📑 Topics on this page (Jump to Topic):
📌 1. Ecosystem & Energy Flow
- The term "ecosystem" — A. G. Tansley (1935); "ecology" — Ernst Haeckel (1866). Ecosystem = biotic (producers, consumers, decomposers) + abiotic components.
- Food chain: grass → grasshopper → frog → snake → hawk. Producers are green plants; decomposers — bacteria and fungi (recycle nutrients).
- Energy flow is unidirectional; Lindeman's 10% law — only about 10% of energy passes to the next trophic level. The ultimate energy source — the Sun.
- Biomagnification — concentration of non-biodegradable substances like DDT and mercury increases at higher trophic levels.
- Ecological pyramids: pyramid of numbers (can be inverted in a tree ecosystem), pyramid of energy always upright; pyramid of biomass can be inverted in aquatic ecosystems.
- Nitrogen cycle — atmospheric N₂ ~78%; fixed by Rhizobium, blue-green algae and lightning; denitrification — Pseudomonas. Carbon cycle — photosynthesis takes up CO₂, respiration and combustion return it.
📌 2. Pollution, Ozone & Climate Change
| Issue | Cause / fact |
|---|---|
| Ozone depletion | CFCs release chlorine that breaks O₃; the ozone layer in the stratosphere blocks UV-B; measured in Dobson units; ozone hole — over Antarctica |
| Greenhouse effect | CO₂, methane, N₂O, CFCs, water vapour — trap heat causing global warming |
| Acid rain | SO₂ and NOₓ; pH below 5.6; damages the Taj Mahal ("stone cancer") |
| Eutrophication | Excess nitrates-phosphates in water → algal bloom → dissolved O₂ falls |
| Bhopal gas tragedy (1984) | Methyl isocyanate (MIC) gas |
| Minamata disease / itai-itai | Mercury / cadmium poisoning (Japan) |
- The higher the BOD (biochemical oxygen demand), the more polluted the water. Sound intensity is measured in decibels (dB).
- Montreal Protocol (1987) — ozone-depleting substances; Kyoto Protocol (1997) — greenhouse gases; Paris Agreement (2015) — warming "well below" 2°C, pursuing 1.5°C. World Environment Day — 5 June; Ozone Day — 16 September.
📌 3. Biodiversity & Conservation
- The term "biodiversity" was popularised by E. O. Wilson. Biodiversity hotspots (Norman Myers) — 4 in India: Himalaya, Western Ghats-Sri Lanka, Indo-Burma, Sundaland (Nicobar).
- In-situ conservation — national parks, wildlife sanctuaries, biosphere reserves; ex-situ — zoos, botanical gardens, seed banks, gene banks.
- IUCN Red Data Book — list of threatened species. India: Project Tiger (1973), Project Elephant (1992), Wildlife (Protection) Act 1972, Environment (Protection) Act 1986.
- Chipko movement (1973, Uttarakhand) — Sunderlal Bahuguna, Chandi Prasad Bhatt; Appiko movement — Karnataka.
⚠️ Exam Traps:
- The pyramid of energy is never inverted.
- The ozone layer is in the stratosphere, not troposphere.
- Montreal — ozone; Kyoto — greenhouse gases.
📌 4. Practice MCQs
📝 Practice MCQs (prepared by SF Prep — not PYQs)
Q1. The term "ecosystem" was coined by: Practice
Correct answer: (A)
In 1935; "ecology" — Haeckel.
In 1935; "ecology" — Haeckel.
Q2. Energy flow in an ecosystem is: Practice
Correct answer: (A)
Sun → producers → consumers.
Sun → producers → consumers.
Q3. The 10% law of energy transfer was given by: Practice
Correct answer: (D)
In 1942.
In 1942.
Q4. Producers in a food chain are: Practice
Correct answer: (B)
Make food by photosynthesis.
Make food by photosynthesis.
Q5. Decomposers in an ecosystem are: Practice
Correct answer: (C)
Recycle nutrients.
Recycle nutrients.
Q6. Which ecological pyramid is always upright? Practice
Correct answer: (B)
Energy decreases at each level.
Energy decreases at each level.
Q7. Increasing DDT concentration at higher trophic levels is: Practice
Correct answer: (D)
Non-biodegradable substances accumulate.
Non-biodegradable substances accumulate.
Q8. The main cause of ozone layer depletion is: Practice
Correct answer: (B)
Chlorine atoms break O₃.
Chlorine atoms break O₃.
Q9. The ozone layer lies in the: Practice
Correct answer: (C)
Blocks UV rays.
Blocks UV rays.
Q10. The unit for measuring ozone is the: Practice
Correct answer: (B)
Decibel — sound.
Decibel — sound.
Q11. Gases responsible for acid rain are: Practice
Correct answer: (D)
Form sulphuric and nitric acids.
Form sulphuric and nitric acids.
Q12. The gas leaked in the Bhopal tragedy was: Practice
Correct answer: (D)
2–3 December 1984.
2–3 December 1984.
Q13. Minamata disease is caused by poisoning of: Practice
Correct answer: (C)
Itai-itai — cadmium.
Itai-itai — cadmium.
Q14. High BOD in water indicates: Practice
Correct answer: (A)
More organic waste.
More organic waste.
Q15. The treaty on ozone-depleting substances is the: Practice
Correct answer: (B)
1987; Kyoto — greenhouse gases.
1987; Kyoto — greenhouse gases.
Q16. World Environment Day is observed on: Practice
Correct answer: (D)
22 April — Earth Day.
22 April — Earth Day.
Q17. The Chipko movement is associated with: Practice
Correct answer: (A)
1973, Uttarakhand.
1973, Uttarakhand.
Q18. Which is ex-situ conservation? Practice
Correct answer: (C)
The other three are in-situ.
The other three are in-situ.
Q19. When was Project Tiger launched in India? Practice
Correct answer: (C)
Project Elephant — 1992.
Project Elephant — 1992.
Q20. How many biodiversity hotspots does India have (fully/partly)? Practice
Correct answer: (A)
Himalaya, Western Ghats, Indo-Burma, Sundaland.
Himalaya, Western Ghats, Indo-Burma, Sundaland.