पर्यावरण और पारिस्थितिकी (बुनियादी)

हिंदी में पढ़ें

Environment & Ecology — The Web That Keeps Us Alive

◆ On the night of 2–3 December 1984, a poisonous gas called methyl isocyanate (MIC) leaked from the Union Carbide pesticide factory in Bhopal. Thousands of people died and many more suffered for life. It was one of the worst industrial disasters in the world. Two years later, Parliament passed the Environment (Protection) Act, 1986 — an "umbrella" law to protect air, water and land together. That one night taught India a hard lesson: when we harm the environment, the environment harms us back. In this chapter you will learn how nature is connected, how pollution breaks those connections, and which laws and treaties try to repair them.

What you will master today (Learning Objectives)

What an ecosystem is — producers, consumers, decomposers, food chains and food webs

The 10% law of energy and the three ecological pyramids

Biodiversity, hotspots, and in-situ vs ex-situ conservation

Air, water and soil pollution — the pollutant, the disease and the trap

Ozone depletion and the greenhouse effect — two different problems

Indian environmental laws and international conventions with their years

The examiner's favourite traps on this chapter, and simple hooks to beat them

PART A — ECOLOGY BASICS

1. Environment, Ecology and Ecosystem

Environment means everything around a living being — air, water, soil, light, and other living things.

Ecology is the study of how living organisms interact with each other and with their surroundings. The word was coined by the German biologist Ernst Haeckel.

Ecosystem: all the living things of an area together with the non-living things around them, working as one unit. The term was coined by A. G. Tansley in 1935. A pond, a forest, a grassland and even a garden are ecosystems. A crop field or an aquarium made by humans is an artificial ecosystem.

Every ecosystem has two kinds of parts:
Biotic (living) components — plants, animals, micro-organisms.
Abiotic (non-living) components — sunlight, temperature, rainfall, soil, water, minerals.

🧠 Active Recall: Who coined "ecology" and who coined "ecosystem"? (Haeckel — ecology; Tansley — ecosystem.)

2. Who Eats Whom — Producers, Consumers, Decomposers

Producers — green plants and algae. They make food by photosynthesis using sunlight. Also called autotrophs.

Consumers — animals that depend on others for food (heterotrophs).
Primary consumers = herbivores (deer, cow, grasshopper).
Secondary consumers = carnivores that eat herbivores (frog, fox).
Tertiary consumers = carnivores that eat other carnivores (snake, eagle).

Decomposers — bacteria and fungi. They break down dead plants and animals into simple substances and return nutrients to the soil. Without them the Earth would be covered with dead bodies and the soil would lose its minerals.

Food chain: a single line of "who eats whom".
Example: Grass → Grasshopper → Frog → Snake → Eagle.
Each step of a food chain is called a trophic level. Producers are the first trophic level; herbivores are the second.

Food web: many food chains linked together. Real ecosystems have food webs, because most animals eat more than one kind of food.

Grazing food chain starts with green plants; detritus food chain starts with dead organic matter (detritus).

🧠 Active Recall: When you eat a plate of dal-chawal, which trophic level are you on? (Second — you are a primary consumer.)

3. The 10% Law and Energy Flow

The Sun is the source of energy for almost every ecosystem. Green plants capture only a small part of the sunlight falling on them.

When one organism eats another, only about 10% of the energy is passed on to the next trophic level. The rest is used for the animal's own life processes and is lost mostly as heat. This is called the 10% law (given by Raymond Lindeman, 1942).

Example: If plants hold 10,000 J of energy, herbivores get about 1,000 J, the next carnivores about 100 J, and the top carnivores only about 10 J. This is why food chains usually have only 3–4 or 5 steps.

Energy flow is unidirectional — it moves from the Sun to producers to consumers and never comes back. Nutrients (carbon, nitrogen, phosphorus) are cyclic — decomposers return them to the soil to be used again.

Mnemonic: "Energy is a one-way ticket; nutrients take a return ticket."

4. Ecological Pyramids

A pyramid shows each trophic level as a step, with producers at the base.

Pyramid of numbers — counts the organisms. In a grassland it is upright (many grass plants, fewer grasshoppers, still fewer frogs). For a big tree with many insects on it, it is inverted.

Pyramid of biomass — weighs the living matter. On land it is upright. In the sea it is inverted, because the tiny phytoplankton at the base weigh less at any one time than the fish that feed on them.

Pyramid of energy — always upright. It can never be inverted, because energy is lost at every step.

🧠 Active Recall: Which pyramid can never be inverted? (Pyramid of energy.)

5. Biogeochemical Cycles in Brief

Nitrogen makes up about 78% and oxygen about 21% of the air. But plants cannot use nitrogen gas directly.

Nitrogen fixation: Rhizobium bacteria in the root nodules of leguminous plants (pea, gram, beans) change atmospheric nitrogen into compounds plants can use. Lightning also fixes some nitrogen. Denitrifying bacteria return nitrogen to the air.

Carbon cycle: plants take in carbon dioxide during photosynthesis; respiration, decay and burning of fuels return it to the air.

Ecological succession: the gradual change of communities in an area over time. On a bare rock, lichens are the pioneer species; the final stable community is called the climax community.

PART B — BIODIVERSITY AND CONSERVATION

6. Biodiversity

Biodiversity means the variety of life — genes, species and ecosystems. NCERT notes that India has only about 2.4% of the world's land area, but about 8.1% of the world's recorded species diversity. India is one of the 17 megadiverse countries.

Biodiversity hotspots are regions very rich in species, with many endemic species (found nowhere else), and under serious threat. The idea was given by Norman Myers. The hotspots that cover parts of India are: the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland (which includes the Nicobar Islands).

Why biodiversity is lost — the "Evil Quartet" (NCERT Class 12):

1. Habitat loss and fragmentation (the biggest cause)
2. Over-exploitation (e.g. Steller's sea cow and the passenger pigeon were hunted to extinction)
3. Alien species invasions (e.g. Nile perch in Lake Victoria; weeds like Parthenium, Lantana and water hyacinth in India)
4. Co-extinctions (when a host dies out, its special parasites die out too)

Extinct examples asked in exams: Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller's sea cow (Russia). The cheetah was declared extinct in India in 1952.

🧠 Active Recall: Name the four causes of the "Evil Quartet". (Habitat loss, over-exploitation, alien invasions, co-extinctions.)

7. Conservation: In-situ and Ex-situ

In-situ conservation = protecting species in their natural home. Examples: national parks, wildlife sanctuaries, biosphere reserves, sacred groves.

Ex-situ conservation = protecting species outside their natural home. Examples: zoos, botanical gardens, seed banks, gene banks, cryopreservation.

Mnemonic: "IN-situ = IN the jungle; EX-situ = EXit the jungle."

A biosphere reserve has three zones: core zone (fully protected, no human activity), buffer zone (limited activities like research and education), and transition zone (people live and work). The Nilgiri Biosphere Reserve (1986) was India's first biosphere reserve. Biosphere reserves are linked to UNESCO's Man and the Biosphere (MAB) programme.

Sacred groves — patches of forest protected by communities for religious reasons, e.g. in the Khasi and Jaintia Hills (Meghalaya), the Aravalli hills of Rajasthan, and the Western Ghats.

8. Protected Areas and Species Projects

First national park of India: Hailey National Park (1936), now called Jim Corbett National Park, Uttarakhand.

Famous parks and their animals:
Gir (Gujarat) — Asiatic lion
Kaziranga (Assam) — one-horned rhinoceros
Sundarbans (West Bengal) — Royal Bengal tiger in a mangrove forest (named after the Sundari tree)
Dachigam (Jammu & Kashmir) — Hangul (Kashmir stag)
Keibul Lamjao (Manipur) — Sangai deer; the only floating national park, on Loktak Lake
Keoladeo (Bharatpur, Rajasthan) — birds; once famous for the Siberian crane
Silent Valley (Kerala) — lion-tailed macaque
Eravikulam (Kerala) — Nilgiri tahr
Desert National Park (Rajasthan) — Great Indian Bustard (critically endangered)
Gahirmatha coast (Odisha) — mass nesting of Olive Ridley turtles

Species projects:
Project Tiger — launched in 1973. The tiger was made the national animal in 1973. Tiger reserves are now notified under the Wildlife (Protection) Act, 1972, as amended in 2006, which created the National Tiger Conservation Authority (NTCA).
Project Elephant — launched in 1992. The elephant was declared the National Heritage Animal in 2010.
Gangetic river dolphin — National Aquatic Animal (2009).

🧠 Active Recall: Which national park floats? (Keibul Lamjao, on Loktak Lake, Manipur.)

9. People Who Saved Forests

Bishnoi community (Rajasthan): In 1730 at Khejarli (near Jodhpur), Amrita Devi Bishnoi and many villagers gave their lives to save Khejri trees.
Chipko Movement (1973): Began in Chamoli district (now in Uttarakhand). Villagers hugged trees to stop felling. Leaders: Sunderlal Bahuguna, Chandi Prasad Bhatt; Gaura Devi led the women of Reni village.
Appiko Movement (1983): Karnataka — "Chipko of the south", led by Panduranga Hegde.
Silent Valley Movement (Kerala): stopped a hydroelectric project; Silent Valley became a national park in 1984.
Narmada Bachao Andolan: led by Medha Patkar, against large dams on the Narmada.
Joint Forest Management (JFM): involves local communities in managing and restoring degraded forests; Odisha passed the first resolution in 1988.

PART C — POLLUTION

10. Air Pollution

Pollutant = any substance that harms living things when present in the wrong place or amount.
Primary pollutants are released directly (sulphur dioxide, carbon monoxide, nitrogen oxides, smoke).
Secondary pollutants are formed in the air from primary ones (ground-level ozone, PAN in photochemical smog, acid rain).

Carbon monoxide (CO) — from incomplete burning; it binds to haemoglobin much more strongly than oxygen and reduces the blood's ability to carry oxygen.
Sulphur dioxide (SO2) and nitrogen oxides (NOx) — cause acid rain. Acid rain corrodes marble; NCERT notes that the marble of the Taj Mahal is being damaged ("marble cancer") by pollutants from industries around Agra and Mathura.
Smog = smoke + fog.
Lichens are good indicators of air pollution — they do not grow in areas with high sulphur dioxide.
PM2.5 = fine particles with diameter of 2.5 micrometres or less; they go deep into the lungs.
Catalytic converters in vehicles reduce poisonous exhaust gases. CNG is a cleaner fuel than petrol and diesel.

11. Water and Soil Pollution

Eutrophication: When fertilisers (nitrates and phosphates) and sewage reach a lake, algae grow very fast (algal bloom). When the algae die, decomposers use up the dissolved oxygen, and fish die.

BOD (Biochemical Oxygen Demand): the oxygen needed by microbes to break down organic matter in water. High BOD = more organic pollution. Clean water has low BOD.

Biological magnification: Harmful non-biodegradable chemicals like DDT and mercury enter the food chain and their concentration increases at every higher trophic level. Top carnivores (and humans) get the highest dose.

Pollutant–disease pairs (very important):
Mercury → Minamata disease (Japan)
Cadmium → Itai-itai disease (Japan)
Nitrate in drinking water → Blue baby syndrome
Excess fluoride → Fluorosis (teeth and bones)
Arsenic → Blackfoot disease and skin problems
Lead → damage to nerves and the brain, especially in children

Noise is measured in decibels (dB).

Biodegradable substances are broken down by microbes (vegetable peels, paper, cotton). Non-biodegradable substances are not (plastic, glass, DDT, aluminium cans). Habits that help: Reduce, Reuse, Recycle.

🧠 Active Recall: Mercury and cadmium both caused diseases in Japan. Which is which? (Mercury — Minamata; Cadmium — Itai-itai.)

PART D — OZONE AND CLIMATE

12. The Ozone Layer

Ozone (O3) in the stratosphere forms the ozone layer, which absorbs harmful ultraviolet (UV) radiation from the Sun. UV rays can cause skin cancer, cataract and damage to plants.

Ozone near the ground (in the troposphere) is a harmful pollutant — "good up high, bad nearby".

Chlorofluorocarbons (CFCs), used in refrigerators, air-conditioners and sprays, reach the stratosphere, where UV light breaks them and releases chlorine atoms. Chlorine destroys ozone. The thinning is greatest over Antarctica — the "ozone hole".

Ozone thickness is measured in Dobson Units (DU).

Treaties: Vienna Convention (1985) — the framework; Montreal Protocol (signed 16 September 1987) — phases out ozone-depleting substances; Kigali Amendment (2016) — adds the phase-down of HFCs. World Ozone Day: 16 September.

13. The Greenhouse Effect and Global Warming

Some gases in the air trap the heat given out by the Earth, like the glass of a greenhouse. Without any greenhouse effect, the Earth would be far too cold for life.

Main greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), CFCs and water vapour. Nitrogen (N2) and oxygen (O2) are NOT greenhouse gases.

Carbon dioxide makes the largest contribution to global warming. Methane comes from paddy fields, cattle, wetlands and garbage dumps.

Effects of global warming: melting glaciers, rising sea level, coral bleaching (corals lose their colourful algae when sea water gets too warm), changes in rainfall and more extreme weather.

Mnemonic: "Ozone hole = Umbrella torn (UV comes in). Greenhouse = Blanket too thick (heat stays in)."

🧠 Active Recall: Is ozone depletion the same as global warming? (No — one lets UV in, the other traps heat. CFCs play a part in both.)

PART E — LAWS AND TREATIES

14. Environment in the Constitution

The 42nd Amendment (1976) added:
Article 48A — Directive Principle: the State shall try to protect and improve the environment and safeguard forests and wildlife.
Article 51A(g) — Fundamental Duty: every citizen shall protect and improve the natural environment, including forests, lakes, rivers and wildlife.
It also moved "forests" and "protection of wild animals and birds" from the State List to the Concurrent List.

15. Indian Environmental Laws (with years)

Wildlife (Protection) Act — 1972
Water (Prevention and Control of Pollution) Act — 1974 (the Central Pollution Control Board was set up under it)
Forest (Conservation) Act — 1980 (renamed Van (Sanrakshan Evam Samvardhan) Adhiniyam, 1980 by an amendment in 2023)
Air (Prevention and Control of Pollution) Act — 1981
Environment (Protection) Act — 1986 (after the Bhopal gas tragedy; an umbrella law)
Biological Diversity Act — 2002 (National Biodiversity Authority, Chennai)
Forest Rights Act — 2006 (rights of tribal and forest-dwelling communities)
National Green Tribunal Act — 2010 (NGT set up in October 2010; principal bench in New Delhi)

The Ministry of Environment and Forests was created in 1985; "Climate Change" was added to its name in 2014 (MoEFCC). The Forest Survey of India (Dehradun) publishes the India State of Forest Report every two years. The National Forest Policy, 1988 aims to bring one-third (33%) of India's area under forest or tree cover.

Mnemonic for the order of the Acts: "Wild Water Forest Air Environment" — 72, 74, 80, 81, 86. Read it as "Wild animals drink Water, live in the Forest, breathe Air — that is the Environment."

16. International Conventions (with years)

Ramsar Convention (1971) — wetlands; signed at Ramsar, Iran. World Wetlands Day: 2 February. India joined in 1982; Chilika Lake (Odisha) and Keoladeo (Rajasthan) were India's first Ramsar sites (1981). The Montreux Record lists Ramsar sites where the ecology has changed or is likely to change for the worse.
Stockholm Conference (1972) — first UN conference on the human environment; led to UNEP (headquarters Nairobi, Kenya). World Environment Day (5 June) marks its opening day.
CITES (1973) — controls international trade in endangered wild animals and plants; signed at Washington, D.C.; India became a party in 1976. World Wildlife Day (3 March) marks the day it was signed.
Vienna Convention (1985) and Montreal Protocol (1987) — ozone layer.
Basel Convention (1989) — movement of hazardous wastes across borders.
Rio Earth Summit (1992) — UNFCCC (climate), Convention on Biological Diversity (CBD), Agenda 21.
Kyoto Protocol (1997) — legally binding targets for developed countries to cut greenhouse gases; came into force in 2005.
Paris Agreement (2015, COP21) — keep the rise in global temperature well below 2°C above pre-industrial levels and try to limit it to 1.5°C; came into force in 2016.

Other names to know: IUCN (Gland, Switzerland) publishes the Red List (Red Data Book) of threatened species. IPCC was set up in 1988 by WMO and UNEP. The Brundtland Report "Our Common Future" (1987) defined sustainable development: meeting today's needs without harming the ability of future generations to meet theirs.

Mnemonic for conventions in order: "Real Clever Villagers Make Rich Kings Proud" — Ramsar 1971, CITES 1973, Vienna 1985, Montreal 1987, Rio 1992, Kyoto 1997, Paris 2015.

Green days calendar:
2 February — World Wetlands Day | 3 March — World Wildlife Day | 21 March — International Day of Forests | 22 March — World Water Day | 22 April — Earth Day | 22 May — International Day for Biological Diversity | 5 June — World Environment Day | 16 September — World Ozone Day | 2 December — National Pollution Control Day (India, in memory of Bhopal)

Summary Table

⏰ Review this chapter after 2 days.

⚠️ Caution: Examiner's Trap

Trap 1 — "Similar Name": Montreal vs Kyoto. Montreal Protocol (1987) = ozone layer. Kyoto Protocol (1997) = greenhouse gases. Also Minamata (mercury) vs Itai-itai (cadmium); nitrogen (not a greenhouse gas) vs nitrous oxide (a greenhouse gas).

Trap 2 — "Almost True Statement": "The pyramid of biomass is always upright." Almost right — on land it is, but in the sea it is inverted. Only the pyramid of energy is always upright.

Trap 3 — "Chronological Confusion": Bhopal tragedy 1984 → Environment (Protection) Act 1986. Students mix up 1984 and 1986, or think the Air Act (1981) came before the Forest Act (1980).

Trap 4 — "Negative Phrasing": "Which of these is NOT an in-situ method?" — the answer is the zoo/botanical garden/seed bank. Read "NOT" twice.

Trap 5 — "Reverse Causation": "Global warming causes the ozone hole." Wrong — the ozone hole is caused mainly by CFCs, and it lets UV rays in; global warming is caused by greenhouse gases trapping heat.

🔁 Linguistic Bridge: In Hindi we say this, in English we say that

पारितंत्र / पारिस्थितिक तंत्र — Ecosystem
पारिस्थितिकी — Ecology
उत्पादक / उपभोक्ता / अपघटक — Producer / Consumer / Decomposer
पोषी स्तर — Trophic level
खाद्य श्रृंखला / खाद्य जाल — Food chain / Food web
जैव आवर्धन — Biological magnification
सुपोषण — Eutrophication
जैव विविधता — Biodiversity
स्वस्थाने / बाह्य-स्थाने संरक्षण — In-situ / Ex-situ conservation
जैवमंडल आरक्षित क्षेत्र — Biosphere reserve
आर्द्रभूमि — Wetland
समताप मंडल / क्षोभ मंडल — Stratosphere / Troposphere
हरितगृह प्रभाव — Greenhouse effect
अम्लीय वर्षा — Acid rain
जैव-निम्नीकरणीय — Biodegradable

🔗 Static-Dynamic Link

Ramsar sites: As announced by PIB on 3 August 2026, Glaw Lake (Arunachal Pradesh's first Ramsar site) became India's 101st Ramsar site. (India had 26 Ramsar sites in 2014.) This number keeps growing — check the latest figure before your exam.

Tiger reserves: According to the Ministry's Year-end Review (PIB, December 2025), India had 58 tiger reserves; the 58th, Madhav Tiger Reserve in Madhya Pradesh, was notified in March 2025.

Project Cheetah: On 17 September 2022, cheetahs brought from Namibia were released in Kuno National Park, Madhya Pradesh — 70 years after the cheetah was declared extinct in India (1952).

Climate pledge: At COP26 in Glasgow (1 November 2021), India announced the target of net-zero emissions by 2070.

Forest law: In 2023, the Forest (Conservation) Act, 1980 was renamed the Van (Sanrakshan Evam Samvardhan) Adhiniyam, 1980.

📅 Revision Planner: Three-Level Blurting

🔢 High-Yield Facts & Figures (Quick Glance)

Everything you breathe, drink and eat comes through this web of life. Learn it as a story — Sun to plant, plant to animal, animal back to soil — and every exam question on this chapter becomes a question about a story you already know.