Paper IPaper I · General Science
Environment and Ecology
Ecosystems and food chains, energy flow and biogeochemical cycles, biodiversity and conservation, pollution types and pollutants, climate change and the ozone layer, international conventions and Indian environmental laws and bodies, with the security and disaster angle at CAPF recognition depth
CAPF wiki•10 min read•19 sections
At a glance
PaperPaper ISubjectGeneral ScienceSyllabusGeneral Science: general awareness, scientific temper, comprehension and appreciation of scientific phenomena of everyday observation, including new areas such as Information Technology, Biotechnology, and Environmental ScienceImportanceHigh
EnvironmentEcologyEcosystemFood ChainBiodiversityConservationPollutionClimate Change
Environmental Science is the third "new area" named in the CAPF syllabus, so it is a near-certain source of questions and overlaps with the current-affairs and geography slices of Paper I. This note covers ecosystems and energy flow, biodiversity and its conservation, the main pollution types and their pollutants, climate change and the ozone layer, and the headline international conventions and Indian environmental laws. CAPF tests the food-chain vocabulary, which gas causes which problem (CFCs and the ozone hole, carbon dioxide and warming), the convention-to-subject match (Montreal for ozone, Paris for climate, Ramsar for wetlands), and the year and subject of major Indian Acts. The convention and law tables below are exactly the matching material the exam favours.
- An ecosystem is a community of living organisms (biotic components) interacting with their non-living surroundings (abiotic components such as soil, water, air, sunlight).
- Producers (autotrophs): green plants that make food by photosynthesis, the base of every food chain.
- Consumers (heterotrophs): herbivores (primary), then carnivores (secondary and tertiary).
- Decomposers: bacteria and fungi that break down dead matter and recycle nutrients.
- A food chain shows energy passing from one trophic level to the next. By the ten percent law (Lindeman), only about 10 percent of the energy at one level passes to the next, so chains are short (usually three to five links).
- A food web is many interlinked food chains. An ecological pyramid shows the number, biomass or energy at each level; the energy pyramid is always upright.
- Biomagnification: non-biodegradable pollutants such as DDT and mercury build up at higher concentrations up the food chain.
- The carbon cycle, nitrogen cycle, water (hydrological) cycle and oxygen cycle recycle elements between organisms and the environment. Nitrogen-fixing bacteria (in legume root nodules) convert atmospheric nitrogen into a usable form.
- Biodiversity is the variety of life at three levels: genetic, species and ecosystem diversity.
- India is a megadiverse country with four biodiversity hotspots: the Himalaya, the Western Ghats and Sri Lanka, the Indo-Burma region, and Sundaland (which includes the Nicobar Islands).
- Conservation is in-situ (in the natural habitat: national parks, wildlife sanctuaries, biosphere reserves, tiger and elephant reserves) or ex-situ (away from habitat: zoos, gene banks, botanical gardens, seed banks).
- The IUCN Red List classifies species from Least Concern through Vulnerable, Endangered and Critically Endangered to Extinct in the Wild and Extinct.
- Flagship Indian programmes include Project Tiger (1973) and Project Elephant (1992).
- Biosphere reserves are large protected areas with a core, buffer and transition zone; some are recognised under the UNESCO Man and the Biosphere programme (for example the Nilgiri, the first in India).
- Ramsar sites are wetlands of international importance; India has a large and growing number (verify the latest count).
- National parks offer the strictest protection (no human activity), wildlife sanctuaries allow some regulated activity, and conservation and community reserves involve local participation.
- Tiger reserves are managed under the National Tiger Conservation Authority; Jim Corbett was India's first national park (1936).
- Renewable (non-conventional) energy sources do not run out and pollute less: solar, wind, hydro, biomass, geothermal and tidal.
- Non-renewable (conventional) sources are finite and polluting: coal, petroleum and natural gas (fossil fuels).
- India's institutions and targets include the Ministry of New and Renewable Energy, the International Solar Alliance (co-founded by India and France), and large national renewable-capacity goals (verify the latest targets).
- Sustainable development meets present needs without compromising future generations (the Brundtland definition); the UN Sustainable Development Goals (SDGs) run to 2030.
| Type |
Major pollutants or causes |
Headline effect |
| Air |
Carbon monoxide, sulphur dioxide, oxides of nitrogen, particulate matter (PM2.5, PM10) |
Smog, respiratory disease, acid rain |
| Water |
Sewage, industrial effluent, fertilisers, plastics |
Disease, eutrophication, dead zones |
| Soil |
Pesticides, plastics, heavy metals, e-waste |
Loss of fertility, food contamination |
| Noise |
Traffic, machinery, loudspeakers, construction |
Hearing loss, stress, sleep loss |
| Thermal |
Hot water from industry and power plants |
Lower dissolved oxygen, harm to aquatic life |
- Eutrophication is the over-enrichment of water with nutrients (nitrates, phosphates) that causes algal blooms and then oxygen depletion.
- Acid rain comes from sulphur dioxide and nitrogen oxides reacting with water vapour to form sulphuric and nitric acids.
- Smog is a mix of smoke and fog; photochemical smog forms from vehicle emissions in sunlight.
- The Air Quality Index (AQI) rates daily air quality from Good to Severe based on key pollutants.
- Greenhouse gases (carbon dioxide, methane, nitrous oxide, water vapour, CFCs) trap outgoing heat and warm the planet (the greenhouse effect); excess warming is global warming, leading to climate change, melting glaciers and rising seas.
- The ozone layer in the stratosphere absorbs harmful ultraviolet radiation. Chlorofluorocarbons (CFCs) deplete it, causing the ozone hole over Antarctica.
- Keep the distinction clear: CFCs cause ozone depletion, while carbon dioxide and methane drive global warming. Ground-level ozone, by contrast, is a pollutant.
| Convention or body |
Year |
Subject |
| Stockholm Conference |
1972 |
first global environment meet; led to UNEP and World Environment Day (5 June) |
| Ramsar Convention |
1971 |
conservation of wetlands |
| CITES |
1973 |
regulating trade in endangered species |
| Montreal Protocol |
1987 |
phasing out ozone-depleting substances (CFCs) |
| Basel Convention |
1989 |
transboundary movement of hazardous waste |
| Earth Summit, Rio |
1992 |
adopted the CBD and UNFCCC; Agenda 21 |
| Kyoto Protocol |
1997 |
binding emission cuts for developed nations |
| Cartagena Protocol |
2000 |
safe handling of living modified organisms |
| Paris Agreement |
2015 |
limit warming well below 2° Celsius; nationally determined contributions |
| IPCC |
UN body |
assesses the science of climate change |
| Law or body |
Year |
Subject |
| Wildlife (Protection) Act |
1972 |
protected species, parks and sanctuaries |
| Water (Prevention and Control of Pollution) Act |
1974 |
water pollution; created the CPCB |
| Forest (Conservation) Act |
1980 |
restricts diversion of forest land |
| Air (Prevention and Control of Pollution) Act |
1981 |
air pollution |
| Environment (Protection) Act |
1986 |
umbrella law passed after the Bhopal gas tragedy (1984) |
| National Green Tribunal Act |
2010 |
created the NGT for fast-track environmental adjudication |
| Central Pollution Control Board (CPCB) |
statutory |
sets and monitors pollution standards |
- Resource stress (water, land, forests) is a recognised driver of conflict and migration that feeds internal-security planning.
- Environmental crime is a frontline CAPF concern: wildlife smuggling, illegal mining, timber and sand trafficking, and cross-border poaching are tackled by the BSF, SSB and forest forces.
- Climate-linked disasters (floods, cyclones, landslides, glacial lake outbursts) increasingly draw the CAPFs and the National Disaster Response Force (NDRF) into relief operations.
- Bhopal gas tragedy (1984), a methyl isocyanate leak, is the disaster that prompted the Environment (Protection) Act 1986 and remains a stock industrial-hazard reference.
Q1The depletion of the ozone layer is mainly caused by
- Acarbon dioxide
- Bmethane
- Cchlorofluorocarbons
- Dnitrogen. Answer:
- C. CFCs release chlorine that destroys stratospheric ozone; carbon dioxide and methane cause warming, not depletion.
Q2According to the ten percent law, the energy passed from one trophic level to the next is about
- A1 percent
- B10 percent
- C50 percent
- D90 percent. Answer:
- B. Only about 10 percent of energy transfers up, so food chains are short.
Q3The Montreal Protocol (1987) deals with
- Aclimate change
- Bozone-depleting substances
- Cwetlands
- Dhazardous waste. Answer:
- B. It phases out CFCs and other ozone-depleting substances.
Q4The Environment (Protection) Act in India was passed in
- A1972
- B1981
- C1986
- D2010. Answer:
- C. The 1986 umbrella Act followed the 1984 Bhopal gas tragedy.
Q5Eutrophication of a water body refers to
- Adrying up
- Bnutrient over-enrichment causing algal blooms
- Cacidification
- Dsalt build-up. Answer:
- B. Excess nitrates and phosphates cause algal blooms and then oxygen depletion.
- Ozone depletion versus global warming: CFCs cause ozone-layer depletion; carbon dioxide and methane cause global warming. They are different problems addressed by different treaties (Montreal versus Paris and Kyoto).
- In-situ versus ex-situ conservation: in-situ is in the natural habitat (parks, sanctuaries); ex-situ is away from it (zoos, gene banks).
- National park versus wildlife sanctuary: a national park has the strictest protection; a sanctuary allows some regulated human activity.
- Stratospheric ozone versus ground-level ozone: stratospheric ozone is protective; ground-level ozone is a pollutant.
- Kyoto versus Paris: Kyoto (1997) set binding cuts for developed nations; Paris (2015) uses voluntary nationally determined contributions for all.
- Food chain versus food web: a food chain is a single linear sequence; a food web is many interlinked chains.
- "Montreal for the Moon-shaped ozone hole; Paris and Kyoto for the Planet's heat (climate)."
- Four Indian hotspots: "Himalaya, Western Ghats, Indo-Burma, Sundaland" (Hi-We-In-Su).
- "Ten percent climbs the ladder" for the ten percent law of energy transfer.
- Indian Acts by year: "Wildlife 72, Water 74, Forest 80, Air 81, Environment 86, NGT 2010."
- Producers make food, consumers eat, decomposers recycle; only about 10 percent of energy passes up a food chain.
- India has four biodiversity hotspots: the Himalaya, the Western Ghats, the Indo-Burma region and Sundaland.
- In-situ conservation is in parks and sanctuaries; ex-situ is in zoos and gene banks.
- CFCs deplete the ozone layer (Montreal Protocol 1987); carbon dioxide and methane drive global warming (Paris 2015, Kyoto 1997).
- Eutrophication is nutrient over-enrichment causing algal blooms; acid rain comes from sulphur and nitrogen oxides.
- The Environment (Protection) Act is 1986 (after Bhopal); the Wildlife Protection Act is 1972; the NGT Act is 2010; the CPCB sets standards.
- An ecosystem has biotic and abiotic components; producers, consumers and decomposers link in food chains.
- Only about 10 percent of energy passes from one trophic level to the next (the ten percent law).
- Biomagnification concentrates pollutants such as DDT and mercury up the food chain.
- India has four biodiversity hotspots: the Himalaya, the Western Ghats, the Indo-Burma region and Sundaland.
- In-situ conservation is in parks and sanctuaries; ex-situ is in zoos, gene banks and botanical gardens.
- The IUCN Red List ranks species from Least Concern to Critically Endangered to Extinct.
- CFCs deplete the stratospheric ozone layer; carbon dioxide and methane drive global warming.
- Eutrophication is nutrient over-enrichment causing algal blooms; acid rain comes from sulphur and nitrogen oxides.
- Stockholm 1972 led to UNEP and World Environment Day (5 June); Ramsar 1971 protects wetlands.
- The Rio Earth Summit 1992 adopted the CBD and UNFCCC; CITES governs trade in endangered species.
- The Montreal Protocol 1987 phases out CFCs; the Kyoto Protocol 1997 and Paris Agreement 2015 address climate change.
- The IPCC assesses the science of climate change.
- The Environment (Protection) Act 1986 is the umbrella law, passed after the 1984 Bhopal gas tragedy.
- The Wildlife Protection Act is 1972; the Water Act 1974 created the CPCB; the NGT was set up by the 2010 Act.
- Project Tiger began in 1973 and Project Elephant in 1992; Jim Corbett (1936) was India's first national park.
- Renewable energy includes solar, wind, hydro, biomass, geothermal and tidal; fossil fuels are non-renewable.
- India and France co-founded the International Solar Alliance; the UN SDGs run to 2030.
- Sustainable development meets present needs without compromising future generations.
- Ecosystem: a community of organisms interacting with their non-living environment.
- Trophic level: a step in a food chain (producer, herbivore, carnivore).
- Food chain: a linear sequence showing energy flow from one organism to the next.
- Decomposer: an organism that breaks down dead matter and recycles nutrients.
- Biodiversity: the variety of life at genetic, species and ecosystem levels.
- Biodiversity hotspot: a region rich in endemic species and under threat.
- In-situ conservation: protecting species in their natural habitat.
- Ex-situ conservation: protecting species away from their natural habitat.
- Eutrophication: nutrient over-enrichment of water causing algal blooms and oxygen loss.
- Greenhouse effect: the trapping of heat by atmospheric gases.
- Global warming: the long-term rise in average global temperature.
- Ozone layer: the stratospheric layer that absorbs harmful ultraviolet radiation.
- Biomagnification: the build-up of pollutants at higher levels of a food chain.
- Acid rain: rainfall acidified by sulphur and nitrogen oxides.