🌸Chapter 12
Ecosystem
(MCQs)
1–10: Basics of Ecosystem
Q1.
Who coined the term “ecosystem”?
A. Haeckel
B. Odum
C. A.G. Tansley
D. Elton
Answer:
C. A.G. Tansley
Explanation: A.G. Tansley (1935) introduced the term “ecosystem” to
denote the functional unit of nature.
Q2.
Which of the following is a biotic component of an ecosystem?
A. Soil
B. Water
C. Plants
D. Temperature
Answer:
C. Plants
Explanation: Biotic components are living organisms like plants,
animals, and microbes.
Q3.
Abiotic factors include:
A. Fungi
B. Soil
C. Herbivores
D. Birds
Answer:
B. Soil
Explanation: Abiotic components are non-living elements like soil,
water, air, temperature.
Q4.
Ecosystem can be:
A. Natural
B. Artificial
C. Both A and B
D. None
Answer:
C. Both A and B
Explanation: Natural (forests, ponds) and artificial (gardens,
aquariums) ecosystems exist.
Q5.
Which of the following is a producer?
A. Lion
B. Grass
C. Snake
D. Frog
Answer:
B. Grass
Explanation: Producers (autotrophs) synthesize their own food via
photosynthesis.
Q6.
Consumers are:
A. Autotrophs
B. Heterotrophs
C. Decomposers
D. All of the above
Answer:
B. Heterotrophs
Explanation: Consumers depend on other organisms for energy.
Q7.
Decomposers are important because they:
A. Produce food
B. Eat herbivores
C. Recycle nutrients
D. Consume carnivores
Answer:
C. Recycle nutrients
Explanation: Decomposers break down dead matter and release nutrients
back into the soil.
Q8.
Which of these is not a trophic level?
A. Producer
B. Consumer
C. Decomposer
D. Abiotic factor
Answer:
D. Abiotic factor
Explanation: Abiotic factors are non-living, not a trophic level.
Q9.
Which ecosystem component determines its structure and productivity?
A. Biotic
B. Abiotic
C. Consumers
D. Decomposers
Answer:
B. Abiotic
Explanation: Physical and chemical factors like light, water, and
temperature influence the ecosystem.
Q10.
An example of an artificial ecosystem is:
A. Pond
B. Garden
C. Ocean
D. Forest
Answer:
B. Garden
Explanation: Artificial ecosystems are man-made.
11–20: Food Chain & Food Web
Q11.
The sequence of organisms through which energy flows in an ecosystem is called:
A. Food web
B. Food chain
C. Pyramid
D. Biomass
Answer:
B. Food chain
Explanation: Energy flows linearly from producer → consumer →
decomposer.
Q12.
A food web is:
A. A single chain
B. Multiple interconnected food chains
C. Only producers
D. Only consumers
Answer:
B. Multiple interconnected food chains
Explanation: A food web shows the complex interconnections of feeding
relationships.
Q13.
Grass → Grasshopper → Frog → Snake → Hawk. In this chain, the hawk is:
A. Primary consumer
B. Secondary consumer
C. Tertiary consumer
D. Producer
Answer:
C. Tertiary consumer
Explanation: The top carnivore consuming secondary consumers is the
tertiary consumer.
Q14.
Herbivores are:
A. Primary consumers
B. Secondary consumers
C. Producers
D. Decomposers
Answer:
A. Primary consumers
Explanation: They directly feed on producers.
Q15.
Carnivores that eat herbivores are:
A. Primary consumers
B. Secondary consumers
C. Producers
D. Decomposers
Answer:
B. Secondary consumers
Explanation: They feed on primary consumers.
Q16.
Omnivores:
A. Eat only plants
B. Eat only animals
C. Eat both plants and animals
D. Only decompose organic matter
Answer:
C. Eat both plants and animals
Explanation: Omnivores like humans consume both producers and consumers.
Q17.
Which pyramid is always upright?
A. Pyramid of numbers
B. Pyramid of biomass
C. Pyramid of energy
D. Pyramid of productivity
Answer:
C. Pyramid of energy
Explanation: Energy decreases at each trophic level, so the pyramid is
always upright.
Q18.
In a pyramid of numbers, which can be inverted?
A. Tree ecosystem
B. Grassland ecosystem
C. Pond ecosystem
D. Desert ecosystem
Answer:
C. Pond ecosystem
Explanation: Few producers (large phytoplankton) support many consumers.
Q19.
Energy flow in an ecosystem is:
A. Cyclic
B. One-way
C. Bi-directional
D. Non-linear
Answer:
B. One-way
Explanation: Solar energy flows from producers to consumers and
decomposers.
Q20.
Which law describes energy transfer efficiency in trophic levels?
A. Newton’s Law
B. Liebig’s Law
C. 10% Law (Lindeman)
D. Law of Conservation
Answer:
C. 10% Law (Lindeman)
Explanation: Only ~10% of energy is transferred to the next trophic
level.
21–30: Ecological Succession
Q21.
Succession is:
A. Random change in community
B. Gradual predictable change
C. Sudden change
D. None
Answer:
B. Gradual predictable change
Explanation: Succession leads to a climax community.
Q22.
Primary succession occurs:
A. On bare rock
B. After fire
C. In cultivated land
D. In ponds
Answer:
A. On bare rock
Explanation: Pioneer species colonize lifeless areas.
Q23.
Secondary succession occurs:
A. On bare rock
B. In disturbed areas with soil
C. On water surface
D. In deserts
Answer:
B. In disturbed areas with soil
Explanation: Ecosystem regenerates where soil is already present.
Q24.
Climax community is:
A. Unstable
B. Mature and self-sustaining
C. Pioneer species
D. Artificial
Answer:
B. Mature and self-sustaining
Explanation: Stable, balanced community at the end of succession.
Q25.
Pioneer species in primary succession are usually:
A. Trees
B. Lichens and mosses
C. Shrubs
D. Animals
Answer:
B. Lichens and mosses
Explanation: They can survive harsh, bare environments.
Q26.
Example of secondary succession:
A. Bare rock → lichens
B. Abandoned farmland → grass → shrubs → trees
C. Ocean colonization
D. Pond formation
Answer:
B. Abandoned farmland → grass → shrubs → trees
Explanation: Soil is present; ecosystem regrows.
Q27.
Which is the correct sequence in primary succession?
A. Moss → Lichen → Grass → Shrub → Tree
B. Lichen → Moss → Grass → Shrub → Tree
C. Shrub → Moss → Grass → Tree → Lichen
D. Grass → Shrub → Tree → Lichen → Moss
Answer:
B. Lichen → Moss → Grass → Shrub → Tree
Explanation: Lichens colonize first, followed by moss, grass, shrubs,
then trees.
Q28.
Succession leads to:
A. Decline in productivity
B. Climax community
C. Extinction
D. Deforestation
Answer:
B. Climax community
Explanation: Ecosystem stabilizes at climax.
Q29.
Which factor controls succession?
A. Climate
B. Soil nutrients
C. Light availability
D. All of the above
Answer:
D. All of the above
Explanation: Abiotic factors influence species replacement.
Q30.
Which succession occurs in a newly formed volcanic island?
A. Secondary
B. Primary
C. Aquatic
D. None
Answer:
B. Primary
Explanation: No soil initially; pioneer species colonize bare rock.
31–50: Productivity & Energy
Flow
Q31.
Gross Primary Productivity (GPP) is:
A. Energy available to consumers
B. Total energy produced by producers
C. Energy lost in respiration
D. Energy lost in decomposition
Answer:
B. Total energy produced by producers
Explanation: GPP is total energy captured via photosynthesis by
producers.
Q32.
Net Primary Productivity (NPP) is:
A. GPP – Respiration
B. GPP + Respiration
C. Energy at tertiary level
D. Energy recycled by decomposers
Answer:
A. GPP – Respiration
Explanation: NPP is the energy available to consumers after producer
respiration.
Q33.
Secondary productivity refers to:
A. Energy in producers
B. Energy in herbivores and carnivores
C. Energy in decomposers
D. Solar energy
Answer:
B. Energy in herbivores and carnivores
Explanation: Energy stored in consumers is secondary productivity.
Q34.
Which factor does not affect ecosystem productivity?
A. Light intensity
B. Soil nutrients
C. Predator population
D. Temperature
Answer:
C. Predator population
Explanation: Abiotic factors primarily control productivity.
Q35.
The direction of energy flow in an ecosystem is:
A. Cyclic
B. One-way
C. Bi-directional
D. Random
Answer:
B. One-way
Explanation: Energy flows from producers → consumers → decomposers; it
is not recycled.
Q36.
Lindeman’s 10% law states:
A. Only 10% of energy is lost per trophic level
B. Only 10% of energy is transferred to next trophic level
C. 10% of consumers are carnivores
D. 10% of biomass is decomposed
Answer:
B. Only 10% of energy is transferred to next trophic level
Explanation: Most energy is lost as heat; only 10% is available to the
next level.
Q37.
Which pyramid may be inverted in some ecosystems?
A. Energy pyramid
B. Pyramid of numbers
C. Pyramid of biomass
D. All pyramids
Answer:
B. Pyramid of numbers
Explanation: Inverted when few large producers support many small
consumers (e.g., tree ecosystem).
Q38.
Pyramid of energy is always:
A. Inverted
B. Upright
C. Sometimes inverted
D. None
Answer:
B. Upright
Explanation: Energy decreases at each trophic level.
Q39.
In grassland ecosystem, primary productivity is maximum in:
A. Winter
B. Summer
C. Rainy season
D. Autumn
Answer:
C. Rainy season
Explanation: High rainfall → more photosynthesis → higher productivity.
Q40.
NPP = 1000 kcal/m²/year, Respiration = 400 kcal/m²/year. Then GPP = ?
A. 400
B. 600
C. 1400
D. 1000
Answer:
C. 1400 kcal/m²/year
Explanation: GPP = NPP + Respiration = 1000 + 400 = 1400.
Q41.
Net primary productivity is maximum in:
A. Ocean
B. Tropical forest
C. Desert
D. Arctic tundra
Answer:
B. Tropical forest
Explanation: Tropical forests have high sunlight, rainfall, and
nutrients.
Q42.
Ocean productivity is low due to:
A. Low light penetration
B. Nutrient limitation
C. Large water volume
D. All of the above
Answer:
D. All of the above
Explanation: Light, nutrients, and dilution limit productivity.
Q43.
Ecosystem efficiency depends on:
A. Energy transfer
B. Biomass distribution
C. Decomposer activity
D. All of the above
Answer:
D. All of the above
Explanation: Energy flow, biomass, and decomposition regulate ecosystem
efficiency.
Q44.
Decomposers recycle:
A. Carbon
B. Nitrogen
C. Phosphorus
D. All of the above
Answer:
D. All of the above
Explanation: Decomposers release nutrients from dead matter to soil and
water.
Q45.
Energy stored in autotrophs per unit area per unit time is:
A. GPP
B. NPP
C. Secondary productivity
D. Net energy
Answer:
A. GPP
Explanation: Gross primary productivity is total energy fixed by
photosynthesis.
Q46.
Aquatic ecosystems show inverted pyramids of:
A. Numbers
B. Energy
C. Biomass
D. All
Answer:
A. Numbers
Explanation: Few producers (phytoplankton) support many consumers.
Q47.
Decomposition rate is fastest in:
A. Desert
B. Tropical forest
C. Tundra
D. Grassland
Answer:
B. Tropical forest
Explanation: Warm, moist conditions enhance microbial activity.
Q48.
Which of the following is NOT a factor in energy flow?
A. Sunlight
B. Trophic efficiency
C. Predator-prey ratio
D. Nutrient recycling
Answer:
C. Predator-prey ratio
Explanation: Energy flow is controlled by producers, consumers, and
decomposers, not ratios.
Q49.
Energy transfer in food chain is:
A. Reversible
B. Unidirectional
C. Cyclic
D. Random
Answer:
B. Unidirectional
Explanation: Energy moves one-way from sun → producers → consumers →
decomposers.
Q50.
NPP is zero in:
A. Desert
B. Climax forest
C. Grassland
D. Tundra
Answer:
A. Desert
Explanation: Minimal productivity due to lack of water and vegetation.
51–70: Biogeochemical Cycles
Q51.
Carbon is fixed by:
A. Decomposers
B. Autotrophs
C. Carnivores
D. Omnivores
Answer:
B. Autotrophs
Explanation: Plants use CO₂ in photosynthesis to produce organic
compounds.
Q52.
Nitrogen fixation is performed by:
A. Fungi
B. Bacteria
C. Plants
D. Animals
Answer:
B. Bacteria
Explanation: Rhizobium in legume roots converts N₂ to NH₃.
Q53.
Phosphorus cycle does not include:
A. Atmosphere
B. Soil
C. Plants
D. Animals
Answer:
A. Atmosphere
Explanation: Phosphorus does not have a gaseous phase.
Q54.
Denitrification converts:
A. NO₃⁻ → N₂
B. N₂ → NH₃
C. NH₃ → NO₂⁻
D. NO₂⁻ → NH₃
Answer:
A. NO₃⁻ → N₂
Explanation: Denitrifying bacteria release nitrogen back to the
atmosphere.
Q55.
Largest carbon reservoir is:
A. Soil
B. Ocean
C. Fossil fuels
D. Atmosphere
Answer:
B. Ocean
Explanation: Oceans store more carbon than atmosphere or terrestrial ecosystems.
Q56.
Nitrification converts:
A. NH₄⁺ → NO₂⁻ → NO₃⁻
B. NO₃⁻ → N₂
C. N₂ → NH₃
D. NO₂⁻ → NH₄⁺
Answer:
A. NH₄⁺ → NO₂⁻ → NO₃⁻
Explanation: Nitrifying bacteria perform this conversion in soil.
Q57.
Ammonification is:
A. Conversion of organic nitrogen → NH₃
B. Conversion of NO₃⁻ → N₂
C. Nitrogen fixation
D. Phosphate release
Answer:
A. Conversion of organic nitrogen → NH₃
Explanation: Decomposers release ammonia from dead organic matter.
Q58.
Water cycle is also called:
A. Hydrological cycle
B. Carbon cycle
C. Nitrogen cycle
D. Phosphorus cycle
Answer:
A. Hydrological cycle
Explanation: Water evaporates → condenses → precipitates → runs off.
Q59.
Which cycle is affected by deforestation?
A. Carbon
B. Nitrogen
C. Water
D. All
Answer:
D. All
Explanation: Deforestation affects carbon storage, nitrogen fixation,
and precipitation patterns.
Q60.
Largest phosphorus reservoir:
A. Soil
B. Rocks
C. Water
D. Atmosphere
Answer:
B. Rocks
Explanation: Phosphorus mainly comes from weathering of phosphate rocks.
61–70: Aquatic Ecosystems
Q61.
The most productive aquatic ecosystem is:
A. Ocean
B. Estuary
C. Open sea
D. Deep ocean
Answer:
B. Estuary
Explanation: High nutrient input from rivers + shallow waters → high
productivity.
Q62.
Which zone in a lake is rich in light and nutrients?
A. Profundal
B. Littoral
C. Benthic
D. Aphotic
Answer:
B. Littoral
Explanation: Near shore, receives sunlight → supports photosynthesis.
Q63.
Phytoplankton are:
A. Primary consumers
B. Producers
C. Decomposers
D. Secondary consumers
Answer:
B. Producers
Explanation: Microscopic autotrophs, base of aquatic food chains.
Q64.
Zooplankton are:
A. Producers
B. Primary consumers
C. Secondary consumers
D. Decomposers
Answer:
B. Primary consumers
Explanation: Feed on phytoplankton.
Q65.
Open ocean productivity is low because:
A. Light is limited
B. Nutrients are scarce
C. Large water volume
D. All of the above
Answer:
D. All of the above
Explanation: Limited light and nutrients reduce photosynthesis.
Q66.
Coral reefs are found in:
A. Deep oceans
B. Shallow warm waters
C. Polar seas
D. Freshwater lakes
Answer:
B. Shallow warm waters
Explanation: Sunlight and warm temperatures favor coral growth.
Q67.
Eutrophication is caused by:
A. Excess nutrient input
B. Depletion of oxygen
C. High algal growth
D. All of the above
Answer:
D. All of the above
Explanation: Excess fertilizers → algal bloom → oxygen depletion → fish
death.
Q68.
Benthos are:
A. Floating organisms
B. Bottom-dwelling organisms
C. Surface swimmers
D. Producers
Answer:
B. Bottom-dwelling organisms
Explanation: Benthos live on or in the substrate of water bodies.
Q69.
Example of freshwater ecosystem:
A. Pond
B. Sea
C. Ocean
D. Coral reef
Answer:
A. Pond
Explanation: Pond, lake, river → freshwater ecosystem.
Q70.
Example of marine ecosystem:
A. River
B. Ocean
C. Pond
D. Lake
Answer:
B. Ocean
Explanation: Oceans, seas, estuaries → marine ecosystems.
71–80: Terrestrial Ecosystems
Q71.
Tropical rainforest is found in:
A. 0–23° N/S
B. 30–40° N
C. 50–60° N
D. Polar regions
Answer:
A. 0–23° N/S
Explanation: Warm temperature + high rainfall → tropical rainforest.
Q72.
Desert vegetation is mostly:
A. Dense trees
B. Succulents and xerophytes
C. Mosses and lichens
D. Aquatic plants
Answer:
B. Succulents and xerophytes
Explanation: Adapted to arid conditions with water storage.
Q73.
Tundra biome has:
A. High productivity
B. Permafrost soil
C. Dense forests
D. Grasslands
Answer:
B. Permafrost soil
Explanation: Frozen soil with low productivity and low plant cover.
Q74.
Temperate grasslands are dominated by:
A. Trees
B. Shrubs
C. Grasses
D. Mosses
Answer:
C. Grasses
Explanation: Moderate rainfall supports grass-dominated landscapes.
Q75.
Boreal forest is also called:
A. Taiga
B. Savanna
C. Chaparral
D. Tundra
Answer:
A. Taiga
Explanation: Coniferous forests in high latitudes.
Q76.
Forest ecosystem has:
A. High biodiversity
B. Multiple trophic levels
C. Dense canopy
D. All of the above
Answer:
D. All of the above
Explanation: Complex, multi-layered ecosystem.
Q77.
Grassland ecosystem productivity is:
A. High
B. Moderate
C. Low
D. Zero
Answer:
B. Moderate
Explanation: Moderate rainfall → supports grasses but fewer trees.
Q78.
Shrublands are adapted to:
A. Cold and wet climate
B. Hot and dry climate
C. Aquatic conditions
D. Tropical rainforest
Answer:
B. Hot and dry climate
Explanation: Shrubs are drought-resistant plants.
Q79.
Example of temperate deciduous forest:
A. Amazon
B. Oak forest of Europe
C. Siberian Taiga
D. Sahara Desert
Answer:
B. Oak forest of Europe
Explanation: Moderate climate, trees shed leaves seasonally.
Q80.
Chaparral is found in:
A. Mediterranean region
B. Polar region
C. Tropical rainforest
D. Grassland
Answer:
A. Mediterranean region
Explanation: Shrubland with dry summers and wet winters.
81–90: Human Impact on Ecosystems
Q81.
Deforestation leads to:
A. Soil erosion
B. Biodiversity loss
C. Climate change
D. All of the above
Answer:
D. All of the above
Explanation: Trees maintain soil, carbon cycle, and local climate.
Q82.
Overexploitation of resources causes:
A. Species extinction
B. Habitat loss
C. Ecological imbalance
D. All of the above
Answer:
D. All of the above
Explanation: Unsustainable use disrupts ecosystems.
Q83.
Global warming is mainly caused by:
A. Depletion of ozone
B. Greenhouse gases
C. Deforestation
D. Both B and C
Answer:
D. Both B and C
Explanation: CO₂ and deforestation increase global temperatures.
Q84.
Biological magnification refers to:
A. Decrease of toxins along food chain
B. Increase of toxin concentration at higher trophic levels
C. Energy flow in food chain
D. Nutrient cycling
Answer:
B. Increase of toxin concentration at higher trophic levels
Explanation: Persistent pollutants accumulate in top predators.
Q85.
Eutrophication results in:
A. Increased oxygen
B. Algal bloom
C. Reduced organic matter
D. Decreased nutrients
Answer:
B. Algal bloom
Explanation: Excess nutrients → algal growth → oxygen depletion.
Q86.
Acid rain is caused by:
A. CO₂
B. SO₂ and NO₂
C. O₂
D. N₂
Answer:
B. SO₂ and NO₂
Explanation: Sulfur and nitrogen oxides react with rain → acidic
precipitation.
Q87.
Which is a renewable resource?
A. Coal
B. Petroleum
C. Sunlight
D. Natural gas
Answer:
C. Sunlight
Explanation: Renewable resources replenish naturally.
Q88.
Overgrazing leads to:
A. Soil fertility increase
B. Desertification
C. Forest growth
D. Increased rainfall
Answer:
B. Desertification
Explanation: Loss of vegetation → soil erosion → land degradation.
Q89.
Ozone layer depletion causes:
A. Increased UV radiation
B. Global warming
C. Deforestation
D. Eutrophication
Answer:
A. Increased UV radiation
Explanation: UV rays damage DNA and ecosystems.
Q90.
Human activities that disturb ecosystems:
A. Urbanization
B. Industrialization
C. Agriculture
D. All of the above
Answer:
D. All of the above
Explanation: Land-use changes and pollution disrupt ecosystems.
91–100: Conservation &
NEET-focused Concepts
Q91.
Biodiversity hotspots are regions with:
A. High species richness
B. Low endemism
C. Low productivity
D. Desert conditions
Answer:
A. High species richness
Explanation: Areas with high diversity and endemic species.
Q92.
National parks are meant for:
A. Tourism
B. Wildlife conservation
C. Agriculture
D. Mining
Answer:
B. Wildlife conservation
Explanation: Strictly protected to conserve biodiversity.
Q93.
Biosphere reserves aim to:
A. Conserve species
B. Promote sustainable development
C. Both A and B
D. Only agriculture
Answer:
C. Both A and B
Explanation: Zones for core conservation, buffer, and transition.
Q94.
Afforestation is:
A. Cutting trees
B. Planting trees in barren land
C. Soil erosion
D. Urbanization
Answer:
B. Planting trees in barren land
Explanation: Increases forest cover and ecological balance.
Q95.
EDGE species are:
A. Extinct species
B. Endangered species
C. Endangered + Evolutionarily Distinct species
D. Exotic species
Answer:
C. Endangered + Evolutionarily Distinct species
Explanation: Unique species at risk of extinction.
Q96.
Bioremediation uses:
A. Microorganisms to degrade pollutants
B. Chemicals to kill pests
C. Artificial energy
D. Physical barriers
Answer:
A. Microorganisms to degrade pollutants
Explanation: Bacteria and fungi clean up oil spills, sewage, etc.
Q97.
REDD program relates to:
A. Forest conservation
B. Soil fertility
C. Water purification
D. Marine biodiversity
Answer:
A. Forest conservation
Explanation: Reducing Emissions from Deforestation and Forest
Degradation.
Q98.
CITES is an international treaty to:
A. Protect endangered species
B. Control pollution
C. Prevent forest fires
D. Promote tourism
Answer:
A. Protect endangered species
Explanation: Controls trade of threatened species.
Q99.
Biodiversity conservation ensures:
A. Genetic diversity
B. Ecological balance
C. Sustainable resource use
D. All of the above
Answer:
D. All of the above
Explanation: Maintains ecosystem stability and human welfare.
Q100.
Keystone species are:
A. Most abundant species
B. Species whose removal affects ecosystem significantly
C. Primary producers only
D. Decomposers only
Answer:
B. Species whose removal affects ecosystem significantly
Explanation: Their presence maintains ecosystem structure.
