Brazil, introduced to Goa by Portuguese colonizers in the 16th century. India is now the world's largest producer and exporter of cashew nuts, with major cultivation in Kerala, Karnataka, Goa, and Maharashtra.
• Papaya (Carica papaya): Originated in tropical Americas (southern Mexico and Central America). Brought to India by Portuguese and Spanish traders. India is now one of the largest producers of papaya globally, cultivated throughout tropical and subtropical regions.
• Other Native Indian Trees: Neem (Azadirachta indica), Banyan (Ficus benghalensis), Peepal (Ficus religiosa), Sal (Shorea robusta), Teak (Tectona grandis), and Sandalwood (Santalum album).
• Other Exotic Trees in India: Eucalyptus (Australia), Pine (temperate regions), Rubber (Brazil), Coffee (Ethiopia), and Tea (China).
• Conservation Concern: Red Sanders is classified as 'Endangered' on the IUCN Red List due to overexploitation for its valuable timber, leading to strict protection measures and anti-smuggling operations.

Detailed Explanation:

Answer: Option 4 — None

None of the given country-animal pairs are correctly matched. Each animal mentioned is native to a completely different geographical region than the country paired with it.

❌ Pair 1 – Incorrect: Indri is a lemur species endemic only to Madagascar, not Brazil.
❌ Pair 2 – Incorrect: Elk (Cervus canadensis) are found in North America and parts of Asia, not in Indonesia.
❌ Pair 3 – Incorrect: Bonobo (Pan paniscus) is a great ape found exclusively in the Democratic Republic of Congo, not Madagascar.

📝 Short Notes: Endemic Species and Their Natural Habitats

• Endemic species: Species found exclusively in one geographic location and nowhere else naturally in the world
• Madagascar biodiversity: Island isolation for ~88 million years has led to extraordinary endemic biodiversity, especially lemurs, chameleons, and unique flora
• Conservation importance: Understanding natural habitats is crucial for wildlife conservation and preventing extinction of endemic species

Detailed Explanation:

Answer: Option 4 — Power plants using fossil fuels

Power plants burning fossil fuels, particularly coal, are the largest source of sulfur dioxide (SO₂) emissions globally according to the EPA. Coal contains high levels of sulfur, and when combusted for electricity generation, it releases substantial amounts of SO₂ into the atmosphere. While ships using bunker fuel, metal extraction processes, and locomotives also contribute to SO₂ emissions, their combined contribution is significantly lower than emissions from fossil fuel-based power generation.

📝 Short Notes: Sulfur Dioxide (SO₂) Emissions

• Primary Source: Coal-fired power plants are responsible for approximately 65-70% of global SO₂ emissions, as coal contains 0.5-3% sulfur by weight.
• Ships: Maritime vessels using heavy bunker fuel (high sulfur content) are the second major source, especially in coastal and port areas; regulations like MARPOL Annex VI now limit sulfur content in marine fuels.
• Metal Smelting: Extraction of metals like copper, zinc, and lead from sulfide ores releases SO₂ during roasting and smelting processes, contributing 5-10% of total emissions.
• Locomotives: Diesel-powered trains contribute minimally to SO₂ emissions due to lower sulfur content in diesel fuel and relatively smaller fuel consumption compared to power plants.
• Environmental Impact: SO₂ causes acid rain, respiratory problems, and contributes to particulate matter (PM2.5) formation; it also damages vegetation and corrodes buildings.
• Control Measures: Flue gas desulfurization (FGD/scrubbers), switching to low-sulfur fuels, and renewable energy transition are key mitigation strategies.

Detailed Explanation:

Answer: Option 1 — Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

Chewing gums are a significant source of environmental pollution, and Statement-II directly explains why this is the case.

✅ Statement-I – Correct: Many chewing gums found in the market are considered a source of environmental pollution due to their non-biodegradable nature and improper disposal, leading to persistent litter in public spaces.

✅ Statement-II – Correct: Many chewing gums contain plastic polymers (such as polyisobutylene, polyvinyl acetate, or polyethylene) as their gum base, which makes them non-biodegradable and environmentally persistent.

Explanation: Statement-II explains Statement-I because the presence of plastic-based gum base is the primary reason why chewing gums become environmental pollutants. These synthetic polymers do not decompose naturally and remain in the environment for years, creating cleanup challenges and contributing to plastic pollution.

📝 Short Notes: Chewing Gum and Environmental Pollution

• Gum Base Composition: Modern chewing gums typically use synthetic polymers (plastics) like polyisobutylene and polyvinyl acetate instead of natural chicle latex.
• Non-Biodegradable Nature: These plastic-based gum bases can take years to decades to break down in the environment, persisting as microplastic pollution.
• Urban Pollution: Discarded chewing gum is one of the most common forms of street litter, requiring expensive removal processes (often using chemical solvents or freezing techniques).
• Environmental Impact: Improperly disposed gum contributes to plastic pollution, can harm wildlife if ingested, and creates unsightly stains on pavements and public infrastructure.
• Biodegradable Alternatives: Some companies are now developing plant-based, biodegradable gum alternatives to address environmental concerns.

Detailed Explanation:

Answer: Option 3 — Insects

All three organisms—Cicada, Froghopper, and Pond Skater—are classified as insects belonging to different families within the class Insecta. Cicadas are known for their loud mating calls, froghoppers (spittlebugs) are famous for the foam they produce as nymphs, and pond skaters use surface tension to walk on water.

📝 Short Notes: Classification of Common Insects

• Cicada: Order Hemiptera; known for their distinctive loud buzzing sounds produced by males during mating season; have a long lifecycle with some species emerging every 13-17 years.
• Froghopper (Spittlebug): Order Hemiptera; small jumping insects; nymphs produce foam (cuckoo spit) on plants for protection; adults are powerful jumpers.
• Pond Skater (Water Strider): Order Hemiptera, family Gerridae; use surface tension and hydrophobic legs to walk on water; predators of small aquatic organisms.
• Common Feature: All three belong to Order Hemiptera (true bugs), characterized by piercing-sucking mouthparts and incomplete metamorphosis.
• Ecological Role: These insects play important roles as herbivores, predators, and prey in their respective ecosystems.

Detailed Explanation:

Answer: Option 2 — Congo Basin

The Congo Basin contains the world's largest tropical peatland complex, known as the Cuvette Centrale, which spans approximately 145,000 square kilometres across the Republic of Congo and the Democratic Republic of Congo. This peatland stores about 30 billion tonnes of carbon—equivalent to roughly three years of global fossil fuel emissions—making its preservation critical for climate stability. The destruction of this peatland through drainage or land-use changes would release massive amounts of carbon dioxide, significantly accelerating global climate change.

📝 Short Notes: Major Tropical Peatlands

• Peatlands are wetland ecosystems where waterlogged conditions prevent organic matter from fully decomposing, leading to carbon accumulation over thousands of years
• Tropical peatlands store carbon both in vegetation and in deep peat soils (can be several meters deep)
• Drainage and conversion of peatlands for agriculture releases stored carbon as CO₂ and N₂O
• Protection of peatlands is crucial for climate change mitigation strategies

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three statements about PFAS (perfluoroalkyl and polyfluoroalkyl substances) are correct. These synthetic chemicals, often called 'forever chemicals', are widely used in consumer products and are characterized by their environmental persistence and bioaccumulation potential.

✅ Statement 1 – Correct: PFAS are widely detected in drinking water, food items, and food packaging materials due to their extensive use in consumer products and their ability to leach into the environment.
✅ Statement 2 – Correct: PFAS are called 'forever chemicals' because the strong carbon-fluorine bond makes them extremely resistant to environmental degradation processes.
✅ Statement 3 – Correct: Due to their persistence, PFAS accumulate in the tissues of animals and humans over time, leading to bioaccumulation and potential health risks.

📝 Short Notes: PFAS (Forever Chemicals)

• Full Form: Perfluoroalkyl and Polyfluoroalkyl Substances
• Nickname: 'Forever Chemicals' due to their extremely persistent nature
• Chemical Structure: Contain strong carbon-fluorine bonds that resist breakdown
• Common Uses: Non-stick cookware, water-repellent fabrics, firefighting foams, food packaging, cosmetics
• Environmental Persistence: Do not degrade naturally; accumulate in soil, water, and air
• Health Concerns: Bioaccumulation leads to potential cancer risk, liver damage, immune system effects, and developmental issues
• Global Concern: Found in blood samples of humans and wildlife worldwide; subject to increasing regulatory scrutiny

Detailed Explanation:

Answer: Option 1 — Fig

Fig trees share a unique obligate mutualistic relationship with fig wasps, which are the only insects capable of pollinating fig flowers. The fig wasp enters the enclosed syconium (fig fruit structure) through a tiny opening called the ostiole to lay eggs, simultaneously pollinating the internal flowers. This highly specialized relationship is a classic example of coevolution, where both species have evolved together over millions of years, making them entirely dependent on each other for survival and reproduction.

Why other options are incorrect:
❌ Option 2 – Mahua: Mahua (Madhuca indica) is pollinated by various insects including bees, moths, and even bats, not a single specialized pollinator.
❌ Option 3 – Sandalwood: Sandalwood is primarily pollinated by bees and flies; it is a hemiparasitic plant that relies on host trees for nutrients but has no unique insect pollinator.
❌ Option 4 – Silk Cotton: Silk cotton trees are pollinated by bats and birds, not by a specialized insect species.

📝 Short Notes: Fig-Wasp Mutualism

• Obligate Mutualism: Both fig and fig wasp are entirely dependent on each other—figs cannot reproduce without fig wasps, and fig wasps cannot reproduce without figs.
• Syconium Structure: The fig is not a true fruit but a syconium—a hollow, fleshy structure with flowers enclosed inside.
• Pollination Process: Female fig wasps enter through the ostiole (small opening), lay eggs inside ovaries, and pollinate flowers in the process. Male wasps are wingless and mate inside the fig.
• Coevolution: This relationship has evolved over approximately 80 million years, with over 750 species of figs, each typically having its own specialized wasp species.
• Ecological Importance: Figs are keystone species in tropical ecosystems, providing food for numerous animals during lean periods when other fruits are scarce.

Detailed Explanation:

Answer: Option 3 — All three

All three groups mentioned in the question—butterflies, fish, and frogs—have poisonous species among them. Butterflies like the Monarch sequester toxins from their larval diet of milkweed, making them poisonous to predators. Many fish species such as pufferfish, lionfish, and stonefish possess deadly venom or toxins. Poison dart frogs are classic examples of amphibians that secrete potent toxins through their skin as a defense mechanism.

📝 Short Notes: Poisonous Species in Different Animal Groups

• Poisonous Butterflies: Monarch butterflies accumulate cardiac glycosides from milkweed plants during their caterpillar stage, making them toxic to birds and other predators. Other examples include the Pipevine Swallowtail.
• Poisonous Fish: Pufferfish contain tetrodotoxin, a neurotoxin deadly to humans. Lionfish and stonefish have venomous spines. Stingrays possess venomous barbs on their tails.
• Poisonous Frogs: Poison dart frogs (family Dendrobatidae) of Central and South America secrete alkaloid toxins through their skin. The Golden Poison Frog is one of the most toxic vertebrates on Earth.
• Mechanism of Toxicity: Some species produce toxins endogenously (within their bodies), while others sequester them from their diet (like Monarch butterflies and poison dart frogs).
• Purpose of Poison: These toxins serve primarily as defense mechanisms against predators, advertised through warning coloration (aposematism) in many cases.

Detailed Explanation:

Answer: Option 3 — 1, 2, 3 and 4

All four materials listed can serve as feedstock for producing Sustainable Aviation Fuel (SAF). Agricultural residues and wood mill waste are lignocellulosic biomass sources that can be converted through thermochemical or biochemical processes. Corn grain provides fermentable sugars for ethanol production, which can be upgraded to SAF. Wastewater treatment sludge, rich in organic matter, can undergo anaerobic digestion to produce biogas, subsequently convertible to SAF.

✅ Statement 1 – Correct: Agricultural residues (crop stalks, husks, leaves) are viable lignocellulosic biomass sources for SAF production through various conversion pathways.
✅ Statement 2 – Correct: Corn grain contains fermentable sugars that can be converted to ethanol and further processed into SAF via alcohol-to-jet fuel pathways.
✅ Statement 3 – Correct: Wastewater treatment sludge is rich in organic matter and can be converted to biogas through anaerobic digestion, which can then be upgraded to SAF.
✅ Statement 4 – Correct: Wood mill waste (sawdust, wood chips, bark) is a lignocellulosic material convertible to SAF through gasification, pyrolysis, or other thermochemical processes.

📝 Short Notes: Sustainable Aviation Fuel (SAF)

• Definition: SAF is a drop-in replacement for conventional jet fuel, produced from sustainable feedstocks, reducing lifecycle carbon emissions by up to 80%.
• Feedstock Categories: Includes agricultural residues, forestry waste, municipal solid waste, industrial waste, algae, and dedicated energy crops.
• Production Pathways: Major technologies include Fischer-Tropsch synthesis, Hydroprocessed Esters and Fatty Acids (HEFA), Alcohol-to-Jet (ATJ), and gasification.
• Certification: SAF must meet ASTM D7566 standards and can be blended with conventional jet fuel up to 50% (some pathways allow 100%).
• Global Initiatives: ICAO's CORSIA scheme, EU's ReFuelEU Aviation, and US SAF Grand Challenge aim to scale SAF production and adoption.
• Indian Context: India is exploring SAF production from agricultural waste, used cooking oil, and other biomass sources to decarbonize aviation sector.

Detailed Explanation:

Answer: Option 3 — Statement-I is correct, Statement-II is incorrect

This question tests knowledge about the Indian Flying Fox and the Wild Life (Protection) Act, 1972. While the current model answer states both statements are incorrect, the correct answer as per the original marking was Option 3, indicating Statement-I was considered correct at the time of the exam.

✅ Statement-I – Correct (as per original context): Historically, the Indian Flying Fox was placed under Schedule V (vermin category) in the Wild Life (Protection) Act, 1972, before the 2022 amendments abolished this schedule.

❌ Statement-II – Incorrect: The Indian Flying Fox (Pteropus medius) is a large frugivorous bat that feeds on fruits, nectar, and flowers, not on blood. Blood-feeding behavior is characteristic of vampire bats found in Latin America, not fruit bats.

📝 Short Notes: Indian Flying Fox and Wildlife Protection

Detailed Explanation:

Answer: Option 2 — Only three

Parasitoid species are organisms that live on or in a host organism, eventually killing it. Among the listed organisms, parasitoid species are found in Carabid beetles (some species are parasitoids of other insects), Flies (Tachinid flies and other Diptera families include numerous parasitoids), and Wasps (Hymenoptera has extensive parasitoid families). Centipedes are predators that directly hunt and kill prey, while termites are herbivorous social insects feeding on plant matter, neither being parasitoids.

📝 Short Notes: Parasitoids

• Definition: Parasitoids are organisms that spend a significant portion of their life attached to or within a single host organism, which they ultimately kill. They differ from true parasites (which usually don't kill the host) and predators (which kill multiple prey).
• Carabid Beetles: While most are predatory, some species (particularly in genera like Brachinus and Lebia) exhibit parasitoid behavior, especially targeting pupae of other insects.
• Flies (Diptera): Tachinidae family is the largest group of parasitoid flies, with over 10,000 species. Other families like Bombyliidae and Sarcophagidae also include parasitoid species.
• Wasps (Hymenoptera): The most diverse parasitoid group, including families like Ichneumonidae, Braconidae, Chalcidoidea, and many others. They parasitize various life stages of insects and other arthropods.
• Centipedes: Chilopoda are venomous predators that actively hunt arthropods and small invertebrates; they do not exhibit parasitoid behavior.
• Termites: Isoptera are eusocial insects primarily feeding on cellulose from wood and plant material; they are decomposers, not parasitoids.

Detailed Explanation:

Answer: Option 1 — 1 and 2 only

This question tests knowledge about the behavioral characteristics of big cats, particularly lions, cheetahs, and leopards. Understanding territorial marking, breeding patterns, and vocal capabilities of these species is important for wildlife ecology.

✅ Statement 1 – Correct: Lions do not have a strictly defined breeding season and can breed throughout the year, though some seasonal peaks may occur depending on environmental conditions like prey availability and rainfall.

✅ Statement 2 – Correct: Cheetahs lack the specialized larynx structure (hyoid bone apparatus) that allows other big cats to roar; instead, they produce chirps, purrs, and high-pitched calls similar to birds.

❌ Statement 3 – Incorrect: Male leopards, like male lions, actively use scent marking (urine spraying, scraping, and fecal deposits) to proclaim and defend their territories; this statement incorrectly suggests leopards do not engage in territorial scent marking.

📝 Short Notes: Big Cats - Behavioral Characteristics

• Roaring mechanism: Lions, tigers, leopards, and jaguars belong to genus Panthera with a flexible hyoid bone that enables roaring.
• Cheetah distinction: Belongs to genus Acinonyx; has a fixed hyoid bone, preventing roaring but allowing continuous purring.
• Territorial behavior: All big cats use scent marking (urine, feces, gland secretions) and visual cues (scratch marks) to establish territories.
• Breeding patterns: Most big cats can breed year-round, but environmental factors (prey density, climate) influence peak breeding times.

Detailed Explanation:

Answer: Option 4 — Wastewater treatment technologies

Membrane Bioreactors (MBRs) are advanced wastewater treatment systems that combine conventional biological treatment processes with membrane filtration (microfiltration or ultrafiltration). They are highly efficient in removing contaminants, producing high-quality effluent, and require less space compared to traditional treatment methods. MBRs are widely used in municipal and industrial wastewater treatment applications due to their superior performance in removing suspended solids, pathogens, and organic pollutants.

📝 Short Notes: Membrane Bioreactors (MBRs)

• Technology: Combines biological degradation with membrane filtration in a single unit
• Membrane Types: Uses microfiltration (MF) or ultrafiltration (UF) membranes with pore sizes of 0.1-0.4 microns
• Advantages: High effluent quality, smaller footprint, complete retention of biomass, and better pathogen removal
• Applications: Municipal wastewater treatment, industrial effluent treatment, water reuse and recycling
• Limitations: Higher capital and operational costs, membrane fouling issues, energy-intensive operation
• Environmental Significance: Enables water reuse, reduces pollution load, and supports circular economy in water management