25 questions in 25 minutes on the NTA computer-based test interface, all from Ecosystem. +4 / -1 marking, instant score, full solutions. Free, no login.
A chapter test is the fastest honest check on whether a chapter has actually landed. This one draws 25 questions from Ecosystem, of which 19 are real NEET previous-year questions and 0 sit at the harder end of the bank. Sit it in one 25-minute block, the way you would in the hall.
Revising first? Read the Ecosystem chapter notes, then come back and take this test to check it stuck.
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Duration: 180 minutes · 180 questions · 720 marks maximum
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NEET CBT mock test: common questions
How many questions are in this Ecosystem mock test?
25 questions in 25 minutes, marked +4 for a correct answer and -1 for a wrong one, exactly like the real paper. 19 of them are NEET previous-year questions.
Is this the same interface as the real NEET CBT?
Yes. On-screen countdown, colour-coded question palette, Save & Next, Clear Response and Mark for Review, then an instant score with full solutions.
Should I take this before or after revising Ecosystem?
Both, and that is the point. Take it cold to find out what you actually do not know, revise from the chapter notes, then retake it to confirm the gap closed.
All 25 questions with answers and solutions
The complete paper in text form, with the correct option and a worked explanation for every question. Sit the timed test above first: the score is only worth having if you earn it. Then open this to revise, or to re-read a question you got wrong without replaying the whole paper.
Show all 25 questions with answers and solutions
Botany
- Q1In a terrestrial ecosystem such as a forest, the maximum energy is found in which trophic level?
- T₁
- T₃
- T₄
- T₂
Answer: (A) T₁
Energy decreases at each higher trophic level (~90% lost per transfer), so the maximum energy is always at the first trophic level (T₁), the producers, and the energy pyramid is upright.
- Q2Which of the following is expected to have the highest value (g m⁻² yr⁻¹) in a grassland ecosystem?
- Net production (NP)
- Secondary production (SP)
- Tertiary production (TP)
- Gross production (GP)
Answer: (D) Gross production (GP)
Gross primary production (GP) is the total energy/organic matter captured before any respiratory loss, so it is numerically the largest. Net production = GP − respiration is smaller, and secondary/tertiary production (by consumers) are smaller still due to the ~10% transfer.
- Q3The annual net primary productivity of the whole biosphere is approximately ____ billion tons of dry organic matter, of which oceans contribute about ____ billion tons.
- 55 ; 170
- 170 ; 100
- 170 ; 55
- 100 ; 170
Answer: (C) 170 ; 55
NCERT states the biosphere’s annual NPP is about 170 billion tons of dry organic matter, and despite covering ~70% of the surface, oceans contribute only about 55 billion tons.
- Q4Pick up the correct food chain:
- Grass → Fox → Rabbit → Bird
- Phytoplankton → Zooplankton → Fish
- Fallen leaves → Bacteria → Insect larvae
- Grass → Chameleon → Insect → Bird
Answer: (B) Phytoplankton → Zooplankton → Fish
A valid grazing food chain runs producer → primary consumer → secondary consumer: Phytoplankton (producer) → Zooplankton (herbivore) → Fish (carnivore). The others reverse the natural feeding order (e.g. fox cannot precede rabbit).
- Q5What is true of an ecosystem?
- Primary consumers are the least dependent upon producers
- Producers are more than primary consumers
- Secondary consumers are the largest and most powerful
- Primary consumers outnumber producers
Answer: (B) Producers are more than primary consumers
In any ecosystem the producers (green plants) form the base of the energy and number pyramid, so they are more numerous (and hold more energy) than the primary consumers (herbivores) that depend on them. Primary consumers are entirely dependent on producers, ruling out (A) and (B).
- Q6Presence of plants arranged into well-defined vertical layers depending on their height is best seen in a:
- temperate forest
- grassland
- tropical savannah
- tropical rain forest
Answer: (D) tropical rain forest
Stratification (vertical layering into strata/storeys) is most pronounced in a tropical rain forest, which has tall emergent trees, tall trees, smaller trees, a shrub layer and a ground layer of herbs and ferns. Grasslands lack such distinct vertical strata.
- Q7The primary producers of the deep-sea hydrothermal vent ecosystem are:
- green algae
- blue-green algae
- coral reefs
- chemosynthetic bacteria
Answer: (D) chemosynthetic bacteria
No sunlight reaches deep-sea hydrothermal vents, so photosynthesis is impossible. The primary producers are chemosynthetic (chemoautotrophic) bacteria/archaebacteria that oxidise inorganic compounds such as H2S for energy.
- Q8The transfer of energy from one trophic level to another is governed by the second law of thermodynamics. The average efficiency of energy transfer from herbivores to carnivores is about:
- 10%
- 5%
- 50%
- 25%
Answer: (A) 10%
By Lindeman’s 10% law, only about 10% of the energy at one trophic level is transferred to the next, so about 10% passes from herbivores to carnivores; the rest is lost as heat in respiration.
- Q9In a lake ecosystem, the second most important (second) trophic level is occupied by:
- zooplankton
- neuston
- phytoplankton
- benthos
Answer: (A) zooplankton
In a lake, phytoplankton are the producers (first trophic level). The zooplankton that feed on them are the primary consumers and so occupy the second trophic level.
- Q10The main role of bacteria in the carbon cycle involves:
- photosynthesis
- assimilation of nitrogenous compounds
- chemosynthesis
- digestion or breakdown of organic compounds
Answer: (D) digestion or breakdown of organic compounds
In the carbon cycle, decomposer bacteria (and fungi) digest/break down dead organic matter, releasing CO₂ back to the atmosphere. This decomposition is their main role; nitrogen assimilation belongs to the nitrogen cycle.
- Q11Primary succession refers to the development of communities on a:
- newly-exposed habitat with no record of earlier vegetation
- forest clearing after a devastating fire
- freshly cleared crop field
- pond freshly filled with water after a dry phase
Answer: (A) newly-exposed habitat with no record of earlier vegetation
Primary succession occurs in a totally barren area that has NO record of earlier vegetation (bare rock, new lava, fresh sand). The other options retain soil/organisms from a previous community, so they represent secondary succession.
- Q12Which set of climatic conditions favours the fastest rate of decomposition?
- Warm and moist environment
- Anaerobic and acidic environment
- Low temperature and anaerobiosis
- Cold and dry environment
Answer: (A) Warm and moist environment
Decomposition is largely an aerobic, oxygen-requiring process favoured by warmth and moisture. Low temperature and anaerobiosis inhibit decomposers and slow it down.
- Q13In a grass → deer → tiger food chain, if the grass biomass is one tonne, the tiger biomass shall be about:
- 1 kg
- 100 kg
- 200 kg
- 10 kg
Answer: (D) 10 kg
By the 10% law: grass = 1000 kg (T₁); deer = 10% = 100 kg (T₂); tiger = 10% of 100 = 10 kg (T₃). So the tiger biomass is about 10 kg.
- Q14A detritus food chain (DFC) begins with:
- Top carnivores
- Dead organic matter
- Green plants
- Herbivores
Answer: (B) Dead organic matter
The detritus food chain begins with dead organic matter (detritus), which is consumed by detritivores and decomposers. The grazing food chain instead begins with producers.
- Q15In the grazing food chain Grass → Grasshopper → Frog → Snake → Hawk, the frog occupies which trophic level?
- Second trophic level
- First trophic level
- Third trophic level
- Fourth trophic level
Answer: (C) Third trophic level
Grass = T1 (producer), grasshopper = T2 (primary consumer), frog = T3 (secondary consumer), snake = T4, hawk = T5. So the frog is at the third trophic level.
- Q16In a biotic community, the primary consumers are the:
- omnivores
- herbivores
- detritivores
- carnivores
Answer: (B) herbivores
Primary (first-order) consumers feed directly on producers, so they are the herbivores. Carnivores feed on other animals and occupy higher trophic levels.
- Q17What type of ecological pyramid would be obtained from the following data? Secondary consumer: 120 g; Primary consumer: 60 g; Primary producer: 10 g.
- Upright pyramid of numbers
- Upright pyramid of biomass
- Inverted pyramid of biomass
- Pyramid of energy
Answer: (C) Inverted pyramid of biomass
The data are in grams (biomass) and the value increases upward (producer 10 g < primary consumer 60 g < secondary consumer 120 g), i.e. the base is smaller than the apex. This gives an inverted pyramid of biomass.
- Q18If by radiation all nitrogenase enzymes are inactivated, then there will be no:
- conversion from ammonium to nitrate in soil
- conversion from nitrate to nitrite in legumes
- fixation of nitrogen in legumes
- fixation of atmospheric nitrogen
Answer: (D) fixation of atmospheric nitrogen
Nitrogenase catalyses the biological fixation of atmospheric N₂ into ammonia. If all nitrogenase is inactivated, ALL biological nitrogen fixation stops – not just in legumes but everywhere (free-living fixers too). So the broadest correct answer is no fixation of atmospheric nitrogen.
- Q19Which of the following pairs is a sedimentary type of biogeochemical cycle?
- Phosphorus and sulphur
- Oxygen and nitrogen
- Phosphorus and nitrogen
- Phosphorus and carbon dioxide
Answer: (A) Phosphorus and sulphur
Sedimentary cycles have their reservoir in the Earth’s crust (lithosphere). Both phosphorus and sulphur are sedimentary. Oxygen, nitrogen and carbon dioxide are gaseous cycles.
- Q20Which of the following is NOT one of the four functional attributes of an ecosystem described in NCERT?
- Productivity
- Stratification
- Energy flow
- Decomposition
Answer: (B) Stratification
The four functional aspects are productivity, decomposition, energy flow and nutrient cycling. Stratification is a STRUCTURAL feature (vertical layering of the community), not a function.
- Q21Decomposition would be slowest when the detritus is rich in:
- Lignin and chitin
- Nitrogen and sugars
- Simple carbohydrates
- Water-soluble substances
Answer: (A) Lignin and chitin
Detritus rich in lignin and chitin resists microbial attack and decomposes slowly, whereas detritus rich in nitrogen and water-soluble sugars decomposes rapidly.
- Q22A bamboo plant is growing in a forest. What will be its trophic level?
- Second trophic level (T₂)
- Fourth trophic level (T₄)
- Third trophic level (T₃)
- First trophic level (T₁)
Answer: (D) First trophic level (T₁)
Bamboo is a green plant (producer/autotroph), and producers always occupy the first trophic level (T₁) of a food chain.
- Q23In which of the following do both pairs have the correct combination of nutrient cycle type?
- Gaseous: carbon and nitrogen; Sedimentary: sulphur and phosphorus
- Gaseous: sulphur and phosphorus; Sedimentary: carbon and nitrogen
- Gaseous: carbon and sulphur; Sedimentary: nitrogen and phosphorus
- Gaseous: nitrogen and sulphur; Sedimentary: carbon and phosphorus
Answer: (A) Gaseous: carbon and nitrogen; Sedimentary: sulphur and phosphorus
Gaseous cycles have their reservoir in the atmosphere – carbon and nitrogen. Sedimentary cycles have their reservoir in the Earth’s crust/rocks – sulphur and phosphorus. So option (A) pairs both correctly.
- Q24Which one of the following ecosystems has the highest gross primary productivity?
- Coral reefs
- Mangroves
- Equatorial rain forest
- Grasslands
Answer: (A) Coral reefs
Among the options, coral reefs have the maximum gross primary productivity per unit area; they are among the most productive ecosystems on Earth (rivalled by estuaries). Deserts have the lowest.
- Q25The greatest biomass of autotrophs in the world’s oceans is that of:
- free-floating micro-algae, cyanobacteria and nanoplankton
- benthic brown algae and coastal red algae
- sea grasses and slime moulds
- benthic diatoms and marine viruses
Answer: (A) free-floating micro-algae, cyanobacteria and nanoplankton
The dominant producers of the open oceans are tiny free-floating phytoplankton – micro-algae (diatoms, dinoflagellates), cyanobacteria and nanoplankton – which together form the greatest autotroph biomass in the world’s oceans.