Environmental Biology MCQs — Part 1 (Q1–Q25)

Q1. The smallest unit of ecological organization that includes both organisms and the physical environment is the:

A. Population
B. Community
C. Ecosystem ✅
D. Biome

A: A group of individuals of one species only; abiotic factors not included.
B: Multiple species together but abiotic components not explicit.
C: Ecosystem = biotic community + abiotic environment interacting as a system.
D: Biome is a regional-scale collection of ecosystems with similar climate/vegetation.

Q2. Primary productivity refers to:

A. Rate at which producers fix energy into organic matter ✅
B. Total biomass present in a system
C. Energy lost as heat in trophic transfer
D. Rate of decomposition of detritus

A: GPP/ NPP measure energy fixation by autotrophs via photosynthesis or chemosynthesis.
B: Biomass is stock, not a rate.
C: That is trophic inefficiency, not productivity.
D: Decomposition is a different process.

Q3. In most terrestrial ecosystems, the primary limiting nutrient for plant growth is:

A. Potassium
B. Nitrogen ✅
C. Calcium
D. Sodium

A/C/D: Important but typically not limiting.
B: Nitrogen often limits productivity because plants require bioavailable forms (NH₄⁺/NO₃⁻).

Q4. The 10% law of energy transfer between trophic levels implies:

A. All energy is conserved across levels
B. About one-tenth of energy is passed to the next trophic level ✅
C. Carnivores get 90% of producer energy
D. Detritivores receive no energy

A: Energy is lost as heat; not conserved in usable form.
B: Rough rule-of-thumb; actual efficiency varies (~5–20%).
C: Far too high; losses occur at each step.
D: Detritivores gain energy from dead organic matter.

Q5. The process converting atmospheric nitrogen to ammonia by microbes is:

A. Nitrification
B. Denitrification
C. Nitrogen fixation ✅
D. Ammonification

A: NH₄⁺ → NO₂⁻/NO₃⁻.
B: NO₃⁻ → N₂ gas.
C: N₂ → NH₃ by diazotrophs (e.g., Rhizobium, Azotobacter) or lightning.
D: Organic N → NH₄⁺.

Q6. Biological magnification (biomagnification) means:

A. Increase of a population’s size
B. Progressive increase in pollutant concentration up the food chain ✅
C. Dilution of toxins at higher trophic levels
D. Rapid mutation rate in polluted areas

A/D: Not the definition.
B: Lipophilic, persistent pollutants (e.g., DDT, methylmercury) magnify in predators.
C: Opposite of what is observed.

Q7. Eutrophication of lakes is primarily caused by:

A. Thermal pollution only
B. Excess nutrients (N and P) from runoff ✅
C. Heavy metal deposition alone
D. Increased wind mixing

A/C/D: May affect water but don’t directly cause algal blooms.
B: Nutrient enrichment → algal blooms → hypoxia after decomposition.

Q8. The ozone layer protects life by absorbing:

A. Infrared radiation
B. Most UV-B radiation ✅
C. Visible blue light
D. Radio waves

A/D: Not the main role.
B: Stratospheric ozone filters harmful UV-B (and some UV-C), reducing DNA damage.
C: Visible light passes largely unabsorbed.

Q9. The best indicator of organic pollution in a river (bioindicator approach) is:

A. High dissolved oxygen
B. High biochemical oxygen demand (BOD) ✅
C. High pH
D. Low turbidity

A: High DO suggests good quality.
B: Elevated BOD = more microbial respiration to degrade organics → oxygen depletion.
C/D: Can vary for many reasons; not specific.

Q10. A keystone species is one that:

A. Is the most abundant in the ecosystem
B. Has a disproportionately large effect on community structure ✅
C. Occupies the largest territory
D. Is always an apex predator

A/C: Abundance/area aren’t defining.
B: Removing keystone species causes major shifts in community composition.
D: Can be predator, pollinator, or other functional roles.

Q11. Ecological succession beginning on newly exposed rock after glaciation is:

A. Primary succession ✅
B. Secondary succession
C. Climax community
D. Retrogression

A: Starts without soil; pioneers like lichens/mosses create substrate.
B: Follows disturbance where soil remains (e.g., after fire).
C/D: Outcomes/stages, not the type.

Q12. The climax community concept refers to:

A. First stage of succession
B. Relatively stable, late-successional community under given climate ✅
C. Community with maximum species richness always
D. Community unaffected by disturbance

A: Early stage is pioneer.
B: Dynamic equilibrium; composition shaped by climate/soil.
C: Richness can vary; not always maximal.
D: All communities face disturbance.

Q13. The biological oxygen demand (BOD) test typically measures oxygen used over:

A. 1 day at 37 °C
B. 5 days at 20 °C ✅
C. 10 days at 4 °C
D. 14 days at 30 °C

A/C/D: Not standard conditions.
B: BOD₅ at 20 °C is the conventional measure.

Q14. The edge effect in fragmented habitats typically leads to:

A. More interior-specialist species
B. Increased species richness at habitat boundaries ✅
C. Lower predation near edges
D. Elimination of invasive species

A: Interior species often decline with fragmentation.
B: Edges mix species from adjacent habitats, often raising local richness (but may harm specialists).
C/D: Predation often increases; invasives may thrive at edges.

Q15. The primary greenhouse gas produced by ruminant livestock is:

A. Carbon monoxide
B. Methane (CH₄) ✅
C. Nitrous oxide
D. Ozone

A: CO is not a greenhouse gas of concern here.
B: Enteric fermentation in ruminants releases CH₄.
C: N₂O from soils/manure is also important but not the main from rumen.
D: O₃ is secondary/photochemical, not emitted by cows.

Q16. A bioindicator lichen’s absence in urban centers most often suggests:

A. High soil salinity
B. Elevated air pollution (SO₂/NOx/ozone) ✅
C. Acidic groundwater
D. High UV radiation

A/C/D: Less directly linked.
B: Many lichens are sensitive to air pollutants; their decline indicates poor air quality.

Q17. The r/K selection theory: r-selected species tend to have:

A. High fecundity, early reproduction, low parental care ✅
B. Low fecundity, delayed reproduction
C. Large body size, stable populations
D. Long generation times, density dependence

A: r-strategists exploit unpredictable environments; many small offspring.
B–D: Traits closer to K-selection.

Q18. The portion of a species’ fundamental niche that it actually occupies is the:

A. Realized niche ✅
B. Optimal niche
C. Ecotype
D. Habitat range

A: Realized niche is restricted by biotic interactions (competition, predation).
B: Not a standard niche term.
C: Genetically distinct population adapted to conditions.
D: Geographic area, not the niche concept.

Q19. Bioremediation using microbes that degrade oil is best described as:

A. Phytoremediation
B. Microbial biodegradation ✅
C. Bioaccumulation
D. Bioaugmentation with plants

A/D: Use plants; not primary for oil.
B: Hydrocarbonoclastic bacteria (e.g., Alcanivorax) degrade petroleum.
C: Uptake of contaminants, not degradation.

Q20. A wetland can improve water quality mainly by:

A. Raising salinity
B. Sediment trapping and nutrient uptake/denitrification ✅
C. Increasing flow speed
D. Eliminating evapotranspiration

A/C/D: Not true.
B: Wetlands remove sediments, assimilate P, and denitrify NO₃⁻ to N₂ gas.

Q21. Which is the best single measure of species diversity combining richness and evenness?

A. Species count only
B. Shannon–Wiener index (H′) ✅
C. Canopy cover percentage
D. Biomass per hectare

A: Ignores evenness.
B: H′ incorporates both richness and evenness.
C/D: Structural/standing stock metrics, not diversity indices.

Q22. Acid rain is mainly caused by atmospheric conversion of:

A. CO and CH₄
B. SO₂ and NOx to sulfuric and nitric acids ✅
C. O₃ and CO₂
D. NH₃ and N₂

A/C/D: Not the primary acid precursors.
B: Oxidation forms H₂SO₄ and HNO₃ → decreased pH in precipitation.

Q23. The precautionary principle in conservation suggests:

A. Act only when proof is absolute
B. Take preventive action despite scientific uncertainty to avoid harm ✅
C. Exploit resources until collapse
D. Prioritize short-term gains

A/D: Opposite of the principle.
B: Encourages early action when risks are plausible but uncertain.
C: Unsustainable.

Q24. The main reason invasive species often outcompete natives is that they:

A. Always have higher mutation rates
B. Lack natural enemies and can exploit empty niches ✅
C. Are more intelligent
D. Photosynthesize faster in all cases

A/C/D: Overgeneralizations or untrue.
B: Enemy release + preadaptation can give invaders advantage.

Q25. In population ecology, carrying capacity (K) is:

A. Number of offspring per female
B. Maximum population size the environment can sustain long-term ✅
C. Minimal viable population
D. Intrinsic growth rate

A/D: Fecundity/r, not K.
B: K is shaped by resource availability and density-dependent feedbacks.
C: MVP is a genetic/demographic threshold, not the same as K.

Environmental Biology MCQs — Part 2 (Q26–Q50)

Q26. Which biome has the highest annual primary productivity?

A. Desert
B. Tundra
C. Tropical rainforest ✅
D. Temperate grassland

A: Deserts → lowest productivity due to water limitation.
B: Tundra → very low productivity due to cold.
C: Tropical rainforests → warm, wet, year-round → highest productivity.
D: Grasslands → moderate productivity.

Q27. Which of the following gases has the highest global warming potential (GWP) per molecule?

A. Carbon dioxide
B. Methane
C. Nitrous oxide (N₂O) ✅
D. Oxygen

A: CO₂ is most abundant but lower GWP per molecule.
B: Methane is ~25x CO₂.
C: N₂O has ~300x CO₂ GWP.
D: Oxygen is not a greenhouse gas.

Q28. Which type of ecological succession occurs in abandoned agricultural fields?

A. Primary succession
B. Secondary succession ✅
C. Retrogressive succession
D. Cyclic succession

A: Primary occurs on bare rock/new land.
B: Secondary succession happens when soil is intact (e.g., old farmland).
C: Retrogression = decline in species richness.
D: Cyclic = regular shifts within a community.

Q29. The main cause of smog in urban areas is:

A. High oxygen content
B. Interaction of NOx and volatile organic compounds under sunlight ✅
C. High nitrogen fixation rates
D. Ozone depletion

A/C/D: Not causes.
B: Photochemical smog forms when NOx + VOCs react under sunlight → ground-level ozone, haze.

Q30. Which zone of a lake is most productive?

A. Profundal zone
B. Littoral zone ✅
C. Limnetic zone
D. Abyssal zone

A: Profundal → deep, dark, low productivity.
B: Littoral zone (shallow, light-penetrated, rooted plants) → highly productive.
C: Limnetic = open water, less productive than littoral.
D: Abyssal refers to ocean depths, not lakes.

Q31. Which organisms are the major producers in ocean ecosystems?

A. Seaweeds
B. Phytoplankton ✅
C. Zooplankton
D. Crustaceans

A: Seaweeds contribute but less globally.
B: Phytoplankton carry out most ocean primary production.
C/D: Consumers, not producers.

Q32. Which is a major consequence of deforestation in tropical areas?

A. Increased biodiversity
B. Loss of carbon sink and soil erosion ✅
C. Reduced albedo
D. Lower rates of desertification

A: Biodiversity declines, not increases.
B: Deforestation releases carbon, reduces soil stability.
C: Albedo often increases (bare land reflects more).
D: Deforestation often contributes to desertification.

Q33. In the carbon cycle, which process releases CO₂ into the atmosphere?

A. Photosynthesis
B. Respiration and combustion ✅
C. Carbon fixation
D. Assimilation

A: Photosynthesis consumes CO₂.
B: Respiration and combustion release CO₂.
C/D: Processes store carbon.

Q34. A species found only in a particular geographic location is called:

A. Exotic
B. Cosmopolitan
C. Endemic ✅
D. Invasive

A: Exotic = introduced.
B: Cosmopolitan = widespread.
C: Endemic = restricted to a region.
D: Invasive = non-native, spreads aggressively.

Q35. Which energy source is considered renewable?

A. Coal
B. Solar energy ✅
C. Petroleum
D. Natural gas

A/C/D: Fossil fuels are nonrenewable.
B: Solar is renewable, inexhaustible.

Q36. Which ecological pyramid can be inverted?

A. Energy pyramid
B. Pyramid of biomass (in aquatic ecosystems) ✅
C. Pyramid of numbers (always upright)
D. All pyramids

A: Energy pyramid is always upright.
B: In aquatic systems, biomass of producers (phytoplankton) is less than consumers, leading to inversion.
C: Numbers can be variable but not inverted globally.
D: Not all pyramids invert.

Q37. Which human activity contributes most to biodiversity loss?

A. Overfishing
B. Pollution
C. Climate change
D. Habitat destruction ✅

A–C: Contribute strongly.
D: Habitat loss (deforestation, land conversion) is the leading cause of biodiversity decline.

Q38. Which element is the main cause of blue baby syndrome (methemoglobinemia) in infants?

A. Phosphorus
B. Nitrate ✅
C. Sulfur
D. Lead

A/C/D: Not causes.
B: High nitrate in drinking water reduces to nitrite → interferes with hemoglobin oxygen binding.

Q39. Which biome is characterized by permafrost?

A. Desert
B. Tundra ✅
C. Temperate forest
D. Savanna

A/D: Hot, not frozen.
C: Forests lack permafrost.
B: Arctic tundra has permanently frozen subsoil (permafrost).

Q40. Which of the following pollutants is a primary contributor to acid rain?

A. Carbon dioxide
B. Sulfur dioxide ✅
C. Methane
D. Ammonia

A: CO₂ causes global warming, not acid rain.
B: SO₂ oxidizes to sulfuric acid in atmosphere.
C: CH₄ → greenhouse gas.
D: NH₃ contributes to eutrophication, not main acid rain cause.

Q41. Which renewable energy technology can harm migratory birds and bats?

A. Hydropower
B. Wind turbines ✅
C. Solar panels
D. Geothermal plants

A: Hydropower → fish migration issues.
B: Wind turbines → bird and bat collisions.
C: Solar affects land use, not birds directly.
D: Geothermal → local land issues, not birds.

Q42. Which cycle does mycorrhizal fungi primarily assist in?

A. Carbon cycle
B. Phosphorus cycle ✅
C. Nitrogen cycle
D. Sulfur cycle

A: Not directly carbon-fixing.
B: Mycorrhizae enhance plant P uptake.
C/D: Not their main role.

Q43. Which is a secondary pollutant formed in the atmosphere?

A. Sulfur dioxide
B. Carbon monoxide
C. Ozone (O₃) at ground level ✅
D. Methane

A/B/D: Primary pollutants.
C: Tropospheric ozone forms via photochemical reactions (secondary pollutant).

Q44. Which organism group acts as decomposers in ecosystems?

A. Herbivores
B. Carnivores
C. Fungi and bacteria ✅
D. Detritivores only

A/B: Consumers.
C: Fungi and bacteria decompose organic matter into nutrients.
D: Detritivores fragment matter, but microbes finalize decomposition.

Q45. Which biome has the largest terrestrial biodiversity?

A. Temperate forest
B. Tropical rainforest ✅
C. Desert
D. Tundra

A: Moderate biodiversity.
B: Rainforests → richest species diversity.
C/D: Low diversity.

Q46. Which is the main cause of coral reef bleaching?

A. Heavy fishing
B. Increased sea surface temperatures (climate change) ✅
C. High sedimentation
D. Oil spills

A/C/D: Stress corals but not main cause.
B: Elevated temperature → expulsion of symbiotic zooxanthellae → bleaching.

Q47. Which environmental treaty addresses ozone layer protection?

A. Kyoto Protocol
B. Paris Agreement
C. Montreal Protocol ✅
D. Stockholm Convention

A: Kyoto → greenhouse gases.
B: Paris → climate change.
C: Montreal Protocol controls CFCs/ozone-depleting substances.
D: Stockholm → persistent organic pollutants.

Q48. Which gas is a major component of photochemical smog?

A. Nitrous oxide
B. Ozone ✅
C. Methane
D. Hydrogen sulfide

A/C/D: Not smog drivers.
B: Ground-level ozone is main harmful component of smog.

Q49. Which natural resource is a non-renewable one?

A. Forests
B. Fossil fuels ✅
C. Groundwater
D. Fish stocks

A/C/D: Renewable if managed sustainably.
B: Fossil fuels regenerate over millions of years → nonrenewable.

Q50. The “hotspot” concept in biodiversity conservation was proposed by:

A. Darwin
B. Norman Myers ✅
C. E.O. Wilson
D. Rachel Carson

A: Theory of evolution.
B: Norman Myers (1988) introduced “biodiversity hotspots” concept.
C: Conservation biologist, but not hotspot originator.
D: Wrote Silent Spring.

Environmental Biology MCQs — Part 3 (Q51–Q75)

Q51. Which ecosystem has the highest species diversity per unit area?

A. Savanna
B. Tropical rainforest ✅
C. Desert
D. Temperate grassland

A: Savannas are rich but less than rainforests.
B: Tropical rainforests are biodiversity hotspots with maximum diversity.
C: Deserts have very low diversity.
D: Grasslands are intermediate.

Q52. Which of the following is an example of ex-situ conservation?

A. Sacred groves
B. National parks
C. Seed banks ✅
D. Biosphere reserves

A/B/D: All are in-situ conservation (on-site).
C: Ex-situ conservation preserves species outside their natural habitat.

Q53. The major source of anthropogenic carbon dioxide emissions is:

A. Deforestation only
B. Burning of fossil fuels ✅
C. Volcanoes
D. Cement in soils

A: Deforestation adds CO₂ but is secondary.
B: Combustion of coal, oil, gas is the largest source.
C: Volcanoes emit naturally, much less than humans.
D: Cement release is smaller scale.

Q54. In an energy pyramid, which level has the least available energy?

A. Producers
B. Primary consumers
C. Secondary consumers
D. Tertiary consumers ✅

A: Producers have the most stored energy.
B/C: Energy decreases with trophic transfers.
D: Tertiary consumers have the least energy due to 10% rule.

Q55. Which gas is the main contributor to the greenhouse effect naturally?

A. Carbon dioxide
B. Methane
C. Water vapor ✅
D. Nitrous oxide

A/B/D: Important but secondary.
C: Water vapor is the most abundant natural greenhouse gas.

Q56. Which organism is a detritivore?

A. Earthworm
B. Earthworm ✅
C. Tiger
D. Eagle

A/D: Carnivores, not detritivores.
B: Earthworms feed on decomposing organic matter.
C: Tiger is predator.

Q57. The “tragedy of the commons” refers to:

A. Community success in protecting resources
B. Overexploitation of shared resources due to self-interest ✅
C. Government control of forests
D. Loss of biodiversity hotspots

A: Opposite of tragedy.
B: Shared resources like fisheries, pastures are overused without regulation.
C/D: Not the definition.

Q58. Which is a greenhouse gas but not regulated under the Kyoto Protocol?

A. Carbon dioxide
B. Methane
C. Water vapor ✅
D. Nitrous oxide

A/B/D: All regulated under Kyoto.
C: Water vapor is a greenhouse gas but naturally cycled, not directly regulated.

Q59. Which trophic level do decomposers primarily act upon?

A. Producers only
B. All trophic levels ✅
C. Secondary consumers only
D. Tertiary consumers only

A: Decomposers recycle organic matter from all levels.
B: Act on dead matter from all organisms.
C/D: Too narrow.

Q60. Which ecological concept explains two species not coexisting if they compete for the same resource?

A. Keystone hypothesis
B. Competitive exclusion principle ✅
C. Neutral theory
D. Island biogeography

A: Keystone = species importance.
B: Gause’s principle: one outcompetes the other if niche overlap is complete.
C: Neutral theory = stochastic coexistence.
D: Island biogeography = species–area relationships.

Q61. Which species concept is most often used in conservation biology?

A. Morphological species concept
B. Phylogenetic species concept
C. Biological species concept ✅
D. Ecological species concept

A: Useful for fossils.
B: Genetic lineage-based.
C: Defines species by reproductive isolation; widely applied in conservation.
D: Niche-based, less common.

Q62. The major contributor to acidification of oceans is:

A. Plastic pollution
B. Dissolution of excess atmospheric CO₂ ✅
C. Oil spills
D. Thermal pollution

A/C/D: Harmful but not acidification causes.
B: CO₂ dissolves → carbonic acid → lowers pH.

Q63. Which biome is maintained by frequent fires and seasonal rainfall?

A. Desert
B. Savanna ✅
C. Tundra
D. Temperate rainforest

A/C/D: Incorrect.
B: Savannas rely on fire to prevent woody encroachment.

Q64. The largest freshwater lake by volume in the world is:

A. Lake Victoria
B. Lake Superior
C. Lake Baikal ✅
D. Lake Tanganyika

A: Largest in Africa but not by volume.
B: Largest in North America by area.
C: Lake Baikal (Russia) holds ~20% of world’s unfrozen freshwater.
D: Tanganyika is deep but smaller than Baikal.

Q65. The most common cause of desertification is:

A. Volcanic eruptions
B. Glacial retreat
C. Deforestation and overgrazing ✅
D. Earthquakes

A/B/D: Geophysical events.
C: Unsustainable land use drives desertification.

Q66. Which environmental problem is most associated with CFCs?

A. Acid rain
B. Ozone depletion ✅
C. Eutrophication
D. Desertification

A/C/D: Not caused by CFCs.
B: CFCs release chlorine radicals in stratosphere → ozone depletion.

Q67. The largest reservoir of carbon on Earth is:

A. Atmosphere
B. Oceans (dissolved carbonates) ✅
C. Plants and soils
D. Fossil fuels

A: Atmosphere holds less.
B: Oceans store the largest carbon pool as bicarbonates/carbonates.
C: Important, but smaller.
D: Fossil fuels are large but not the biggest.

Q68. Which type of biodiversity refers to variety of habitats, ecosystems, and landscapes?

A. Genetic diversity
B. Species diversity
C. Ecosystem diversity ✅
D. Functional diversity

A: Variation in genes.
B: Variety of species.
C: Diversity at ecosystem/habitat scale.
D: Variation in ecological roles.

Q69. Which is a point source pollutant?

A. Agricultural runoff
B. Discharge pipe from a factory ✅
C. Acid rain
D. Urban air pollution

A/C/D: Diffuse (non-point sources).
B: Direct, identifiable discharge = point source.

Q70. Which organism is a classic indicator of water pollution?

A. Dragonflies
B. Coliform bacteria (e.g., E. coli) ✅
C. Houseflies
D. Termites

A: Dragonflies indicate clean water.
B: Coliforms indicate fecal contamination.
C/D: Not water quality indicators.

Q71. The total dry weight of organisms per unit area at a given time is:

A. Productivity
B. Biomass ✅
C. Trophic efficiency
D. Ecological niche

A: Rate of energy fixation.
B: Biomass is standing crop of organic matter.
C: Energy transfer efficiency.
D: Role of a species.

Q72. Which region has the world’s largest tropical rainforest?

A. Africa
B. Amazon Basin (South America) ✅
C. Southeast Asia
D. Australia

A: Congo basin is second-largest.
B: Amazon is the largest tropical rainforest on Earth.
C: Significant but smaller.
D: Limited tropical rainforest.

Q73. The Red Data Book lists:

A. Soil types
B. Threatened and endangered species ✅
C. Renewable resources
D. Natural reserves

A/C/D: Not the focus.
B: Maintained by IUCN to document species at risk.

Q74. Which cycle involves both atmospheric and sedimentary phases?

A. Carbon cycle
B. Sulfur cycle ✅
C. Nitrogen cycle
D. Water cycle

A: Mostly atmospheric/biotic.
B: Sulfur cycle includes atmospheric SO₂ and sedimentary sulfates.
C: Primarily atmospheric/biotic.
D: Water cycle = hydrologic only.

Q75. Which practice is most sustainable for soil fertility?

A. Monocropping
B. Overuse of chemical fertilizers
C. Crop rotation and organic manure ✅
D. Slash-and-burn

A/B/D: Lead to degradation.
C: Rotation + organic manure maintain soil nutrients and structure.

Environmental Biology MCQs — Part 4 (Q76–Q100)

Q76. Which international agreement specifically addresses climate change?

A. Montreal Protocol
B. Kyoto Protocol ✅
C. Basel Convention
D. Stockholm Convention

A: Montreal → ozone depletion.
B: Kyoto targets reduction of greenhouse gas emissions.
C: Basel regulates hazardous waste trade.
D: Stockholm bans persistent organic pollutants.

Q77. Which is a non-point source of water pollution?

A. Factory discharge pipe
B. Sewage treatment outlet
C. Agricultural runoff ✅
D. Oil spill from tanker

A/B/D: All point sources.
C: Agricultural runoff is diffuse, not from a single discharge.

Q78. Which organism is often used as a bioindicator of heavy metal pollution?

A. Earthworm
B. Mussels ✅
C. Frogs
D. Fish

A: Good for soil contamination.
B: Mussels accumulate heavy metals → used in biomonitoring.
C: Amphibians are indicators for pesticides.
D: Fish are used for broader pollution, not metals specifically.

Q79. The green revolution mainly relied on:

A. GM crops only
B. High-yielding crop varieties, fertilizers, and irrigation ✅
C. Natural fertilizers alone
D. Deforestation for farmland

A: GM crops came later.
B: High-yield varieties + fertilizers + pesticides + irrigation improved yields.
C: Natural fertilizers were insufficient alone.
D: Deforestation wasn’t part of the Green Revolution.

Q80. Which process converts nitrates back to atmospheric nitrogen?

A. Nitrogen fixation
B. Nitrification
C. Denitrification ✅
D. Ammonification

A: N₂ → NH₃.
B: NH₄⁺ → NO₂⁻/NO₃⁻.
C: Denitrifying bacteria (e.g., Pseudomonas) reduce NO₃⁻ to N₂ gas.
D: Organic N → NH₄⁺.

Q81. Which country generates the highest percentage of electricity from renewable sources?

A. USA
B. China
C. Iceland ✅
D. India

A/B/D: Use significant fossil fuels.
C: Iceland uses nearly 100% renewable (hydropower + geothermal).

Q82. Which natural disaster most contributes to soil erosion?

A. Earthquake
B. Volcanic eruption
C. Flooding ✅
D. Tsunami

A/B/D: Cause destruction but not major soil erosion.
C: Floods remove topsoil → erosion and fertility loss.

Q83. Which environmental law in India deals specifically with wildlife protection?

A. Air Act 1981
B. Wildlife Protection Act 1972 ✅
C. Forest Conservation Act 1980
D. Water Act 1974

A/D: Pollution control acts.
C: Focused on forest use.
B: Protects wild animals, plants, and habitats.

Q84. Which cycle lacks a significant atmospheric component?

A. Phosphorus cycle ✅
B. Nitrogen cycle
C. Carbon cycle
D. Water cycle

A: Phosphorus cycle is sedimentary, lacking a major gaseous phase.
B–D: All include atmosphere.

Q85. Which is an example of in-situ conservation?

A. Seed bank
B. Zoo
C. National park ✅
D. Botanical garden

A/B/D: Ex-situ methods.
C: National parks conserve species in their natural habitats.

Q86. Which is the leading cause of global amphibian decline?

A. Overhunting
B. Habitat loss, climate change, and chytrid fungus disease ✅
C. Deforestation only
D. Natural predation

A/D: Not major reasons globally.
B: Combined threats, especially chytrid fungal infections, drive declines.

Q87. Which practice contributes to sustainable fisheries?

A. Overfishing
B. Catch limits and marine protected areas ✅
C. Trawling everywhere
D. Introducing exotic species

A/C/D: Harmful to fisheries.
B: Quotas + protected areas ensure long-term sustainability.

Q88. Which organism is the primary producer in hydrothermal vent ecosystems?

A. Zooplankton
B. Chemosynthetic bacteria ✅
C. Fish
D. Tube worms

A/C/D: Consumers.
B: Bacteria oxidize H₂S to fix carbon → primary producers.

Q89. Which region is known as the “lungs of the Earth”?

A. Congo Basin
B. Amazon Rainforest ✅
C. Taiga
D. Great Barrier Reef

A: Congo also large but smaller.
B: Amazon produces ~20% of Earth’s oxygen → called Earth’s lungs.
C/D: Important ecosystems but not termed “lungs.”

Q90. Which is the main cause of ozone depletion?

A. Methane
B. Chlorofluorocarbons (CFCs) ✅
C. Nitrous oxide
D. Carbon monoxide

A/D: Not ozone-depleting.
B: CFCs release chlorine radicals that destroy ozone.
C: N₂O contributes but less than CFCs.

Q91. Which environmental factor determines the taiga biome?

A. Hot climate
B. Cold climate with coniferous forests ✅
C. Rainfall > 200 cm
D. Permafrost all year

A: Wrong.
B: Taiga = boreal forest → cold winters, conifer trees.
C: Rainfall is moderate.
D: Permafrost = tundra.

Q92. Which type of solid waste is biodegradable?

A. Plastic bags
B. Food scraps and paper ✅
C. Aluminum cans
D. Glass bottles

A/C/D: Non-biodegradable.
B: Organic matter and paper decompose naturally.

Q93. Which international event first recognized sustainable development formally?

A. Montreal Protocol 1987
B. Rio Earth Summit 1992 ✅
C. Kyoto Protocol 1997
D. Stockholm Conference 1972

A: Ozone treaty.
B: Rio Summit introduced Agenda 21 and sustainable development concept.
C: Climate treaty.
D: Stockholm focused on environment, not SD concept.

Q94. Which of the following contributes to urban heat island effect?

A. Tall trees in cities
B. Concrete, asphalt, reduced vegetation ✅
C. High wind speed
D. Abundant water bodies

A/D: Reduce heat.
B: Heat absorption + less evapotranspiration raise urban temps.
C: Wind disperses heat.

Q95. Which environmental movement in India aimed at preventing deforestation?

A. Narmada Bachao Andolan
B. Silent Valley Movement
C. Chipko Movement ✅
D. Bishnoi Movement

A: Focused on dam displacement.
B: Prevented dam in Kerala forest.
C: Villagers hugged trees to prevent logging (1970s, Uttarakhand).
D: Bishnoi community conserved wildlife historically.

Q96. Which ecosystem service is considered provisioning?

A. Climate regulation
B. Food and fresh water supply ✅
C. Pollination
D. Soil formation

A/C/D: Regulating/supporting services.
B: Provisioning services = tangible products like food, water, timber.

Q97. Which gas is released from landfills and contributes to climate change?

A. Oxygen
B. Nitrogen
C. Methane ✅
D. Ozone

A/B/D: Not landfill gases.
C: Anaerobic decomposition in landfills → methane.

Q98. Which biome is dominated by drought-resistant shrubs and mild, wet winters?

A. Desert
B. Chaparral (Mediterranean scrubland) ✅
C. Grassland
D. Savanna

A: Too dry.
B: Chaparral = shrubland biome with Mediterranean climate.
C/D: Grass-dominated, different climate.

Q99. Which layer of the atmosphere contains the ozone layer?

A. Troposphere
B. Stratosphere ✅
C. Mesosphere
D. Thermosphere

A: Closest to Earth’s surface.
B: Ozone layer lies in stratosphere (~15–35 km altitude).
C/D: Higher layers, no ozone.

Q100. The main purpose of an environmental impact assessment (EIA) is:

A. Increase industrial output
B. Evaluate environmental effects before approving projects ✅
C. Reduce fossil fuel imports
D. Plant more trees

A/C/D: Not the purpose.
B: EIA predicts and mitigates environmental damage before project approval.

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