Ecosystem NEET MCQs practice quiz with assertion reason and match the following questions

Ecosystem NEET MCQs: 25 MCQs, Assertion Reason, Match the Following

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Ecosystem NEET MCQs are one of the most scoring parts of NEET Biology, because almost every question comes straight from NCERT Class 12 Chapter 12. Practising Ecosystem NEET MCQs on trophic levels, productivity, decomposition, energy flow and ecological pyramids helps you spot the patterns NTA repeats every year. Use these Ecosystem NEET MCQs after reading the chapter: answer each question yourself first, then tap Show Answer to check your reasoning. If you get a question wrong, revise that topic and come back to these Ecosystem NEET MCQs again before your mock test.

Ecosystem NEET MCQs: ecological pyramids of energy, number and biomass from NCERT Class 12
Ecological pyramids, a favourite topic in Ecosystem NEET MCQs.

These Ecosystem NEET MCQs cover the whole NCERT chapter: 25 multiple-choice questions, 10 assertion–reason questions and 6 match-the-following sets, each with an answer and a short explanation.

NCERT Class 12 Biology, Chapter 12 (Ecosystem), 2026-27 syllabus. Read each question and its four options, then tap Show Answer to check. Need the theory first? Read the Ecosystem NEET notes.

Ecosystem NEET MCQs with answers

Q1. The second trophic level in a lake is

  1. (a) Phytoplankton
  2. (b) Zooplankton
  3. (c) Benthos
  4. (d) Fishes
Show Answer

Answer: (b) Zooplankton

Zooplankton feed on phytoplankton (NCERT Exercise Q3).

Q2. Which of the following is an abiotic component of a pond?

  1. (a) Phytoplankton
  2. (b) Zooplankton
  3. (c) Dissolved oxygen
  4. (d) Fungi
Show Answer

Answer: (c) Dissolved oxygen

Dissolved oxygen is a non-living factor.

Q3. Vertical distribution of different species occupying different levels is called

  1. (a) Zonation
  2. (b) Stratification
  3. (c) Succession
  4. (d) Stagnation
Show Answer

Answer: (b) Stratification

NCERT calls vertical layering stratification (trees, shrubs, herbs, grasses).

Q4. Primary productivity is expressed as

  1. (a) g m⁻²
  2. (b) kcal m⁻²
  3. (c) g m⁻² yr⁻¹
  4. (d) kcal
Show Answer

Answer: (c) g m⁻² yr⁻¹

Productivity is a rate, so it has a time unit.

Q5. Net primary productivity equals

  1. (a) GPP + R
  2. (b) GPP − R
  3. (c) R − GPP
  4. (d) GPP × R
Show Answer

Answer: (b) GPP − R

NPP is what remains after respiration losses.

Q6. Annual net primary productivity of the whole biosphere is about

  1. (a) 55 billion tons
  2. (b) 115 billion tons
  3. (c) 170 billion tons
  4. (d) 1700 billion tons
Show Answer

Answer: (c) 170 billion tons

NCERT: about 170 billion tons (dry weight) of organic matter.

Q7. Productivity of oceans is about

  1. (a) 55 billion tons
  2. (b) 170 billion tons
  3. (c) 115 billion tons
  4. (d) 10 billion tons
Show Answer

Answer: (a) 55 billion tons

Despite covering ~70% of the surface, oceans produce only ~55 billion tons.

Q8. Secondary productivity is the rate of

  1. (a) Photosynthesis by producers
  2. (b) Formation of new organic matter by consumers
  3. (c) Respiration by plants
  4. (d) Decomposition
Show Answer

Answer: (b) Formation of new organic matter by consumers

Defined by NCERT as the rate of formation of new organic matter by consumers.

Q9. The raw material for decomposition is

  1. (a) Humus
  2. (b) Detritus
  3. (c) Minerals
  4. (d) Standing crop
Show Answer

Answer: (b) Detritus

Dead plant and animal remains (detritus).

Q10. Breakdown of detritus into smaller particles by earthworms is

  1. (a) Catabolism
  2. (b) Leaching
  3. (c) Fragmentation
  4. (d) Mineralisation
Show Answer

Answer: (c) Fragmentation

Detritivores carry out fragmentation.

Q11. Water-soluble inorganic nutrients going down into the soil and precipitating as unavailable salts is

  1. (a) Leaching
  2. (b) Humification
  3. (c) Catabolism
  4. (d) Fragmentation
Show Answer

Answer: (a) Leaching

This is leaching.

Q12. Humus is

  1. (a) Highly resistant to microbial action and decomposes slowly
  2. (b) Rapidly decomposed
  3. (c) Rich in lignin only
  4. (d) Part of the abiotic standing crop
Show Answer

Answer: (a) Highly resistant to microbial action and decomposes slowly

Humus is dark, amorphous, colloidal and resistant to microbes.

Q13. Decomposition is slowest when detritus is rich in

  1. (a) Sugars
  2. (b) Nitrogen
  3. (c) Lignin and chitin
  4. (d) Water-soluble substances
Show Answer

Answer: (c) Lignin and chitin

Lignin and chitin decompose slowly.

Q14. Decomposition is favoured by

  1. (a) Cold and dry conditions
  2. (b) Warm and moist conditions
  3. (c) Anaerobic conditions
  4. (d) Low temperature
Show Answer

Answer: (b) Warm and moist conditions

Warm, moist, aerobic conditions speed decomposition.

Q15. Of the incident solar radiation, PAR is

  1. (a) 100%
  2. (b) less than 50%
  3. (c) about 90%
  4. (d) 2–10%
Show Answer

Answer: (b) less than 50%

Less than 50% of incident radiation is PAR.

Q16. Plants capture what percentage of PAR?

  1. (a) 2–10%
  2. (b) 50%
  3. (c) 20–30%
  4. (d) 0.1%
Show Answer

Answer: (a) 2–10%

Only 2–10% of PAR is captured.

Q17. Except for one ecosystem, the sun is the only source of energy. That exception is

  1. (a) Desert
  2. (b) Deep-sea hydrothermal ecosystem
  3. (c) Tundra
  4. (d) Estuary
Show Answer

Answer: (b) Deep-sea hydrothermal ecosystem

Hydrothermal vents run on chemosynthesis.

Q18. Energy flow in an ecosystem is

  1. (a) Bidirectional
  2. (b) Cyclic
  3. (c) Unidirectional
  4. (d) Multidirectional
Show Answer

Answer: (c) Unidirectional

Energy moves one way from sun to producers to consumers.

Q19. Secondary producers are

  1. (a) Herbivores
  2. (b) Producers
  3. (c) Carnivores
  4. (d) None of the above
Show Answer

Answer: (a) Herbivores

NCERT Exercise Q4: herbivores form new organic matter (secondary productivity).

Q20. If producers fix 20,000 J, energy available to secondary consumers is

  1. (a) 2000 J
  2. (b) 200 J
  3. (c) 20 J
  4. (d) 2 J
Show Answer

Answer: (b) 200 J

20,000 → 2000 (herbivore) → 200 (carnivore).

Q21. In a terrestrial ecosystem, a much larger fraction of energy flows through

  1. (a) Grazing food chain
  2. (b) Detritus food chain
  3. (c) Parasitic chain
  4. (d) None
Show Answer

Answer: (b) Detritus food chain

NCERT states this for terrestrial ecosystems.

Q22. Decomposers are

  1. (a) Autotrophs
  2. (b) Heterotrophic saprotrophs, mainly fungi and bacteria
  3. (c) Chemoautotrophs only
  4. (d) Primary consumers
Show Answer

Answer: (b) Heterotrophic saprotrophs, mainly fungi and bacteria

They are heterotrophs that digest dead matter.

Q23. The pyramid that is always upright is that of

  1. (a) Number
  2. (b) Biomass
  3. (c) Energy
  4. (d) Biomass in sea
Show Answer

Answer: (c) Energy

Energy decreases at every step.

Q24. In NCERT’s grassland pyramid of numbers, about 6 million plants support how many top carnivores?

  1. (a) 3
  2. (b) 30
  3. (c) 300
  4. (d) 3000
Show Answer

Answer: (a) 3

NCERT Figure 12.4(a): only three top carnivores.

Q25. Which is NOT a limitation of ecological pyramids?

  1. (a) Saprophytes are not given a place
  2. (b) Food webs are ignored
  3. (c) A species may belong to two trophic levels
  4. (d) Producers are placed at the base
Show Answer

Answer: (d) Producers are placed at the base

Placing producers at the base is a rule, not a limitation.

Ecosystem NEET assertion–reason questions

(a) Both A and R true, R explains A. (b) Both true, R does not explain A. (c) A true, R false. (d) A false, R true.

AR1. Assertion (A): Pyramid of energy is always upright.
Reason (R): At each trophic level some energy is lost as heat.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

Heat loss means each higher level has less energy.

AR2. Assertion (A): Primary productivity varies between ecosystems.
Reason (R): It depends on plant species, environmental factors, nutrient availability and photosynthetic capacity of plants.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

These are the factors listed by NCERT.

AR3. Assertion (A): NPP is always less than GPP.
Reason (R): Plants use part of GPP in respiration.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

NPP = GPP − R and R > 0.

AR4. Assertion (A): In aquatic ecosystems, GFC is the major conduit of energy flow.
Reason (R): Decomposers are absent in aquatic ecosystems.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (c) A is true but R is false.

Decomposers are present in all ecosystems; GFC dominates in water because most aquatic producers are eaten.

AR5. Assertion (A): Humus is a reservoir of nutrients.
Reason (R): Humus decomposes very rapidly.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (c) A is true but R is false.

Humus is resistant to microbes and decomposes very slowly.

AR6. Assertion (A): Decomposition is slow in cold regions.
Reason (R): Low temperature inhibits decomposer activity.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

Decomposition is inhibited at low temperature.

AR7. Assertion (A): Pyramid of number for an ecosystem dominated by trees is inverted.
Reason (R): One big tree supports many insects.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

Many insects feed on a single tree, so the base is narrow.

AR8. Assertion (A): Energy flow in an ecosystem is unidirectional.
Reason (R): Energy captured by producers does not revert to the sun.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

Energy is lost as heat and cannot return to the sun.

AR9. Assertion (A): Earthworms are detritivores.
Reason (R): They are chemosynthetic producers.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (c) A is true but R is false.

Earthworms are detritivores (heterotrophs), not producers.

AR10. Assertion (A): Pyramid of biomass in the sea is generally inverted.
Reason (R): The biomass of fishes far exceeds that of phytoplankton.

  1. (a) Both A and R are true and R is the correct explanation of A.
  2. (b) Both A and R are true but R is not the correct explanation of A.
  3. (c) A is true but R is false.
  4. (d) A is false but R is true.
Show Answer

Answer: (a) Both A and R are true and R is the correct explanation of A.

NCERT gives exactly this reason: a small standing crop of phytoplankton supports a much larger standing crop of consumers.

Ecosystem NEET match the following

Match 1

Column I Column II
A. Fragmentation i. Enzymatic degradation by bacteria and fungi
B. Leaching ii. Formation of dark colloidal substance
C. Catabolism iii. Breakdown by detritivores
D. Humification iv. Downward movement of soluble nutrients

Choose the correct match for Match 1:

  1. (a) A-iii, B-iv, C-i, D-ii
  2. (b) A-iv, B-i, C-ii, D-iii
  3. (c) A-ii, B-i, C-iv, D-iii
  4. (d) A-iv, B-iii, C-ii, D-i
Show Answer

Answer: (a) A-iii, B-iv, C-i, D-ii

Match 2

Column I Column II
A. GPP i. Living mass of a trophic level at a time
B. NPP ii. Rate of new organic matter by consumers
C. Secondary productivity iii. GPP − R
D. Standing crop iv. Total rate of organic matter produced in photosynthesis

Choose the correct match for Match 2:

  1. (a) A-iii, B-ii, C-i, D-iv
  2. (b) A-iv, B-iii, C-ii, D-i
  3. (c) A-i, B-ii, C-iii, D-iv
  4. (d) A-iii, B-iv, C-i, D-ii
Show Answer

Answer: (b) A-iv, B-iii, C-ii, D-i

Match 3

Column I Column II
A. Pyramid of energy i. Inverted, phytoplankton base
B. Pyramid of biomass (sea) ii. Always upright
C. Pyramid of number (tree) iii. Upright
D. Pyramid of number (grassland) iv. Inverted, single producer

Choose the correct match for Match 3:

  1. (a) A-i, B-iv, C-iii, D-ii
  2. (b) A-iii, B-iv, C-i, D-ii
  3. (c) A-ii, B-i, C-iv, D-iii
  4. (d) A-i, B-ii, C-iii, D-iv
Show Answer

Answer: (c) A-ii, B-i, C-iv, D-iii

Match 4

Column I Column II
A. Producer i. Frog
B. Primary consumer ii. Fungi
C. Secondary consumer iii. Phytoplankton
D. Decomposer iv. Grasshopper

Choose the correct match for Match 4:

  1. (a) A-iv, B-i, C-ii, D-iii
  2. (b) A-ii, B-i, C-iv, D-iii
  3. (c) A-iv, B-iii, C-ii, D-i
  4. (d) A-iii, B-iv, C-i, D-ii
Show Answer

Answer: (d) A-iii, B-iv, C-i, D-ii

Match 5

Column I Column II
A. NPP of biosphere i. 2–10%
B. NPP of oceans ii. 55 billion tons
C. PAR in incident radiation iii. 170 billion tons
D. PAR captured by plants iv. less than 50%

Choose the correct match for Match 5:

  1. (a) A-iii, B-ii, C-iv, D-i
  2. (b) A-ii, B-iv, C-i, D-iii
  3. (c) A-i, B-iv, C-ii, D-iii
  4. (d) A-ii, B-iii, C-i, D-iv
Show Answer

Answer: (a) A-iii, B-ii, C-iv, D-i

Match 6

Column I Column II
A. Grazing food chain i. Interconnected food chains
B. Detritus food chain ii. Position of organism in food chain
C. Food web iii. Begins with dead organic matter
D. Trophic level iv. Begins with producers

Choose the correct match for Match 6:

  1. (a) A-iii, B-i, C-ii, D-iv
  2. (b) A-iv, B-iii, C-i, D-ii
  3. (c) A-ii, B-i, C-iii, D-iv
  4. (d) A-iii, B-iv, C-ii, D-i
Show Answer

Answer: (b) A-iv, B-iii, C-i, D-ii

Revise before more Ecosystem NEET MCQs

Practise these Ecosystem NEET MCQs again after revising the chapter. Check the official NCERT Biology Class 12 textbook and the NTA NEET website for the current syllabus.

Got some wrong? Revise productivity, decomposition, energy flow and pyramids with diagrams in Ecosystem NEET notes (NCERT Class 12, Chapter 12).

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