Environmental Issues

Syllabus Unit: Ecology and Environment

Why it matters

Chapter overview

Human activity has altered the atmosphere, water, soil and climate at a planetary scale, and NEET tests these environmental issues with the same precision as any physiology topic — exact pollutants, mechanisms and named international protocols. This topic covers air/water/soil pollution and their specific control measures, the greenhouse-driven mechanism of global warming and climate change, the distinct chemistry of ozone depletion and acid rain, and the practical waste-management and green practices used to reduce environmental damage.

Biology Syllabus Ecology and Environment 12%–14% weightage

Live Animation1 / 4

1Nutrient RunoffFertiliser/sewage enters water

2Algal BloomExplosive algae growth

3Oxygen DepletionDecomposers consume O2

4Aquatic Life DiesFish kills from hypoxia

1Air, Water & Soil Pollution

Pollution is contamination of the physical environment by substances or energy at levels harmful to living organisms — measurable, sourced, and controllable.

Learning Objectives

Define pollutant and distinguish point-source from non-point-source pollution.
Explain BOD (Biochemical Oxygen Demand) as an indicator of organic water pollution.
Describe eutrophication and its cause, process, and consequence for aquatic ecosystems.
State one major cause and one control measure each for air, water and soil pollution.

Key Terms

PollutantAny physical, chemical or biological substance released into the environment, unintentionally or deliberately, that has a harmful effect on living organisms.

Biochemical Oxygen Demand (BOD)The amount of dissolved oxygen consumed by microorganisms decomposing organic matter in a water sample; a direct measure of organic pollution load.

EutrophicationNutrient (nitrate/phosphate) enrichment of a water body from agricultural runoff or sewage, causing algal blooms that deplete dissolved oxygen and kill aquatic life.

Particulate Matter (PM)Fine solid or liquid particles suspended in air (e.g. PM2.5, PM10) from vehicle exhaust and industrial emissions, a major cause of respiratory disease.

**Pollution** is the addition of any substance or form of energy to the environment at a rate faster than it can be safely absorbed, dispersed or degraded, causing harm to living organisms.

Water pollution

**BOD (Biochemical Oxygen Demand)** measures the dissolved oxygen consumed by microbes decomposing organic waste in water over 5 days — a high BOD directly indicates heavy organic pollution (e.g. from sewage). Nutrient-rich runoff (nitrates, phosphates from fertilisers and sewage) causes **eutrophication**: explosive algal growth (algal bloom) blocks sunlight, and its subsequent decomposition depletes dissolved oxygen, causing mass fish kills.

Air pollution

Major air pollutants include **particulate matter (PM2.5, PM10)**, sulphur dioxide, nitrogen oxides and carbon monoxide, mostly from vehicle exhaust and industrial combustion. Catalytic converters in vehicles reduce CO and unburnt hydrocarbon emissions; electrostatic precipitators remove particulate matter from industrial flue gas before release.

Soil pollution

Excessive use of chemical pesticides and fertilisers, along with improper solid waste disposal, degrades soil quality and can contaminate groundwater — integrated pest management and controlled fertiliser use are the primary control measures.

Exam TipNEET frequently pairs pollutant with control device: catalytic converter → vehicle exhaust CO/hydrocarbons; electrostatic precipitator → industrial particulate matter.