Section 11 — NEET-Pattern Practice Questions (Ecosystem)
Ecosystem is a compact, high-return NEET chapter — most of its questions come from a small set of recurring ideas, and they are usually gettable if your definitions and numbers are tight. The questions sweep across the whole chapter: the structure of an ecosystem (abiotic and biotic components, species composition, stratification), productivity (GPP, NPP and secondary productivity), decomposition and its steps, energy flow and the laws of thermodynamics, trophic levels and standing crop, grazing and detritus food chains, food webs, the ten per cent law, and the three ecological pyramids.
This section is a focused 28-question practice quiz covering the entire chapter — a mix of straight recall (definitions, units, examples), concept traps (production vs productivity, GFC vs DFC, upright vs inverted pyramids) and a few short numericals on GPP - R = NPP and the ten per cent law.
Important note: These are NEET-pattern practice questions built on the recurring core concepts of this chapter. Do not treat them as exact authenticated year-tagged NEET papers unless each one is separately matched against an official paper and year.
How to use: Treat this like a timed mock — give yourself about 30 minutes for all 28 questions (roughly a minute each). Attempt first, then read each explanation carefully. Skim the recap of recurring hooks below to spot the question patterns before you begin.
Recurring Hooks — What NEET Keeps Asking on This Chapter
Most questions on Ecosystem fall into these repeating patterns:
1. Productivity numbers and the GPP relation. Primary production is biomass per unit area (g m-2 or kcal m-2); productivity is a rate (g m-2 yr-1). The one relation to lock in is where R is respiration loss and NPP is the biomass available to heterotrophs. Biosphere NPP is about 170 billion tons (dry weight); oceans give only about 55 billion tons despite covering about 70 per cent of the surface.
2. The PAR figures. Less than 50 per cent of incident solar radiation is photosynthetically active radiation (PAR), and plants capture only 2-10 per cent of that PAR.
3. Decomposition steps. Fragmentation, leaching, catabolism, humification and mineralisation; fragmentation, leaching and catabolism operate simultaneously. Slower with lignin and chitin, quicker with nitrogen and sugars; favoured by warm, moist conditions.
4. Energy flow and the laws. Flow is unidirectional (first law); a constant energy input is needed to fight rising entropy (second law). Deep-sea hydrothermal vents are the one exception to the sun as the energy source.
5. Trophic levels and standing crop. Producers = first level, herbivores = second, carnivores = third; energy decreases at each level. Standing crop is measured as biomass (dry weight is more accurate) or number. A trophic level is a functional level, not a species.
6. The ten per cent law. Only about 10 per cent of energy passes to the next higher level, which is why food chains are short.
7. Pyramid rules. Base = producers, apex = top consumer. The pyramid of energy is always upright (energy lost as heat at each step). The pyramid of numbers can be inverted (many insects on one big tree) and the pyramid of biomass in the sea is generally inverted (fish biomass exceeds phytoplankton).