Complete Ecosystem Question Bank & Solutions (106 Questions)
Q1 of 106
NEET NCERT Line-by-Line
An ecosystem is best defined as:
(A)
The vertical layering of plants in a forest
(B)
A community of plants only
(C)
A group of organisms of the same species
(D)
A functional unit of nature where organisms interact among themselves and with the physical environment
Show Answer & NCERT Explanation
Correct Answer: (D) A functional unit of nature where organisms interact among themselves and with the physical environment
It is a functional unit of nature — the interaction is both among organisms AND with the physical environment.
Q2 of 106
NEET NCERT Line-by-Line
Which of the following is a TERRESTRIAL ecosystem?
(A)
Lake
(B)
Estuary
(C)
Wetland
(D)
Grassland
Show Answer & NCERT Explanation
Correct Answer: (D) Grassland
NCERT's terrestrial examples: forest, grassland, desert. Estuary, wetland and lake are aquatic.
Q3 of 106
NEET NCERT Line-by-Line
Which of these is a MAN-MADE ecosystem?
(A)
Aquarium
(B)
Desert
(C)
Wetland
(D)
Estuary
Show Answer & NCERT Explanation
Correct Answer: (A) Aquarium
Crop fields and an aquarium may be considered man-made ecosystems.
Q4 of 106
NEET NCERT Line-by-Line
The vertical distribution of different species occupying different levels is called:
(A)
Zonation
(B)
Stratification
(C)
Standing crop
(D)
Species composition
Show Answer & NCERT Explanation
Correct Answer: (B) Stratification
Stratification. In a forest: trees on top, shrubs second, herbs and grasses at the bottom.
Q5 of 106
NEET NCERT Line-by-Line
Identification and enumeration of plant and animal species of an ecosystem gives its:
(A)
Productivity
(B)
Stratification
(C)
Species composition
(D)
Standing crop
Show Answer & NCERT Explanation
Correct Answer: (C) Species composition
Species composition — one of the two structural features of an ecosystem.
Q6 of 106
NEET NCERT Line-by-Line
Which layer of a forest do shrubs occupy?
(A)
The bottom layer
(B)
Below the soil
(C)
The top strata
(D)
The second layer
Show Answer & NCERT Explanation
Correct Answer: (D) The second layer
Trees = top strata; shrubs = second; herbs and grasses = bottom layers.
Q7 of 106
NEET NCERT Line-by-Line
Which of the following is NOT one of the four functional aspects of an ecosystem?
(A)
Stratification
(B)
Energy flow
(C)
Productivity
(D)
Decomposition
Show Answer & NCERT Explanation
Correct Answer: (A) Stratification
Stratification is a STRUCTURAL feature, not a functional aspect. The four functions are productivity, decomposition, energy flow and nutrient cycling.
Q8 of 106
NEET NCERT Line-by-Line
The abiotic components of an ecosystem are:
(A)
Producers, consumers and decomposers
(B)
Air, water and soil
(C)
Herbivores and carnivores
(D)
Fungi and bacteria
Show Answer & NCERT Explanation
Correct Answer: (B) Air, water and soil
Abiotic = inorganic materials: air, water and soil. Biotic = producers, consumers, decomposers.
Q9 of 106
NEET NCERT Line-by-Line
In a pond, which organisms are especially abundant at the BOTTOM?
(A)
Phytoplankton
(B)
Free-swimming forms
(C)
Fungi, bacteria and flagellates
(D)
Marginal plants
Show Answer & NCERT Explanation
Correct Answer: (C) Fungi, bacteria and flagellates
The decomposers — fungi, bacteria and flagellates — are especially abundant at the bottom of the pond.
Q10 of 106
NEET NCERT Line-by-Line
The abiotic component of a pond includes:
(A)
Only the phytoplankton
(B)
The zooplankton and free-swimming forms
(C)
Only the water
(D)
The water with dissolved inorganic and organic substances, plus the rich soil deposit at the bottom
Show Answer & NCERT Explanation
Correct Answer: (D) The water with dissolved inorganic and organic substances, plus the rich soil deposit at the bottom
It includes both the water with all dissolved substances AND the rich bottom soil deposit.
Q11 of 106
NEET NCERT Line-by-Line
Which of these regulates the rate of function of the entire pond?
(A)
Solar input, temperature cycle, day-length and climatic conditions
(B)
The number of zooplankton
(C)
The depth of the soil deposit
(D)
The species of fungi present
Show Answer & NCERT Explanation
Correct Answer: (A) Solar input, temperature cycle, day-length and climatic conditions
NCERT lists exactly these: solar input, cycle of temperature, day-length and other climatic conditions.
Q12 of 106
NEET NCERT Line-by-Line
The autotrophic components of a pond include:
(A)
Fungi, bacteria and flagellates
(B)
Phytoplankton, algae and floating/submerged/marginal plants
(C)
Free-swimming fish
(D)
Zooplankton and bottom dwellers
Show Answer & NCERT Explanation
Correct Answer: (B) Phytoplankton, algae and floating/submerged/marginal plants
Phytoplankton, some algae, and the floating, submerged and marginal plants at the edges.
Q13 of 106
NEET NCERT Line-by-Line
Primary PRODUCTION is expressed in units of:
(A)
kcal only
(B)
kg ha⁻¹ day⁻¹
(C)
g m⁻² or kcal m⁻²
(D)
g m⁻² yr⁻¹ only
Show Answer & NCERT Explanation
Correct Answer: (C) g m⁻² or kcal m⁻²
Production is an AMOUNT: g m−2 (weight) or kcal m−2 (energy). Productivity is a RATE and carries yr−1.
Q14 of 106
NEET NCERT Line-by-Line
Productivity is expressed as:
(A)
tons only
(B)
g m⁻²
(C)
kcal m⁻²
(D)
g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹
Show Answer & NCERT Explanation
Correct Answer: (D) g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹
Productivity is a RATE — hence the yr−1 — so that different ecosystems can be compared.
Q15 of 106
NEET NCERT Line-by-Line
Gross Primary Productivity (GPP) is:
(A)
The rate of production of organic matter during photosynthesis
(B)
The biomass left after respiration
(C)
The rate of formation of organic matter by consumers
(D)
The energy lost as heat
Show Answer & NCERT Explanation
Correct Answer: (A) The rate of production of organic matter during photosynthesis
GPP = the rate of production of organic matter during photosynthesis. A considerable part of it is used in respiration.
Q16 of 106
NEET NCERT Line-by-Line
The correct formula for net primary productivity is:
(A)
NPP = GPP + R
(B)
NPP = GPP − R
(C)
GPP = NPP − R
(D)
NPP = R − GPP
Show Answer & NCERT Explanation
Correct Answer: (B) NPP = GPP − R
GPP − R = NPP. Think: earn minus spend equals keep.
Q17 of 106
NEET NCERT Line-by-Line
Net primary productivity is the biomass available for consumption by:
(A)
Herbivores only
(B)
Carnivores only
(C)
Herbivores and decomposers
(D)
Producers
Show Answer & NCERT Explanation
Correct Answer: (C) Herbivores and decomposers
NPP is available to heterotrophs — herbivores AND decomposers. 'Herbivores only' is the classic trap.
Q18 of 106
NEET NCERT Line-by-Line
Secondary productivity is defined as:
(A)
GPP minus respiration
(B)
The rate of decomposition
(C)
The rate of production of organic matter during photosynthesis
(D)
The rate of formation of new organic matter by CONSUMERS
Show Answer & NCERT Explanation
Correct Answer: (D) The rate of formation of new organic matter by CONSUMERS
It refers to consumers, not producers.
Q19 of 106
NEET NCERT Line-by-Line
The annual net primary productivity of the whole biosphere is approximately:
(A)
55 billion tons
(B)
115 billion tons
(C)
170 billion tons
(D)
500 billion tons
Show Answer & NCERT Explanation
Correct Answer: (C) 170 billion tons
~170 billion tons (dry weight) of organic matter.
Q20 of 106
NEET NCERT Line-by-Line
The annual net primary productivity of the oceans is approximately:
(A)
55 billion tons
(B)
115 billion tons
(C)
170 billion tons
(D)
70 billion tons
Show Answer & NCERT Explanation
Correct Answer: (A) 55 billion tons
Only 55 billion tons — despite the oceans covering ~70% of the surface.
Q21 of 106
NEET NCERT Line-by-Line
Oceans occupy about what percentage of the Earth's surface?
(A)
70%
(B)
90%
(C)
50%
(D)
60%
Show Answer & NCERT Explanation
Correct Answer: (A) 70%
About 70 per cent — yet they contribute only 55 of the 170 billion tons of annual NPP.
Q22 of 106
NEET NCERT Line-by-Line
The limiting factor for productivity in aquatic ecosystems is:
(A)
Carbon dioxide
(B)
Light
(C)
Temperature
(D)
Oxygen
Show Answer & NCERT Explanation
Correct Answer: (B) Light
LIGHT. Sunlight penetrates only a thin upper layer, so photosynthesis is confined to a shallow film of water. (NCERT Exercise 1c.)
Q23 of 106
NEET NCERT Line-by-Line
Which of these does primary productivity NOT depend on?
(A)
Availability of nutrients
(B)
Photosynthetic capacity of plants
(C)
Number of top carnivores
(D)
Plant species inhabiting the area
Show Answer & NCERT Explanation
Correct Answer: (C) Number of top carnivores
NCERT lists: plant species, environmental factors, availability of nutrients, photosynthetic capacity.
Q24 of 106
NEET NCERT Line-by-Line
The earthworm is called the farmer's friend because it:
(A)
Photosynthesises in the soil
(B)
Kills soil pathogens
(C)
Fixes atmospheric nitrogen
(D)
Breaks down complex organic matter and loosens the soil
Show Answer & NCERT Explanation
Correct Answer: (D) Breaks down complex organic matter and loosens the soil
It is a detritivore — it fragments detritus and aerates/loosens the soil.
Q25 of 106
NEET NCERT Line-by-Line
Detritus consists of:
(A)
Dead plant remains, dead animal remains AND faecal matter
(B)
Only faecal matter
(C)
Only dead plant remains
(D)
Only dead animal remains
Show Answer & NCERT Explanation
Correct Answer: (A) Dead plant remains, dead animal remains AND faecal matter
Detritus = leaves, bark, flowers + dead animal remains INCLUDING faecal matter. It is the raw material for decomposition.
Q26 of 106
NEET NCERT Line-by-Line
The correct sequence of steps in decomposition is:
(A)
Leaching → Fragmentation → Catabolism → Mineralisation → Humification
(B)
Fragmentation → Leaching → Catabolism → Humification → Mineralisation
(C)
Catabolism → Fragmentation → Leaching → Humification → Mineralisation
(D)
Fragmentation → Catabolism → Leaching → Mineralisation → Humification
Show Answer & NCERT Explanation
Correct Answer: (B) Fragmentation → Leaching → Catabolism → Humification → Mineralisation
Fragmentation → Leaching → Catabolism → Humification → Mineralisation. Mnemonic: 'Fresh Leaves Cook, Humus Made'.
Q27 of 106
NEET NCERT Line-by-Line
Breaking down of detritus into smaller particles by detritivores is called:
(A)
Catabolism
(B)
Leaching
(C)
Fragmentation
(D)
Humification
Show Answer & NCERT Explanation
Correct Answer: (C) Fragmentation
Fragmentation — e.g., by the earthworm.
Q28 of 106
NEET NCERT Line-by-Line
In leaching, water-soluble inorganic nutrients:
(A)
Evaporate into the atmosphere
(B)
Are converted into humus
(C)
Are absorbed by plants immediately
(D)
Go down into the soil horizon and get precipitated as UNAVAILABLE salts
Show Answer & NCERT Explanation
Correct Answer: (D) Go down into the soil horizon and get precipitated as UNAVAILABLE salts
The key word is UNAVAILABLE — leaching makes nutrients inaccessible, it does not release them.
Q29 of 106
NEET NCERT Line-by-Line
Degradation of detritus into simpler inorganic substances by bacterial and fungal enzymes is called:
(A)
Catabolism
(B)
Mineralisation
(C)
Fragmentation
(D)
Leaching
Show Answer & NCERT Explanation
Correct Answer: (A) Catabolism
Catabolism — driven by bacterial and fungal ENZYMES.
Q30 of 106
NEET NCERT Line-by-Line
Humus is:
(A)
A crystalline mineral salt
(B)
A dark-coloured amorphous substance, highly resistant to microbial action
(C)
A rapidly decomposing sugar
(D)
A gaseous product of decomposition
Show Answer & NCERT Explanation
Correct Answer: (B) A dark-coloured amorphous substance, highly resistant to microbial action
Dark, amorphous, highly resistant, decomposes extremely slowly, colloidal, and serves as a reservoir of nutrients.
Q31 of 106
NEET NCERT Line-by-Line
Humus serves as a reservoir of nutrients because it is:
(A)
Highly soluble
(B)
Crystalline
(C)
Colloidal in nature
(D)
Gaseous
Show Answer & NCERT Explanation
Correct Answer: (C) Colloidal in nature
Being colloidal, it holds and slowly releases nutrients.
Q32 of 106
NEET NCERT Line-by-Line
The release of inorganic nutrients from humus by microbes is called:
(A)
Leaching
(B)
Fragmentation
(C)
Humification
(D)
Mineralisation
Show Answer & NCERT Explanation
Correct Answer: (D) Mineralisation
Mineralisation. Humification builds humus; mineralisation breaks it down and releases nutrients.
Q33 of 106
NEET NCERT Line-by-Line
Which two steps of decomposition occur IN THE SOIL?
(A)
Humification and mineralisation
(B)
Leaching and catabolism
(C)
Fragmentation and leaching
(D)
Catabolism and fragmentation
Show Answer & NCERT Explanation
Correct Answer: (A) Humification and mineralisation
NCERT: 'Humification and mineralisation occur during decomposition in the soil.'
Q34 of 106
NEET NCERT Line-by-Line
The steps of decomposition:
(A)
Occur strictly one after the other
(B)
All operate SIMULTANEOUSLY on the detritus
(C)
Occur only in winter
(D)
Occur only in anaerobic conditions
Show Answer & NCERT Explanation
Correct Answer: (B) All operate SIMULTANEOUSLY on the detritus
NCERT is explicit: all the steps operate simultaneously.
Q35 of 106
NEET NCERT Line-by-Line
Decomposition is largely a/an:
(A)
Nitrogen-requiring process
(B)
Anaerobic process
(C)
Oxygen-requiring process
(D)
Light-requiring process
Show Answer & NCERT Explanation
Correct Answer: (C) Oxygen-requiring process
Decomposition is largely an OXYGEN-REQUIRING process.
Q36 of 106
NEET NCERT Line-by-Line
Decomposition is SLOWER if the detritus is rich in:
(A)
Water-soluble substances
(B)
Nitrogen
(C)
Sugars
(D)
Lignin and chitin
Show Answer & NCERT Explanation
Correct Answer: (D) Lignin and chitin
Lignin and chitin slow it down. Nitrogen and sugars speed it up.
Q37 of 106
NEET NCERT Line-by-Line
Decomposition is QUICKER if the detritus is rich in:
(A)
Nitrogen and water-soluble substances like sugars
(B)
Cellulose only
(C)
Lignin
(D)
Chitin
Show Answer & NCERT Explanation
Correct Answer: (A) Nitrogen and water-soluble substances like sugars
Nitrogen and water-soluble sugars accelerate microbial breakdown.
Q38 of 106
NEET NCERT Line-by-Line
The two most important CLIMATIC factors regulating decomposition are:
(A)
Light and wind
(B)
Temperature and soil moisture
(C)
Rainfall and altitude
(D)
Pressure and salinity
Show Answer & NCERT Explanation
Correct Answer: (B) Temperature and soil moisture
Temperature and soil moisture — through their effects on the activities of soil microbes.
Q39 of 106
NEET NCERT Line-by-Line
Which conditions INHIBIT decomposition, causing a build-up of organic material?
(A)
Neutral pH and moderate rain
(B)
Warm and moist conditions
(C)
Low temperature and anaerobiosis
(D)
High oxygen and high nitrogen
Show Answer & NCERT Explanation
Correct Answer: (C) Low temperature and anaerobiosis
Low temperature + anaerobiosis inhibit decomposition → organic material accumulates (this is how peat forms).
Q40 of 106
NEET NCERT Line-by-Line
Which ecosystem is NOT dependent on the sun as its energy source?
(A)
Desert
(B)
Tropical rainforest
(C)
Coral reef
(D)
Deep-sea hydro-thermal ecosystem
Show Answer & NCERT Explanation
Correct Answer: (D) Deep-sea hydro-thermal ecosystem
The deep-sea hydro-thermal ecosystem is NCERT's single stated exception.
Q41 of 106
NEET NCERT Line-by-Line
What percentage of the incident solar radiation is photosynthetically active radiation (PAR)?
(A)
Less than 50%
(B)
2–10%
(C)
1%
(D)
10%
Show Answer & NCERT Explanation
Correct Answer: (A) Less than 50%
Less than 50% of incident solar radiation is PAR. (2–10% is the fraction of PAR that is CAPTURED — the classic trap.)
Q42 of 106
NEET NCERT Line-by-Line
What percentage of the PAR do plants actually capture?
(A)
100%
(B)
2–10%
(C)
25%
(D)
50%
Show Answer & NCERT Explanation
Correct Answer: (B) 2–10%
Only 2–10% of the PAR — and this small amount of energy sustains the entire living world.
Q43 of 106
NEET NCERT Line-by-Line
In an ideal pyramid of energy, primary producers convert what percentage of available sunlight into NPP?
(A)
10%
(B)
50%
(C)
1%
(D)
25%
Show Answer & NCERT Explanation
Correct Answer: (C) 1%
About 1 per cent.
Q44 of 106
NEET NCERT Line-by-Line
Ecosystems need a constant supply of energy in order to:
(A)
Create energy from nothing
(B)
Reverse the flow of nutrients
(C)
Violate the second law of thermodynamics
(D)
Counteract the universal tendency toward increasing disorderliness
Show Answer & NCERT Explanation
Correct Answer: (D) Counteract the universal tendency toward increasing disorderliness
Ecosystems are not exempt from the Second Law — they must fight entropy continuously.
Q45 of 106
NEET NCERT Line-by-Line
The major producers in a TERRESTRIAL ecosystem are:
(A)
Herbaceous and woody plants
(B)
Fungi and bacteria
(C)
Zooplankton
(D)
Phytoplankton and algae
Show Answer & NCERT Explanation
Correct Answer: (A) Herbaceous and woody plants
Herbaceous and woody plants. Phytoplankton/algae are aquatic producers.
Q46 of 106
NEET NCERT Line-by-Line
Common herbivores in an AQUATIC ecosystem are:
(A)
Birds
(B)
Molluscs
(C)
Mammals
(D)
Insects
Show Answer & NCERT Explanation
Correct Answer: (B) Molluscs
NCERT names molluscs as the aquatic herbivores; insects, birds and mammals are the terrestrial ones.
Q47 of 106
NEET NCERT Line-by-Line
In NCERT's grazing food chain 'Grass → Goat → Man', Man is a:
(A)
Secondary consumer
(B)
Decomposer
(C)
Producer
(D)
Primary consumer
Show Answer & NCERT Explanation
Correct Answer: (A) Secondary consumer
Grass = producer; goat = primary consumer; man = secondary consumer.
Q48 of 106
NEET NCERT Line-by-Line
A secondary consumer is more correctly called a:
(A)
Secondary carnivore
(B)
Producer
(C)
Herbivore
(D)
Primary carnivore
Show Answer & NCERT Explanation
Correct Answer: (D) Primary carnivore
Secondary consumer = primary carnivore. Tertiary consumer = secondary carnivore.
Q49 of 106
NEET NCERT Line-by-Line
The detritus food chain begins with:
(A)
Dead organic matter
(B)
Herbivores
(C)
Sunlight
(D)
Living green plants
Show Answer & NCERT Explanation
Correct Answer: (A) Dead organic matter
The DFC begins with dead organic matter (detritus).
Q50 of 106
NEET NCERT Line-by-Line
Saprotrophs are:
(A)
Herbivores
(B)
Decomposers — mainly fungi and bacteria
(C)
Top carnivores
(D)
Producers
Show Answer & NCERT Explanation
Correct Answer: (B) Decomposers — mainly fungi and bacteria
'Sapro' = to decompose. They are the heterotrophic decomposers of the DFC.
Q51 of 106
NEET NCERT Line-by-Line
How do decomposers obtain their nutrition?
(A)
By preying on herbivores
(B)
By ingesting whole food particles
(C)
By secreting digestive enzymes that break down dead material into simple inorganic materials, which they then ABSORB
(D)
By photosynthesis
Show Answer & NCERT Explanation
Correct Answer: (C) By secreting digestive enzymes that break down dead material into simple inorganic materials, which they then ABSORB
They digest externally and then absorb the products.
Q52 of 106
NEET NCERT Line-by-Line
In an AQUATIC ecosystem, the major conduit for energy flow is:
(A)
Chemosynthesis
(B)
Leaching
(C)
The detritus food chain
(D)
The grazing food chain
Show Answer & NCERT Explanation
Correct Answer: (D) The grazing food chain
GFC dominates in water. Memory hook: 'Water grazes, Land rots.'
Q53 of 106
NEET NCERT Line-by-Line
In a TERRESTRIAL ecosystem, a much larger fraction of energy flows through:
(A)
The detritus food chain
(B)
Photosynthesis
(C)
The pyramid of numbers
(D)
The grazing food chain
Show Answer & NCERT Explanation
Correct Answer: (A) The detritus food chain
DFC dominates on land. Most plant biomass is not eaten alive — it dies and is decomposed.
Q54 of 106
NEET NCERT Line-by-Line
Which animals does NCERT name as OMNIVORES that connect the GFC and DFC?
(A)
Goats and cattle
(B)
Cockroaches and crows
(C)
Tigers and lions
(D)
Earthworms and snails
Show Answer & NCERT Explanation
Correct Answer: (B) Cockroaches and crows
Cockroaches and crows. These natural interconnections make a food WEB.
Q55 of 106
NEET NCERT Line-by-Line
Producers, herbivores and carnivores belong respectively to which trophic levels?
(A)
Third, second, first
(B)
First, third, second
(C)
First, second, third
(D)
Second, first, third
Show Answer & NCERT Explanation
Correct Answer: (C) First, second, third
Producers = T1; herbivores (primary consumers) = T2; carnivores (secondary consumers) = T3.
Q56 of 106
NEET NCERT Line-by-Line
A trophic level represents:
(A)
A geographical zone
(B)
A taxonomic order
(C)
A single species
(D)
A functional level, NOT a species
Show Answer & NCERT Explanation
Correct Answer: (D) A functional level, NOT a species
A given species may occupy MORE THAN ONE trophic level in the same ecosystem at the same time.
Q57 of 106
NEET NCERT Line-by-Line
A sparrow eating insects and worms is functioning as a:
(A)
Producer
(B)
Primary consumer
(C)
Secondary consumer
(D)
Decomposer
Show Answer & NCERT Explanation
Correct Answer: (C) Secondary consumer
Eating seeds/fruits/peas → primary consumer. Eating insects and worms → secondary consumer.
Q58 of 106
NEET NCERT Line-by-Line
Standing crop is defined as:
(A)
The energy lost as heat at each trophic level
(B)
The mass of living material at a trophic level at a particular time
(C)
The rate of biomass production
(D)
The number of trophic levels in a food chain
Show Answer & NCERT Explanation
Correct Answer: (B) The mass of living material at a trophic level at a particular time
It is a snapshot of biomass (or number) per unit area at one moment — not a rate.
Q59 of 106
NEET NCERT Line-by-Line
Measurement of biomass in terms of DRY weight is more accurate because:
(A)
Fresh weight ignores the roots
(B)
Dry weight is easier to measure
(C)
Fresh weight varies with water content, which contributes no organic matter or energy
(D)
Dry weight includes the water
Show Answer & NCERT Explanation
Correct Answer: (C) Fresh weight varies with water content, which contributes no organic matter or energy
Water content fluctuates with hydration, humidity and species — it distorts comparisons.
Q60 of 106
NEET NCERT Line-by-Line
According to the 10 per cent law, if producers hold 20,000 J, the energy at the THIRD trophic level is:
(A)
2000 J
(B)
200 J
(C)
20 J
(D)
2 J
Show Answer & NCERT Explanation
Correct Answer: (B) 200 J
T1 = 20,000 J → T2 = 2,000 J → T3 = 200 J.
Q61 of 106
NEET NCERT Line-by-Line
The 10 per cent law explains why:
(A)
Decomposition is aerobic
(B)
Oceans have low productivity
(C)
Pyramids of biomass can be inverted
(D)
The number of trophic levels in a grazing food chain is restricted
Show Answer & NCERT Explanation
Correct Answer: (D) The number of trophic levels in a grazing food chain is restricted
After a few levels there simply isn't enough energy left to support another.
Q62 of 106
NEET NCERT Line-by-Line
The base of an ecological pyramid represents:
(A)
Producers (the first trophic level)
(B)
Decomposers
(C)
Herbivores
(D)
Top carnivores
Show Answer & NCERT Explanation
Correct Answer: (A) Producers (the first trophic level)
Base = producers. Apex = tertiary or top-level consumer.
Q63 of 106
NEET NCERT Line-by-Line
In a grassland ecosystem, nearly 6 million plants support how many top carnivores?
(A)
3
(B)
30
(C)
300
(D)
3000
Show Answer & NCERT Explanation
Correct Answer: (A) 3
Only three — NCERT's Figure 12.4(a).
Q64 of 106
NEET NCERT Line-by-Line
The pyramid of NUMBERS is inverted in which ecosystem?
(A)
Grassland
(B)
A tree ecosystem
(C)
The sea
(D)
A desert
Show Answer & NCERT Explanation
Correct Answer: (B) A tree ecosystem
A single big TREE supports many insects, which support fewer birds → inverted.
Q65 of 106
NEET NCERT Line-by-Line
The pyramid of BIOMASS is generally inverted in:
(A)
A forest
(B)
A grassland
(C)
The sea
(D)
A crop field
Show Answer & NCERT Explanation
Correct Answer: (C) The sea
In the sea, the biomass of fishes far exceeds that of phytoplankton.
Q66 of 106
NEET NCERT Line-by-Line
In an inverted pyramid of biomass in the sea:
(A)
There are no producers
(B)
Energy flows upward and downward
(C)
A large standing crop of phytoplankton supports a small standing crop of zooplankton
(D)
A small standing crop of phytoplankton supports a large standing crop of zooplankton
Show Answer & NCERT Explanation
Correct Answer: (D) A small standing crop of phytoplankton supports a large standing crop of zooplankton
A SMALL phytoplankton standing crop supports a LARGE zooplankton standing crop.
Q67 of 106
NEET NCERT Line-by-Line
Which pyramid can NEVER be inverted?
(A)
Pyramid of numbers
(B)
Pyramid of biomass
(C)
Pyramid of energy
(D)
All three can be inverted
Show Answer & NCERT Explanation
Correct Answer: (C) Pyramid of energy
The pyramid of ENERGY is always upright, because some energy is always lost as heat at each step.
Q68 of 106
NEET NCERT Line-by-Line
The reason the energy pyramid is always upright is that:
(A)
Some energy is always lost as heat at each transfer
(B)
Decomposers are excluded
(C)
Biomass is always higher at the base
(D)
Producers are always more numerous
Show Answer & NCERT Explanation
Correct Answer: (A) Some energy is always lost as heat at each transfer
The heat loss is inescapable — energy at a lower level is always more than at a higher level.
Q69 of 106
NEET NCERT Line-by-Line
Each bar in a pyramid of energy indicates:
(A)
The dry weight of organisms at that level
(B)
The amount of energy present at that trophic level in a given time or annually per unit area
(C)
The rate of decomposition
(D)
The number of individuals at that trophic level
Show Answer & NCERT Explanation
Correct Answer: (B) The amount of energy present at that trophic level in a given time or annually per unit area
Energy per unit area, per unit time.
Q70 of 106
NEET NCERT Line-by-Line
Which of the following is NOT a limitation of ecological pyramids?
(A)
They assume a simple food chain and cannot accommodate a food web
(B)
Saprophytes are not given any place
(C)
They cannot be drawn for terrestrial ecosystems
(D)
They do not account for a species belonging to two or more trophic levels
Show Answer & NCERT Explanation
Correct Answer: (C) They cannot be drawn for terrestrial ecosystems
The three real limitations are the three S's: Same species, Simple chain, Saprophytes skipped.
Q71 of 106
NEET NCERT Line-by-Line
Saprophytes are:
(A)
The same as producers
(B)
Placed at the apex of ecological pyramids
(C)
Placed at the base of ecological pyramids
(D)
Not given any place in ecological pyramids, despite playing a vital role
Show Answer & NCERT Explanation
Correct Answer: (D) Not given any place in ecological pyramids, despite playing a vital role
This is one of the three stated limitations of ecological pyramids.
Q72 of 106
NEET NCERT Line-by-Line
Nutrient cycling is defined as:
(A)
The storage and movement of nutrient elements through the various components of the ecosystem
(B)
The loss of nutrients as heat
(C)
The vertical layering of species
(D)
The unidirectional flow of energy
Show Answer & NCERT Explanation
Correct Answer: (A) The storage and movement of nutrient elements through the various components of the ecosystem
Through this process, nutrients are used repeatedly — unlike energy, which is lost.
Q73 of 106
NEET NCERT Line-by-Line
The reservoir for a GASEOUS nutrient cycle is:
(A)
The Earth's crust
(B)
The atmosphere or hydrosphere
(C)
The soil humus
(D)
The detritus layer
Show Answer & NCERT Explanation
Correct Answer: (B) The atmosphere or hydrosphere
Gaseous cycle (e.g., carbon) → reservoir = atmosphere or hydrosphere.
Q74 of 106
NEET NCERT Line-by-Line
The reservoir for a SEDIMENTARY nutrient cycle is:
(A)
The atmosphere
(B)
The hydrosphere
(C)
The Earth's crust
(D)
The biosphere
Show Answer & NCERT Explanation
Correct Answer: (C) The Earth's crust
Sedimentary cycle (e.g., phosphorus) → reservoir = Earth's crust. 'Carbon flies, Phosphorus lies.'
Q75 of 106
NEET NCERT Line-by-Line
Phosphorus follows which type of nutrient cycle?
(A)
Hydrological
(B)
Atmospheric
(C)
Gaseous
(D)
Sedimentary
Show Answer & NCERT Explanation
Correct Answer: (D) Sedimentary
Sedimentary — its reservoir is the Earth's crust.
Q76 of 106
NEET NCERT Line-by-Line
The major reservoir of carbon on Earth is:
(A)
The oceans
(B)
Fossil fuels
(C)
The atmosphere
(D)
Forests
Show Answer & NCERT Explanation
Correct Answer: (A) The oceans
The oceans. (NCERT Exercise 1e.)
Q77 of 106
NEET NCERT Line-by-Line
Ecosystem services are:
(A)
The trophic levels of a food web
(B)
The products of ecosystem processes
(C)
The four functional components of an ecosystem
(D)
The abiotic components
Show Answer & NCERT Explanation
Correct Answer: (B) The products of ecosystem processes
Example given by NCERT: the purification of air and water by forests.
Q78 of 106
NEET NCERT Line-by-Line
Which statement about energy and nutrients is CORRECT?
(A)
Both energy and nutrients cycle
(B)
Both energy and nutrients flow unidirectionally
(C)
Energy flows unidirectionally; nutrients cycle
(D)
Nutrients flow unidirectionally; energy cycles
Show Answer & NCERT Explanation
Correct Answer: (C) Energy flows unidirectionally; nutrients cycle
Energy FLOWS (and is lost as heat). Nutrients CYCLE (and are reused). This is the single most examined idea in the chapter.
Q79 of 106
NEET NCERT Line-by-Line
Plants are called producers because they:
(A)
Decompose detritus
(B)
Store phosphorus
(C)
Eat other organisms
(D)
Fix carbon dioxide
Show Answer & NCERT Explanation
Correct Answer: (D) Fix carbon dioxide
NCERT Exercise 1(a): plants are producers (autotrophs) because they fix CO₂.
Q80 of 106
NEET NCERT Line-by-Line
Which has the LARGEST population in a food chain?
(A)
Producers
(B)
Primary consumers
(C)
Secondary consumers
(D)
Decomposers
Show Answer & NCERT Explanation
Correct Answer: (A) Producers
Producers — they form the broad base of the pyramid of numbers. (NCERT Exercise Q2.)
Q81 of 106
NEET NCERT Line-by-Line
The SECOND trophic level in a lake is:
(A)
Phytoplankton
(B)
Zooplankton
(C)
Benthos
(D)
Fishes
Show Answer & NCERT Explanation
Correct Answer: (B) Zooplankton
Zooplankton. Phytoplankton are the FIRST trophic level (producers) — this is the trap.
Q82 of 106
NEET NCERT Line-by-Line
Common detritivores in our ecosystem are:
(A)
Phytoplankton
(B)
Fungi
(C)
Earthworms
(D)
Bacteria
Show Answer & NCERT Explanation
Correct Answer: (C) Earthworms
Earthworms — they carry out FRAGMENTATION, the first step of decomposition. (NCERT Exercise 1d.)
Q83 of 106
NEET NCERT Line-by-Line
The death of an organism marks the beginning of:
(A)
Photosynthesis
(B)
Nutrient uptake
(C)
The grazing food chain
(D)
The detritus food chain/web
Show Answer & NCERT Explanation
Correct Answer: (D) The detritus food chain/web
Dead organisms become detritus — the starting point of the DFC.
Q84 of 106
NEET NCERT Line-by-Line
Which statement about the amount of energy at successive trophic levels is TRUE?
(A)
It decreases
(B)
It fluctuates randomly
(C)
It increases
(D)
It stays the same
Show Answer & NCERT Explanation
Correct Answer: (A) It decreases
It decreases — 10% law. Organisms at each level depend on the level below for their energy.
Q85 of 106
NEET NCERT Line-by-Line
In most ecosystems, the pyramids of number, biomass and energy are:
(A)
All inverted
(B)
All upright
(C)
Number inverted, others upright
(D)
Energy inverted, others upright
Show Answer & NCERT Explanation
Correct Answer: (B) All upright
In most ecosystems all three are upright. The two exceptions are the tree (numbers) and the sea (biomass).
Q86 of 106
NEET NCERT Line-by-Line
Any calculation of energy, biomass or numbers in an ecological pyramid must:
(A)
Use fresh weight only
(B)
Sample only the dominant species
(C)
Include ALL organisms at that trophic level
(D)
Exclude decomposers and juveniles
Show Answer & NCERT Explanation
Correct Answer: (C) Include ALL organisms at that trophic level
NCERT: 'No generalisations we make will be true if we take only a few individuals at any trophic level into account.'
Q87 of 106
NEET NCERT Line-by-Line
Which is the correct relationship?
(A)
Litter and detritus are identical
(B)
Detritus contains no faecal matter
(C)
Litter is broader than detritus
(D)
Detritus is broader than litter
Show Answer & NCERT Explanation
Correct Answer: (D) Detritus is broader than litter
Detritus is broader — it includes dead plant remains, dead animal remains AND faecal matter. Litter (dead plant material on the soil surface) is one part of it.
Q88 of 106
NEET NCERT Line-by-Line
Production and decomposition differ in that:
(A)
Production builds complex organic matter from inorganic; decomposition breaks it back down
(B)
Both build organic matter
(C)
Both require sunlight
(D)
Production breaks down organic matter; decomposition builds it
Show Answer & NCERT Explanation
Correct Answer: (A) Production builds complex organic matter from inorganic; decomposition breaks it back down
Production = photosynthesis (needs sunlight). Decomposition = breakdown (needs oxygen).
Q89 of 106
NEET NCERT Line-by-Line
Which of the following correctly describes energy flow?
(A)
Cyclic, from consumers back to producers
(B)
Unidirectional, from the sun to producers to consumers
(C)
Bidirectional between all trophic levels
(D)
Random
Show Answer & NCERT Explanation
Correct Answer: (B) Unidirectional, from the sun to producers to consumers
Unidirectional. All organisms depend on producers directly or indirectly, and energy is lost as heat at each step.
Q90 of 106
NEET NCERT Line-by-Line
The pyramid of biomass in most terrestrial ecosystems shows:
(A)
An inverted shape
(B)
A sharp INCREASE in biomass at higher trophic levels
(C)
A sharp DECREASE in biomass at higher trophic levels
(D)
Equal biomass at all levels
Show Answer & NCERT Explanation
Correct Answer: (C) A sharp DECREASE in biomass at higher trophic levels
NCERT Figure 12.4(b): a sharp decrease in biomass at higher trophic levels.
Q91 of 106
NEET NCERT Line-by-Line
Which of the following pairs is CORRECTLY matched?
(A)
Leaching — release of available nutrients
(B)
Catabolism — earthworm
(C)
Fragmentation — bacterial enzymes
(D)
Humification — accumulation of humus in soil
Show Answer & NCERT Explanation
Correct Answer: (D) Humification — accumulation of humus in soil
Fragmentation → detritivores (earthworm). Catabolism → bacterial/fungal enzymes. Leaching → nutrients become UNAVAILABLE salts. Humification → humus accumulates in the soil. ✔
Q92 of 106
NEET NCERT Line-by-Line
An ecosystem's INPUT, TRANSFER and OUTPUT correspond respectively to:
(A)
Productivity; food web + nutrient cycling; degradation and energy loss
(B)
Decomposition; productivity; energy flow
(C)
Energy loss; nutrient cycling; productivity
(D)
Stratification; species composition; productivity
Show Answer & NCERT Explanation
Correct Answer: (A) Productivity; food web + nutrient cycling; degradation and energy loss
This is exactly how NCERT frames the chapter's structure.
Q93 of 106
NEET NCERT Line-by-Line
Which statement about the number of trophic levels in a DETRITUS food chain is most accurate?
(A)
It is restricted by the same 10% law as the GFC
(B)
It is not restricted in the same way, because detritus arrives from every level of the GFC
(C)
It always has exactly three levels
(D)
It has no trophic levels
Show Answer & NCERT Explanation
Correct Answer: (B) It is not restricted in the same way, because detritus arrives from every level of the GFC
The DFC's energy base is continually replenished by dead matter from the entire system, not by a single lower step.
Q94 of 106
NEET NCERT Line-by-Line
Zooplankton in a pond are:
(A)
Abiotic components
(B)
Producers
(C)
Consumers
(D)
Decomposers
Show Answer & NCERT Explanation
Correct Answer: (C) Consumers
Consumers, along with the free-swimming and bottom-dwelling forms.
Q95 of 106
NEET NCERT Line-by-Line
Which of these is NOT a product of decomposition?
(A)
Carbon dioxide
(B)
Water
(C)
Inorganic nutrients
(D)
Glucose
Show Answer & NCERT Explanation
Correct Answer: (D) Glucose
Decomposition yields CO₂, water and inorganic nutrients (plus humus). Glucose is a product of production (photosynthesis).
Q96 of 106
NEET NCERT Line-by-Line
Which statement about GPP is TRUE?
(A)
A considerable amount of GPP is utilised by plants in respiration
(B)
GPP is the biomass available to herbivores
(C)
GPP is the rate of formation of organic matter by consumers
(D)
GPP is always equal to NPP
Show Answer & NCERT Explanation
Correct Answer: (A) A considerable amount of GPP is utilised by plants in respiration
That respiration cost is exactly why NPP = GPP − R, and it is NPP (not GPP) that heterotrophs get.
Q97 of 106
NEET NCERT Line-by-Line
A pyramid of numbers with a very narrow base and progressively wider levels above suggests:
(A)
A grassland ecosystem
(B)
A tree ecosystem
(C)
The open sea
(D)
A desert
Show Answer & NCERT Explanation
Correct Answer: (B) A tree ecosystem
One tree (narrow base) → many insects → fewer birds. This is the inverted pyramid of numbers in a tree ecosystem.
Q98 of 106
NEET NCERT Line-by-Line
Which of the following statements is FALSE?
(A)
Nutrients are used repeatedly in an ecosystem
(B)
Energy is lost as heat at each trophic transfer
(C)
Energy can be recycled within an ecosystem
(D)
The sun is the only energy source for almost all ecosystems
Show Answer & NCERT Explanation
Correct Answer: (C) Energy can be recycled within an ecosystem
Energy can NEVER be recycled. It flows unidirectionally and is dissipated as heat.
Q99 of 106
NEET NCERT Line-by-Line
The rich soil deposit at the bottom of a pond is classified as:
(A)
An autotrophic component
(B)
A consumer
(C)
A decomposer
(D)
An abiotic component
Show Answer & NCERT Explanation
Correct Answer: (D) An abiotic component
It is part of the pond's abiotic component, along with the water and its dissolved substances.
Q100 of 106
NEET NCERT Line-by-Line
Which is TRUE of the pyramid of energy in a food chain?
(A)
It is always upright
(B)
It excludes producers
(C)
It is measured in numbers of individuals
(D)
It may be inverted in aquatic ecosystems
Show Answer & NCERT Explanation
Correct Answer: (A) It is always upright
Always upright, never inverted — heat loss at every step guarantees it.
Q101 of 106
NEET NCERT Line-by-Line
The rate of assimilation of food energy by consumers is called:
(A)
Net primary productivity
(B)
Secondary productivity
(C)
Standing crop
(D)
Gross primary productivity
Show Answer & NCERT Explanation
Correct Answer: (B) Secondary productivity
Secondary productivity — the rate of formation of new organic matter by consumers.
Q102 of 106
NEET NCERT Line-by-Line
In the pond ecosystem, the sequence of events that repeats over and over is:
(A)
Release → conversion → decomposition → consumption
(B)
Consumption → decomposition → conversion → release
(C)
Conversion of inorganic to organic → consumption by heterotrophs → decomposition and mineralisation → release for reuse
(D)
Decomposition → consumption → conversion → storage
Show Answer & NCERT Explanation
Correct Answer: (C) Conversion of inorganic to organic → consumption by heterotrophs → decomposition and mineralisation → release for reuse
Autotrophs fix energy → heterotrophs consume → decomposers mineralise → nutrients released for reuse → repeat.
Q103 of 106
NEET NCERT Line-by-Line
Which of the following would you find at the APEX of an ecological pyramid?
(A)
Decomposers
(B)
Producers
(C)
Herbivores
(D)
The tertiary or top-level consumer
Show Answer & NCERT Explanation
Correct Answer: (D) The tertiary or top-level consumer
Base = producers; apex = tertiary/top-level consumer.
Q104 of 106
NEET NCERT Line-by-Line
NPP of the whole biosphere is ~170 billion tons and ocean NPP is 55 billion tons. Land NPP is therefore approximately:
(A)
55 billion tons
(B)
115 billion tons
(C)
170 billion tons
(D)
225 billion tons
Show Answer & NCERT Explanation
Correct Answer: (B) 115 billion tons
170 − 55 = 115 billion tons.
Q105 of 106
NEET NCERT Line-by-Line
Which of the following is a correct statement about consumers?
(A)
They are heterotrophs and depend on plants directly or indirectly
(B)
They fix carbon dioxide
(C)
They form the first trophic level
(D)
They are autotrophs
Show Answer & NCERT Explanation
Correct Answer: (A) They are heterotrophs and depend on plants directly or indirectly
Consumers = heterotrophs. All animals depend on plants directly or indirectly for food.
Q106 of 106
NEET NCERT Line-by-Line
Which term describes the interconnection of many food chains in a natural ecosystem?
(A)
Food chain
(B)
Food web
(C)
Trophic level
(D)
Standing crop
Show Answer & NCERT Explanation
Correct Answer: (B) Food web
A food web — created because omnivores and shared prey link chains together.