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NEET Ecosystem: 5 practice MCQs with answers

By the PrepMatic team · Updated 9 Oct 2026 · 3 min read

Ecosystem is a Class 12 Biology chapter on how energy flows and nutrients cycle through living communities, and it is one of the easier chapters to score in. The five MCQs below test net primary productivity, the 10 per cent law, ecological pyramids, the last step of decomposition and pioneer species in succession.

What this chapter covers in the NEET syllabus

The NMC unit is Ecology and Environment, and this page covers the NCERT Class 12 chapter Ecosystem. The topics are:

• Ecosystem structure and function: components, patterns and the idea of stratification.
• Productivity: gross and net primary productivity, secondary productivity.
• Decomposition: detritus, fragmentation, leaching, catabolism, humification and mineralisation.
• Energy flow: food chains (grazing and detritus), food webs, trophic levels and the 10 per cent law.
• Ecological pyramids of number, biomass and energy.
• Ecological succession, nutrient cycling (carbon and phosphorus) and ecosystem services.

Five practice MCQs on the Ecosystem

Question 1

In an ecosystem the gross primary productivity (GPP) is 100 units and the energy lost in plant respiration is 40 units. The net primary productivity (NPP) is:

• A. 60 units
• B. 140 units
• C. 40 units
• D. 100 units

Question 2

Producers in a grassland trap 10,000 kJ of energy. If 10 per cent is transferred at each trophic level, the energy available to the secondary consumers is:

• A. 1000 kJ
• B. 10 kJ
• C. 100 kJ
• D. 10,000 kJ

Question 3

Which of the following ecological pyramids is always upright?

• A. Pyramid of numbers
• B. Pyramid of energy
• C. Pyramid of biomass
• D. All the pyramids

Question 4

The process in which inorganic nutrients are released from humus is called:

• A. fragmentation
• B. leaching
• C. humification
• D. mineralisation

Question 5

The pioneer species in primary succession on a bare rock are typically:

• A. lichens
• B. mosses
• C. herbs
• D. shrubs

Answers and explanations

1. A. Net primary productivity = GPP − respiratory losses = 100 − 40 = 60 units. NPP is the biomass available to consumers. The same relation is the one NCERT states: GPP minus R equals NPP.
2. C. Producers are the first trophic level, primary consumers the second and secondary consumers the third. With 10% transferred at each step: 10,000 → 1000 kJ (primary consumers) → 100 kJ (secondary consumers). Option A is the energy at the primary consumer level.
3. B. The pyramid of energy is always upright, because energy flowing through trophic levels is lost as heat at each step, so a lower level always has more energy. Pyramids of numbers and biomass can be inverted, as in a tree with many insects or a pond with phytoplankton.
4. D. Humus is slowly decomposed by microbes and the inorganic nutrients are released in mineralisation. Fragmentation breaks detritus into smaller bits, leaching moves soluble nutrients down, and humification forms dark humus.
5. A. On bare rock, lichens are the pioneers: they release acids that weather the rock and help soil formation. Mosses, herbs and shrubs follow in the sequence of primary succession (a xerarch succession).

How to prepare the Ecosystem chapter

• Learn the energy flow numbers NCERT gives. The 10 per cent law (Lindeman), the standing crop concept, and the share of incident solar radiation that is photosynthetically active (PAR, less than 50 per cent), of which plants capture only 2 to 10 per cent. Practise short calculations on GPP, NPP and energy at each trophic level.
• Distinguish pyramids with examples. Which is inverted and why: pyramid of numbers (a tree ecosystem), biomass (a sea ecosystem), and energy (never inverted). The shape is a favourite question.
• Memorise decomposition steps in order: fragmentation, leaching, catabolism, humification and mineralisation. Know the factors that affect the rate: temperature, moisture, oxygen and the chemical nature of detritus (lignin and chitin slow it, nitrogen and sugars speed it).
• Understand succession with a flow chart. Pioneer species, seral stages, and climax community for both xerarch (rock) and hydrarch (water) succession. Compare primary and secondary succession.
• Compare the carbon and phosphorus cycles, including the reservoir, the role of the atmosphere, and human influence.

An hour of diagrams (food web, pyramids, cycles, succession) followed by two short revisions covers the chapter. The NEET Biology preparation guide shows how to fit it into your plan, and the NEET syllabus lists every unit.

Take a full Ecosystem test on PrepMatic

Ecosystem is a chapter where a test can lift your confidence quickly. A PrepMatic topic test (about 15 questions in 30 minutes) shows your score with NEET's negative marking, and the free Basic plan includes topic tests. The rest of the NEET chapter practice is on the practice hub.

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