Environmental Science & Ecology

Environmental Science & Ecology

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

• Ecology is the branch of biology that examines interactions between organisms and their abiotic (non-living: light, water, temperature, soil) and biotic (living) environment; Environmental Science is the broader interdisciplinary field covering pollution, resource use, and policy.
• Lindeman’s 10% Law: only about 10% of the energy at one trophic level (producer → primary consumer → secondary → tertiary) is transferred to the next; the rest is lost as heat via respiration.
• Population density D = N / A, where N = total individuals, A = area. Growth rate r = b − d (natality minus mortality). Exponential growth: Nₜ = N₀ eʳᵗ.
• Pyramid of energy is always upright; pyramid of numbers can be inverted (e.g., one tree supporting thousands of insects).
• High-yield for UPPSC PCS: Chipko Movement (1973, Sundarlal Bahuguna), Project Tiger (1973), Montreal Protocol (1987) for CFCs, Kyoto (1997), Paris Agreement (2015), Wildlife Protection Act 1972, Forest Conservation Act 1980, Ramsar Convention (wetlands), and World Environment Day – June 5.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Ecosystem Structure and Function

An ecosystem comprises biotic components (producers, consumers — primary, secondary, tertiary, decomposers) and abiotic components (sunlight, temperature, water, soil, minerals). Two key processes run in parallel: energy flow (unidirectional, non-cyclic) and nutrient cycling (biogeochemical cycles — cyclic).

Energy Flow and Lindeman’s Law

Primary producers (green plants) fix solar energy via photosynthesis. At each successive trophic level, only ~10% of energy is assimilated into biomass; ~90% is lost as metabolic heat, following the second law of thermodynamics. Hence a pyramid of energy is always upright, while a pyramid of numbers may be inverted (parasitic/ tree-based food chains) and a pyramid of biomass is upright in terrestrial ecosystems but inverted in aquatic ecosystems (phytoplankton biomass < zooplankton).

Pyramid type	Shape in terrestrial	Shape in aquatic
Number	Upright (sometimes inverted)	Generally inverted
Biomass	Upright	Inverted
Energy	Always upright	Always upright

Biogeochemical Cycles

Key cycles to memorise for UPPSC:

• Water cycle: evaporation → condensation → precipitation → infiltration.
• Carbon cycle: photosynthesis fixes CO₂; respiration and combustion release it; fossil fuels act as long-term sinks.
• Nitrogen cycle: fixation (Rhizobium, lightning) → nitrification (Nitrosomonas, Nitrobacter) → assimilation → ammonification → denitrification (Pseudomonas).
• Phosphorus cycle: sedimentary, no gaseous phase — key reason for eutrophication in lakes.

Ecological Succession

Primary succession starts on a bare area (lava, rock); secondary succession follows disturbance where soil persists (e.g., after fire). The sequence moves from pioneer community → seral stages → climax community (relatively stable).

Population Ecology

• Natality (b) = births/population × 1000; Mortality (d) = deaths/population × 1000.
• Exponential growth (J-shaped curve) under unlimited resources: Nₜ = N₀ eʳᵗ.
• Logistic growth (S-shaped curve) under resource limitation: dN/dt = rN(K − N)/K, where K = carrying capacity.

Biodiversity

Three levels: genetic, species, ecosystem. India hosts 4 of the 34 global biodiversity hotspots: Western Ghats, Himalaya, Indo-Burma, Sundaland. Conservation is in-situ (national parks, wildlife sanctuaries, biosphere reserves) and ex-situ (zoos, seed banks, cryopreservation).

Pollution

• Air: SPM, PM2.5, PM10, SO₂, NOₓ, CO, lead. BOD (Biochemical Oxygen Demand) measures organic pollution in water; high BOD = polluted.
• Eutrophication: nutrient enrichment (N, P) → algal bloom → oxygen depletion → fish kill.
• Bioaccumulation = buildup in one organism; Biomagnification = increasing concentration up the food chain (e.g., DDT, mercury).

Climate Change

Greenhouse gases: CO₂, CH₄, N₂O, CFCs, water vapour. Global warming potential: CO₂ = 1, CH₄ ≈ 25×, N₂O ≈ 298×. Ozone depletion is caused by CFCs releasing chlorine radicals in the stratosphere — controlled by the Montreal Protocol, 1987.

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Edge Cases and Examiner Traps

• Food chain vs food web: a food chain is linear (grass → deer → tiger); a food web is the network of multiple interlinked chains. UPPSC often asks which is “more stable” — answer: the food web, because the loss of one species can be compensated.
• Pyramid of energy is ALWAYS upright (a strict consequence of the 10% law). Never claim it can be inverted; that mistake is exploited in MCQs.
• Keystone species (e.g., sea otter, tiger) have a disproportionately large effect on ecosystem structure relative to their abundance — remove them and community structure collapses.
• Endemic species are geographically restricted (e.g., Nilgiri tahr, Lion-tailed macaque, Asiatic lion in Gir). Cosmopolitan species occur worldwide (e.g., humans, house rat).
• Carrying capacity (K) is dynamic, not fixed: it shifts with season, technology, and resource availability.

Important Indian Legislation and Initiatives

• Wildlife Protection Act, 1972 — gave legal status to Schedules I–VI; Schedule I species get highest protection.
• Forest Conservation Act, 1980 — restricts diversion of forest land for non-forest use.
• Environment Protection Act, 1986 — umbrella act after Bhopal disaster.
• Project Tiger (1973): launched at Jim Corbett National Park; currently 50+ reserves.
• Project Elephant (1992), Crocodile Conservation Project (1975), Project Cheetah (2022, Kuno National Park).
• Chipko Movement (1973) — led by Sundarlal Bahuguna and Gaura Devi in Uttarakhand; pre-Rio global example of grassroots environmentalism.

International Agreements

• Stockholm (1972) — first UN conference on human environment.
• Ramsar Convention (1971) — wetlands of international importance; India has 80+ Ramsar sites (renowned: Chilika, Wular, Loktak, Sambhar, Keoladeo Ghana).
• CITES (1975) — trade in endangered species.
• Kyoto Protocol (1997) — binding emission reduction targets for Annex I countries.
• Paris Agreement (2015) — limit warming to 1.5–2 °C above pre-industrial levels; NDCs (Nationally Determined Contributions).
• CBD (1992, Rio Earth Summit) — three objectives: conservation, sustainable use, fair equitable benefit sharing (Nagoya Protocol).

Practice Prompts

1. Worked numerical: A grassland has 5,000 deer. In one year 1,200 births and 400 deaths occur. Compute natality, mortality, and growth rate. → b = 1,200/5,000 × 1000 = 240 per 1000; d = 400/5,000 × 1000 = 80 per 1000; r = 160 per 1000 (positive growth).
2. Conceptual: A lake receives phosphate-rich runoff. Explain, step by step, how this leads to fish mortality, naming the process. → Phosphate enrichment → algal bloom → light blockage to submerged plants → death of plants → aerobic decomposers consume dissolved O₂ → BOD rises sharply → fish suffocate. This is cultural eutrophication.
3. Assertion-Reason style: “Energy pyramid is always upright” (A) because “only 10% energy transfers between trophic levels” (R). Mark: Both true, R is the correct explanation of A.

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