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
1. Which one is a sedimentary cycle?
A. Nitrogen cycle B. Carbon cycle C. Phosphorus cycle D. Water cycle **Answer:** C **Solution:** Phosphorus moves through rocks → soil → organisms → sediments; no gaseous phase. **Shortcut:** “P” for “Phosphorus” & “Particle (sediment)”. **Tag:** Biogeochemical cycles2. 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 flow3. Montreal 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 conventions4. Which 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 pollution5. BOD 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 quality6. The 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 development7. Which 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:** Biodiversity8. Minamata 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 diseases9. Kyoto 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 agreements10. The 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 web11. Which 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 strategies12. The 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 pollution13. Eutrophication 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 pollution14. The 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 gases15. ‘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 ecologySpeed 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
