Ecology & Environment
Key Concepts
| # | Concept | Explanation |
|---|---|---|
| 1 | Ecosystem | A biological community of interacting organisms and their physical environment; always has producers, consumers, decomposers. |
| 2 | Food Chain vs Web | Chain = single linear path of energy; Web = inter-connected chains giving stability. |
| 3 | 10 % Law | Only ~10 % of energy is passed to next trophic level—rest lost as heat—explains why food chains are short. |
| 4 | Biogeochemical Cycles | Natural pathways by which essential elements (C, N, P, H₂O) move between biotic & abiotic parts. |
| 5 | BOD & COD | Biological Oxygen Demand ↑ = more organic pollution; Chemical Oxygen Demand ↑ = chemical pollution. |
| 6 | Ozone Hole | Caused mainly by CFCs (chlorine release) over Antarctica; increases UV-B radiation → skin cancer. |
| 7 | Carbon Credit | 1 credit = 1 tonne CO₂ eq. reduced; tradable permit under Kyoto/Paris mechanisms. |
| 8 | IUCN Red List | Inventory of global conservation status; categories: CR > EN > VU > NT > LC. |
15 Practice MCQs
The energy pyramid is always upright because— A. Energy increases upwards
B. Energy remains constant
C. Energy decreases upwards
D. Energy becomes zero at top
Answer: C
Solution: 10 % law → progressive loss, so top level has least energy.
Shortcut: Pyramid “narrows” = energy “shrinks”.
Tag: Energy flowMontreal Protocol is related to— A. Biodiversity loss
B. Ozone depletion
C. Climate change
D. Wetland conservation
Answer: B
Solution: Signed 1987 to phase out ODS (CFCs, halons).
Shortcut: “Mont” ≈ “Mountain” ≈ “Ozone layer on top”.
Tag: International conventionsWhich is a primary pollutant? A. PAN
B. O₃
C. SO₂
D. H₂SO₄
Answer: C
Solution: SO₂ directly emitted from fossil fuels; others formed in air.
Shortcut: Primary = “first hand smoke”.
Tag: Air pollutionBOD of healthy river water should be below— A. 5 ppm
B. 17 ppm
C. 50 ppm
D. 150 ppm
Answer: A
Solution: <5 ppm = clean; >17 ppm = heavily polluted.
Shortcut: “5 fingers keep river alive”.
Tag: Water qualityThe term ‘Green Accounting’ means— A. Using green ink in ledgers
B. Including environmental costs in GDP
C. Plantation on highways
D. Green bond trading
Answer: B
Solution: Natural resource depletion & degradation are monetised & subtracted.
Tag: Sustainable developmentWhich biome has highest species diversity per unit area? A. Tundra
B. Tropical rainforest
C. Temperate grassland
D. Taiga
Answer: B
Solution: Constant warmth & moisture → year-round growth & niches.
Shortcut: “Rain = Richness”.
Tag: BiodiversityMinamata disease is caused by— A. Pb
B. Hg
C. As
D. Cd
Answer: B
Solution: Methyl-mercury bio-accumulation from factory effluent in Japan.
Shortcut: “MeHg” → “MinHgata”.
Tag: Pollution diseasesKyoto Protocol’s first commitment period was— A. 1990-2000
B. 2000-2010
C. 2008-2012
D. 2015-2020
Answer: C
Solution: Annex-I countries cut GHGs 5 % below 1990 levels.
Tag: Climate agreementsThe carnivore acting both as secondary & tertiary consumer is— A. Tiger
B. Snake (eats frog & rat)
C. Cow
D. Phytoplankton
Answer: B
Solution: Snake → secondary when eats herbivore (rat); tertiary when eats carnivore (frog).
Tag: Food webWhich is NOT an in-situ conservation method? A. Biosphere reserve
B. National park
C. Zoo
D. Sacred grove
Answer: C
Solution: Zoo = ex-situ (outside natural habitat).
Shortcut: “Zoo = animals on tour”.
Tag: Conservation strategiesThe chief source of ‘noise’ in pollution norms is measured in— A. ppm
B. decibels (dB)
C. mg/L
D. μg/m³
Answer: B
Solution: Loudness scale = decibels.
Tag: Noise pollutionEutrophication leads to— A. Increase in dissolved oxygen
B. Death of fish due to O₂ depletion
C. Reduction in algal biomass
D. Clear water
Answer: B
Solution: Excess nutrients → algal bloom → decomposition → anoxia.
Shortcut: “Troph” ≈ “Trophy algae, but fish lose”.
Tag: Water pollutionThe most potent greenhouse gas per molecule is— A. CO₂
B. CH₄
C. N₂O
D. SF₆
Answer: D
Solution: SF₆ has GWP 23 500 × CO₂.
Tag: Greenhouse gases‘Edge effect’ in ecology refers to— A. Soil erosion at forest borders
B. Increased diversity at habitat boundaries
C. Extinction of keystone species
D. Windthrow of trees
Answer: B
Solution: Junction of two habitats supports species from both + unique species.
Tag: Habitat ecology
Speed Tricks
| Situation | Shortcut | Example |
|---|---|---|
| Food chain length | Count arrows; ≤4 (energy loss 10 % rule) | Grass→Rabbit→Fox→Lion (3 arrows, 4 levels) |
| Ozone-friendly vs ODS | “4 C’s are bad” – CFC, Halon (starts with H but contains C), Carbon tetrachloride, Methyl chloroform | Replace with “4 H’s good” – HCFC, HFC, Hydrocarbons |
| Greenhouse gas GWP order | “C-M-N-S” ascending CO₂<CH₄<N₂O<SF₆ | SF₆ strongest |
| BOD value judgement | “5-17-50” rule: <5 = clean; 5-17 = light; >17 = heavy pollution | Recall 5 & 17 = railway platform numbers |
| In-situ vs Ex-situ | “IN the forest = IN-situ; OUT in cage = EX-situ” | Tiger Reserve vs Zoo |
Quick Revision
| Point | Detail |
|---|---|
| 1 | 10 % Energy Law → short trophic levels; apex predators least numerous. |
| 2 | Montreal → Ozone; Kyoto → GHG; Stockholm → Persistent Organic Pollutants; Ramsar → Wetlands. |
| 3 | Eutrophication sequence: N/P nutrients → algal bloom → O₂↓ → fish kill. |
| 4 | Biomagnification increases pollutant concentration at higher trophic levels (DDT, Hg). |
| 5 | NPP (Net Primary Productivity) highest in tropical rain-forests → earth’s ‘lungs’. |
| 6 | Carbon sequestration methods: afforestation, soil carbon, BECCS, blue carbon (mangroves). |
| 7 | National parks = no human interference; Wildlife sanctuaries = limited; Biosphere reserves = core + buffer + transition. |
| 8 | BOD measured in ppm (mg/L); safe drinking BOD <1 ppm. |
| 9 | Decibel scale logarithmic; 30 dB whisper, 90 dB train, >120 dB pain. |
| 10 | IUCN categories: Extinct → Critically Endangered → Endangered → Vulnerable → Near Threatened → Least Concern. |
BETA
