Environment and Ecology: key facts and practice questions

Revise Environment and Ecology for SSC, Railway, police and state PSC exams: the facts and distinctions that keep coming up, a one-glance revision list, and 10 practice questions with answers and explanations.

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Key concepts and facts

• Ecosystem basics: Ecology (term by Ernst Haeckel, 1866) studies organisms and their environment; the term ecosystem was given by A.G. Tansley in 1935. An ecosystem has abiotic components (sunlight, temperature, water, soil) and biotic components: producers (green plants), consumers and decomposers (bacteria, fungi). Energy flows one way through trophic levels and only about 10 percent passes to the next level (Lindeman's 10 percent law). A grazing food chain starts with green plants, a detritus food chain with dead organic matter; interlinked chains form a food web. The pyramid of energy is always upright, the pyramid of biomass is inverted in a pond and the pyramid of numbers is inverted for a single tree supporting thousands of insects. A habitat is the address of a species, a niche its functional role. An ecotone is the transition zone between two ecosystems and shows the edge effect, a greater number of species. In succession, lichens are pioneers on bare rock and a stable climax community comes last. A keystone species has an effect out of proportion to its numbers.
• Cycles and aquatic systems: Rhizobium (in legume root nodules) and Azotobacter (free-living) fix nitrogen; Nitrosomonas converts ammonia to nitrite and Nitrobacter nitrite to nitrate; Pseudomonas returns nitrogen to the air (denitrification). The phosphorus cycle is sedimentary with no gaseous phase. Enrichment of water with nitrates and phosphates causes algal bloom, called eutrophication; a high BOD means heavy organic pollution. Mangroves (Sundarbans is the largest) have breathing roots called pneumatophores; corals live with symbiotic algae (zooxanthellae) and bleach when the sea warms; Chilika in Odisha is Asia's largest brackish water lagoon.
• Biodiversity: Norman Myers gave the hotspot concept in 1988; a hotspot needs at least 1,500 endemic vascular plants and 70 percent habitat loss. India has parts of four hotspots: Himalaya, Indo-Burma, Western Ghats-Sri Lanka and Sundaland (Nicobar), and is one of 17 megadiverse countries. IUCN Red List categories run Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern. A flagship species (tiger) wins public support; an umbrella species (elephant) shelters many others. Animal-park pairs: rhino at Kaziranga, Asiatic lion only at Gir, hangul at Dachigam, barasingha at Kanha, Nilgiri tahr at Eravikulam, wild ass in the Little Rann of Kutch, Great Indian Bustard (state bird of Rajasthan) in the Desert National Park.
• Conservation: In-situ conservation protects species in their natural home (national parks, sanctuaries, biosphere reserves, conservation and community reserves); ex-situ conservation moves them out (zoos, botanical gardens, seed banks). No human activity is allowed in a national park, while limited rights may continue in a sanctuary. A biosphere reserve (UNESCO Man and Biosphere programme, 1971) has core, buffer and transition zones; Nilgiri (1986) was India's first. Jim Corbett (Hailey) National Park, 1936, was the first national park. Project Tiger began in 1973, the Crocodile project in 1975, Project Elephant in 1992 and Project Snow Leopard in 2009. The drug diclofenac caused the vulture crash of the 1990s. The Ramsar Convention on wetlands (Iran, 1971) keeps a Montreux Record of threatened wetlands. The Gadgil panel (2011) wanted the whole Western Ghats declared ecologically sensitive; the Kasturirangan panel (2013) cut this to about 37 percent.
• Laws and institutions: Wildlife (Protection) Act 1972 (Schedule I gives the highest protection), Water Act 1974 (created the CPCB and SPCBs), Forest (Conservation) Act 1980, renamed the Van (Sanrakshan Evam Samvardhan) Adhiniyam by the 2023 amendment (Central approval to divert forest land), Air Act 1981, Environment (Protection) Act 1986 (umbrella law after the Bhopal gas tragedy of 1984), Biological Diversity Act 2002 (National Biodiversity Authority, Chennai), Forest Rights Act 2006 and National Green Tribunal Act 2010. The National Board for Wildlife is chaired by the Prime Minister. Articles 48A and 51A(g) came with the 42nd Amendment, 1976.
• Pollution: London smog (1952) was sulphurous smog from coal; photochemical smog forms from nitrogen oxides and hydrocarbons in sunlight, producing ozone and PAN. Acid rain comes from sulphur dioxide and nitrogen oxides. Minamata disease is mercury, itai-itai is cadmium, blue baby syndrome is nitrate, fluorosis is fluoride, and arsenic contaminates groundwater in West Bengal. Bhopal (1984) released methyl isocyanate; Chernobyl (1986) was a nuclear accident in Ukraine. Biomagnification is the rise in concentration of a persistent toxin such as DDT along the food chain. India's AQI uses eight pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3 and lead.
• Climate change and conventions: Carbon dioxide contributes most to warming, methane comes from paddy and cattle, CFCs and SF6 have very high global warming potential. The IPCC was set up in 1988 by WMO and UNEP. The Rio Earth Summit (1992) produced the UNFCCC and the CBD; the Kyoto Protocol (1997, COP3) bound developed Annex I countries; the Paris Agreement (2015, COP21) keeps warming well below 2 degrees Celsius, pursuing 1.5, through each country's NDCs. The Montreal Protocol (1987) phases out ozone-depleting substances and its Kigali Amendment (2016) phases down HFCs. One carbon credit equals one tonne of CO2 equivalent. Remember CITES 1973 (wildlife trade), Bonn 1979 (migratory species), Basel 1989 (hazardous waste), Rotterdam 1998 (chemicals trade), Stockholm 2001 (persistent organic pollutants), Minamata 2013 (mercury), and under the CBD the Cartagena (biosafety) and Nagoya (benefit sharing) protocols. UNEP (Nairobi) dates from the Stockholm Conference of 1972, after which 5 June became World Environment Day.
• Movements, energy and sustainability: Chipko (1973, Chamoli), Silent Valley (Kerala), Appiko (Karnataka, 1983), Narmada Bachao Andolan (Medha Patkar) and Khejarli (1730, Amrita Devi) are the standard movement questions. Biofuel generations run food crops, non-food biomass, algae and engineered organisms; green hydrogen comes from electrolysis using renewable power; the Gulfs of Kutch and Khambhat hold India's tidal potential. The Brundtland Report (1987) defined sustainable development; the UN adopted 17 SDGs in 2015 for 2030.
• Common traps: Montreal is ozone, Kyoto and Paris are climate; Minamata is mercury but itai-itai is cadmium; Project Tiger is 1973 but the Wildlife Act is 1972; the Stockholm Conference is 1972 but the Stockholm Convention is 2001; the CPCB comes from the Water Act, not the Air Act.

One-glance revision list

• IUCN ladder from most to least threatened: EX, EW, CR, EN, VU, NT, LC (Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern).
• Year ladder: Wildlife Act 1972, Project Tiger 1973, Water Act 1974, Forest (Conservation) Act 1980 (renamed Van Adhiniyam in 2023), Air Act 1981, Bhopal 1984, EPA 1986, Project Elephant 1992, Biodiversity Act 2002, FRA 2006, NGT 2010.
• Montreal 1987 = ozone (CFCs); Kyoto 1997 = greenhouse gases, binding only for developed Annex I countries; Paris 2015 = all countries, NDCs, well below 2 degrees Celsius.
• Disease-pollutant pairs: Minamata = mercury, itai-itai = cadmium, blue baby syndrome = nitrate, fluorosis = fluoride, black foot disease = arsenic.
• Animal-park pairs: rhino-Kaziranga, lion-Gir, hangul-Dachigam, barasingha-Kanha, Nilgiri tahr-Eravikulam, wild ass-Little Rann of Kutch, snow leopard-Hemis.
• Nitrogen cycle bacteria: Rhizobium fixes nitrogen, Nitrosomonas makes nitrite, Nitrobacter makes nitrate, Pseudomonas denitrifies it back to the air.
• Inverted pyramids: biomass in a pond, numbers on a single tree; the pyramid of energy is always upright because of the 10 percent law.
• India's four hotspots: Himalaya, Indo-Burma, Western Ghats-Sri Lanka, Sundaland (Nicobar). The Eastern Ghats and the Aravalli are NOT hotspots.
• Stockholm 1972 = UN conference that created UNEP and World Environment Day; Stockholm 2001 = convention on persistent organic pollutants. Same city, different question.
• Chemical conventions in order B-R-S-M: Basel (hazardous waste), Rotterdam (prior informed consent for chemical trade), Stockholm (POPs), Minamata (mercury).
• Days: 2 Feb Wetlands, 3 Mar Wildlife, 21 Mar Forests, 22 Mar Water, 22 Apr Earth, 22 May Biodiversity, 5 Jun Environment, 16 Sep Ozone.
• Movements: Chipko 1973 Uttarakhand (hug the trees), Appiko 1983 Karnataka (its southern echo), Silent Valley Kerala (dam stopped), Narmada Bachao (Medha Patkar), Khejarli 1730 Bishnoi (Amrita Devi).

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