Ecology & Environment Revision Notes (NEET)

Population Ecology

• Growth: exponential $dN/dt = rN$; logistic $dN/dt = rN(K-N)/K$.
• Age pyramid: expanding (broad base), stable, declining.
• Interactions: mutualism (+/+), competition (−/−), predation (+/−), commensalism (+/0), parasitism (+/−), amensalism (−/0).
• Gause's principle: no two species with same niche can coexist indefinitely.

Community Ecology

• Species diversity: richness + evenness.
• Simpson's index, Shannon-Weiner. Latitudinal gradient: tropics more diverse.
• Rivet vs redundancy hypothesis; Sp. Area relation $S = CA^Z$; Z = 0.6–1.2 for large scales.

Ecosystem

• Trophic levels: producers → primary consumers → secondary → tertiary → decomposers.
• 10% law of energy flow (Lindeman).
• GPP, NPP, secondary productivity.
• Pyramids of number, biomass, energy (always upright).
• Nutrient cycles: gaseous (C, N, O) and sedimentary (P, S).

Succession

• Primary (bare rock, pioneer = lichen) → xerarch.
• Secondary (after disturbance) → faster because soil exists.
• Hydrarch: pond → forest.

Biosphere & Biomes

• Tropical rainforest highest productivity; deserts lowest.
• Biodiversity hotspots: 4 in India — Western Ghats, Himalayas, Indo-Burma, Sundaland.

Environmental Issues

• Ozone hole: CFCs → Cl atoms destroy O₃ (Antarctic).
• Greenhouse: CO₂ (60%), CH₄ (20%), N₂O, CFCs.
• Eutrophication: nutrient loading → algal bloom → O₂ crash.
• Acid rain: SO₂/NOₓ → H₂SO₄/HNO₃, pH < 5.6.
• BOD ↑ indicates ↑ organic pollution.

Conservation

• In-situ: national park, biosphere reserve, sanctuary.
• Ex-situ: zoo, seed bank, botanical garden.
• Ramsar Convention (wetlands), CITES (trade in endangered), CBD (Rio 1992).

Practice MCQs

Q1. Logistic growth equation is A) dN/dt=rN B) dN/dt=rN(K-N)/K C) dN/dt=K/N D) dN/dt=1-N/K

Q2. Ten percent law was given by A) Odum B) Lindeman C) Tansley D) Elton

Q3. Which pyramid is always upright? A) Number B) Biomass C) Energy D) All

Q4. Fastest growing biotic community shows A) Wide base pyramid B) Narrow base pyramid C) Bell-shaped D) Inverted

Q5. Which is NOT a biodiversity hotspot in India? A) Western Ghats B) Himalayas C) Sundarbans D) Indo-Burma

Q6. Which gas is primarily responsible for ozone depletion? A) CO₂ B) CH₄ C) CFC D) SO₂

Q7. BOD is measured in A) mg/L B) % C) J D) mol

Q8. Highest NPP is in A) Tropical rainforest B) Grassland C) Desert D) Tundra

Q9. Species-area relation exponent Z on regional scale is typically A) 0.1–0.2 B) 0.6–1.2 C) 1.5–2.0 D) 0.001

Q10. Which is an example of mutualism? A) Cuckoo B) Lichen C) Sea anemone-clown fish D) Both B and C

Answers: 1-B (Verhulst-Pearl model.), 2-B (Lindeman 1942.), 3-C (Energy always decreases upward.), 4-A (Broad base = many young individuals.), 5-C (Sundarbans is a Ramsar site but not one of 4 hotspots.), 6-C (Cl radicals from CFCs.), 7-A (mg O₂ / L over 5 days.), 8-A (Warm & wet → high NPP.), 9-B (Continental scales Z between 0.6-1.2.), 10-D (Lichen (fungus+alga) and anemone-clown fish both.)

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