Environmental pollution is a high-frequency NEET topic. Questions test whether you can distinguish pollutant types, name the correct control device or legislation, and match diseases to their causative pollutant. The common trap is term-swapping — confusing the specific pollutant source, the control method, or the regulatory body.
Air pollution. Major pollutants: particulate matter, SO₂, CO, NOₓ, hydrocarbons. Electrostatic precipitators (ESP) remove 99% of particulate matter from industrial exhaust (NCERT Class 12 Biology Chapter 16, page 302). Catalytic converters fitted to automobiles reduce CO, NOₓ, and unburnt hydrocarbons — the catalyst is typically platinum-palladium-rhodium. The key distinction: ESP is for particulate matter from industrial sources; catalytic converters are for gaseous emissions from vehicles.
Water pollution. Biological Oxygen Demand (BOD) measures organic pollution — high BOD means heavily polluted water because decomposing microorganisms consume dissolved oxygen. Eutrophication results from excess nutrients (phosphates, nitrates) causing algal blooms, oxygen depletion, and aquatic death. Biomagnification: concentration of non-biodegradable toxicants (DDT, mercury) increases at successive trophic levels — top predators carry the highest load.
Noise pollution. Sound above 150 dB damages eardrums. Chronic exposure above 80–85 dB causes hearing impairment. NEET questions test the threshold values and health effects.
Solid waste and e-waste. Remediation strategies: sanitary landfills, incineration, composting. E-waste (discarded electronic goods) contains toxic metals — lead, mercury, cadmium. Recycling in developing countries often occurs without safety measures, causing occupational health hazards.
Radioactive waste. Low-level waste is diluted and disposed; high-level waste is stored in shielded containers underground. UV-B radiation (linked to ozone depletion) causes skin cancer, cataracts, and immune suppression — a frequent cross-topic connection tested in NEET.
Watch-out: NEET stems often present a pollutant-control device and ask what it removes. Know the device–pollutant pairing precisely: ESP → particulates; scrubber → gases (SO₂); catalytic converter → CO, NOₓ, hydrocarbons.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which device is used in industrial smokestacks to remove over 99% of particulate matter from exhaust?
Biological Oxygen Demand (BOD) is a measure of:
Which of the following is the correct set of metals that make up the catalyst in an automobile catalytic converter?
A lake near an agricultural area receives heavy runoff of phosphate-rich fertilisers. Which sequence of events correctly describes what follows?
DDT sprayed on crops is found at the highest concentration in fish-eating birds rather than in the water or in small fish. This phenomenon is called:
An electrostatic precipitator uses electrode wires maintained at several thousand volts to produce a corona that charges soot particles. The charged particles are then collected on:
A student claims that the pyramid of energy in an aquatic ecosystem is inverted because phytoplankton biomass is less than zooplankton biomass at any given time. What is the error in this reasoning?
Consider the following pollutants and control devices:
Given
An automobile exhaust releases carbon monoxide (CO), oxides of nitrogen (NOₓ), and unburnt hydrocarbons. A catalytic converter is fitted to the exhaust system.
Required
Explain the role of the catalytic converter: what reactions does it catalyse, and what are the products?
Concept
A catalytic converter uses expensive metal catalysts (platinum, palladium, rhodium) to convert harmful gaseous pollutants into less harmful products through simultaneous oxidation and reduction reactions.
Formula
No quantitative formula applies. The conversion involves two reaction types: - Oxidation: 2CO + O₂ → 2CO₂; unburnt hydrocarbons + O₂ → CO₂ + H₂O - Reduction: 2NOₓ → N₂ + O₂ (rhodium catalyses the dissociation)
Substitution
Not applicable (qualitative mechanism question).
Calculation
Not applicable. The key factual steps: 1. Exhaust gases pass over the Pt-Pd-Rh catalyst bed. 2. CO is oxidised to CO₂. 3. Unburnt hydrocarbons are oxidised to CO₂ and H₂O. 4. NOₓ is reduced to N₂ and O₂. 5. Motor vehicles fitted with catalytic converters must use unleaded petrol because lead inactivates the catalyst.
Final answer
The catalytic converter simultaneously oxidises CO and hydrocarbons to CO₂ and H₂O, and reduces NOₓ to N₂ and O₂. The essential additional fact for NEET: unleaded petrol is mandatory because lead poisons the catalyst.
Common trap
Students confuse the electrostatic precipitator (for industrial particulate matter) with the catalytic converter (for automobile gaseous emissions). The ESP uses high-voltage electrodes; the catalytic converter uses precious-metal catalysts. Know the device–pollutant–source triplet.
Similar NEET-style question
"A catalytic converter fitted to automobile exhaust reduces emission of which of the following pollutants? (a) Particulate matter only (b) SO₂ and particulates (c) CO, NOₓ, and unburnt hydrocarbons (d) Lead and mercury vapour." Answer: (c). ---
Air: SOx, NOx, CO, particulates. Water: BOD ↑, eutrophication, biomagnification (DDT, mercury). Soil: pesticides, heavy metals. Noise > 60 dB harmful. E-waste: hazardous chemicals; recycling required.
-- NCERT Class 12 Biology, Ch. 13, p. 302Approximately 10% of energy at one trophic level is transferred to the next; rest dissipated as heat.
| Symbol | Quantity | SI Unit |
|---|---|---|
| E_n | energy at level n | kcal/m² |
Population grows exponentially at small N; growth slows as N approaches K (carrying capacity); equilibrium at N = K.
| Symbol | Quantity | SI Unit |
|---|---|---|
| N | population size | - |
| r | intrinsic rate of increase | /time |
| K | carrying capacity | - |
Number of species S in area A increases as a power law. Z (slope) = 0.1-0.2 for small areas, 0.6-1.2 for continents.
| Symbol | Quantity | SI Unit |
|---|---|---|
| S | species number | - |
| A | area | - |
| Z | slope | - |
| C | intercept | - |
These are the exact patterns that cause wrong answers in NEET. Each trap includes when it triggers and how to avoid it.
Category: Similar Terms
Mutualism benefits BOTH; commensalism benefits one, neutral for the other; parasitism +,−; predation +,−.
Question presents organism-pair interaction and asks for type.
Tabulate effects on each partner: (+,+), (+,0), (+,−), (−,−), (0,−), (0,0).
Root cause: term confusion
K-selected: large body, few offspring with high parental investment, long-lived (whales, humans, elephants). r-selected: small body, many offspring, low investment, short-lived (insects, weeds).
Root cause: concept gap
Pyramid of ENERGY is ALWAYS upright (10% law guarantees decreasing energy at higher trophic levels). Pyramid of NUMBER and BIOMASS can be inverted (e.g. ocean: small algae < large zooplankton at one moment).
44 questions from NEET 2020, 2021, 2022, 2023, 2024, 2025. Answers verified against NTA official keys.
Which of the following is the unit of productivity of an Ecosystem?
Which one of the following equations represents the Verhulst-Pearl Logistic Growth of population?
Who is known as the father of Ecology in India?
Epiphytes that are growing on a mango branch is an example of which of the following?
List of endangered species was released by-
Which of the following statements is incorrect?
The thickness of ozone in a column of air in the atmosphere is measured in terms of :
Which one of the following statements cannot be connected to Predation?
The gaseous plant growth regulator is used in plants to :
Which one of the following will accelerate phosphorus cycle?
Which one of the following statements is correct?
Which of the following statements is not true?
Which of the following is a correct statement?
Amensalism can be represented as: Select the correct answer from the options given
Select the correct pair. 141. Which of the following statements is incorrect?
In the exponential growth equation N = N ert, e t o
• ≈UÊ∑¸˜§Á≈U∑§ ˇÊ òÊ ◊ Á„◊-• œÃÊ Á∑§‚ ∑§Ê⁄UáÊ „Ê ÃË „Ò? temperature
Recurring question shapes from past papers. Each pattern shows why wrong options look tempting.
population interaction type confusion
Six interaction types form a 2x2 effect matrix (+,+), (+,-), (+,0), (-,-), (-,0), (0,0). Students who have memorised the symbols cannot always assign real organism pairs correctly: barnacles on a whale body = commensalism (+,0) not mutualism (+,+); mycorrhizal fungi on plant roots = mutualism not parasitism. The most common error is selecting mutualism for commensalism examples because both organisms are 'associated'.
ecological pyramid inversion error
Students learn that 'ecological pyramids can be inverted' from the examples of the number pyramid (tree-insects-birds) and the ocean biomass pyramid. They over-apply this to energy pyramids. The 10% law guarantees that energy ALWAYS decreases at each trophic level -- no realistic scenario inverts the energy pyramid. Questions ask which pyramid type 'can be inverted'; students select energy because they generalise the inversion rule.
k r selection confusion
K-selected species (large body, few offspring, high parental investment, long-lived: whales, humans, elephants) are confused with r-selected (small body, many offspring, no parental care: insects, frogs, bacteria). Students who associate 'reproducing as humans do = normal' call humans r-selected, or who associate 'complex animal = cared-for offspring' call oysters K-selected.
speciation type confusion
Sympatric speciation occurs in the same geographic area without physical isolation (e.g., polyploidy); allopatric speciation requires a geographic barrier. Students who cannot recall the Greek roots (sym = same, allo = different) confuse the two when a question describes a real-world scenario and asks which speciation type it illustrates.
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