Overview
Ecology studies the relationships between living organisms and their environment. This is one of the highest-scoring science topics in TNPSC Group 4, with 3–5 questions typically from environment, pollution, and biodiversity. Tamil Nadu has significant biodiversity and is frequently referenced.
Ecology — Basic Concepts
Levels of Organisation
| Term | Definition |
|---|---|
| Organism | Individual living being |
| Population | Group of same species in an area |
| Community | All populations in an area |
| Ecosystem | Community + abiotic environment |
| Biome | Large geographic area with similar climate and organisms (e.g., tropical rainforest, desert, tundra) |
| Biosphere | All ecosystems on Earth — zone of life |
Components of an Ecosystem
| Component | Type | Examples |
|---|---|---|
| Producers | Biotic (autotrophs) | Green plants, algae |
| Consumers | Biotic (heterotrophs) | Herbivores, carnivores, omnivores |
| Decomposers | Biotic | Bacteria, fungi |
| Abiotic factors | Non-living | Sunlight, water, soil, temperature, air |
Food Chain and Food Web
Food Chain
Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers
Example (Forest): Grass → Deer → Tiger
Example (Pond): Algae → Small Fish → Large Fish → Heron
Trophic Levels and Energy Flow
- Energy flows upward through trophic levels
- 10% Law (Lindemann, 1942) — only 10% of energy transfers from one trophic level to the next; 90% is lost as heat
- This is why food chains rarely have more than 4–5 levels
| Trophic Level | Organism | Energy Available |
|---|---|---|
| 1st (Producers) | Plants | 1000 kcal |
| 2nd (Herbivores) | Deer | 100 kcal |
| 3rd (Carnivores) | Fox | 10 kcal |
| 4th (Top Predator) | Eagle | 1 kcal |
Ecological Pyramids
- Pyramid of Numbers — number of organisms at each level
- Pyramid of Biomass — total mass of organisms at each level
- Pyramid of Energy — always upright (energy always decreases upward)
Biodiversity
India's Biodiversity
India has ~8% of world's species but only 2.4% of land area.
| Category | India's Share |
|---|---|
| Flowering plants | ~6% of world's species |
| Mammals | ~7.6% |
| Birds | ~12.5% |
| Reptiles | ~6.2% |
| Amphibians | ~4.4% |
Biodiversity Hotspots in India
A hotspot = area with exceptional biodiversity + high threat level (must have lost 70%+ original habitat)
| Hotspot | Location | Known For |
|---|---|---|
| Western Ghats | Kerala, TN, Karnataka, Maharashtra | Lion-tailed macaque, Nilgiri tahr, Malabar civet |
| Eastern Himalayas | Northeast India | Red panda, snow leopard |
| Andaman and Nicobar Islands | Bay of Bengal | Saltwater crocodile, Nicobar megapode |
TNPSC Tip: India has 4 biodiversity hotspots total — Western Ghats + Sri Lanka, Eastern Himalayas, Indo-Burma, and Sundaland (Andaman).
Protected Areas in India
| Category | Description | Example |
|---|---|---|
| National Park | No human activity; highest protection | Jim Corbett, Mudumalai (TN) |
| Wildlife Sanctuary | Some human activities permitted | Anamalai (TN), Guindy (Chennai) |
| Biosphere Reserve | Large area; core + buffer zone | Nilgiris (TN), Gulf of Mannar |
| Tiger Reserve | Under Project Tiger | Anamalai Tiger Reserve (TN) |
Tamil Nadu important sites:
- Mudumalai National Park (elephants, tigers, leopards)
- Gulf of Mannar Marine National Park (coral reefs, dugong)
- Guindy National Park (Chennai — smallest national park in India)
- Kalakkad Mundanthurai Tiger Reserve
Types of Pollution
Air Pollution
| Pollutant | Source | Effect |
|---|---|---|
| CO₂ | Fossil fuels, deforestation | Greenhouse effect, global warming |
| SO₂ | Coal burning, factories | Acid rain |
| NOₓ | Vehicle exhaust | Acid rain, smog |
| CO | Incomplete combustion | Toxic — binds haemoglobin |
| Particulate Matter (PM 2.5/10) | Dust, smoke | Respiratory diseases |
| CFCs | Refrigerants, aerosols | Ozone layer depletion |
Acid Rain
- Caused by SO₂ and NOₓ mixing with water vapour → forms H₂SO₄ and HNO₃
- Damages forests, lakes, soil; corrodes buildings and monuments (Taj Mahal issue)
- pH < 5.6
Water Pollution
| Pollutant | Source | Effect |
|---|---|---|
| Industrial effluents | Factories | Heavy metal poisoning |
| Agricultural run-off | Fertilizers, pesticides | Eutrophication, algal bloom |
| Sewage | Untreated wastewater | Cholera, typhoid |
| Oil spills | Shipping accidents | Marine life death |
Eutrophication — excess nutrients cause algal bloom → oxygen depletion → death of aquatic life
Soil Pollution
- Causes: pesticides, industrial waste, plastic
- Biomagnification — concentration of toxins increases at higher trophic levels (e.g., DDT in eagles)
Noise Pollution
- Above 85 dB causes hearing damage
- Sources: traffic, construction, industrial machinery
Greenhouse Effect and Climate Change
Greenhouse Gases (GHGs)
| Gas | Major Source | Global Warming Potential |
|---|---|---|
| CO₂ | Fossil fuels, deforestation | 1 (baseline) |
| CH₄ (Methane) | Livestock, paddy fields, landfills | 25× CO₂ |
| N₂O | Agriculture, fertilizers | 298× CO₂ |
| CFCs | Refrigerants (banned) | Very high |
| Water vapour | Natural | Natural amplifier |
Effects of Global Warming
- Rising sea levels (glaciers melting)
- More frequent extreme weather events
- Coral bleaching
- Spread of tropical diseases to new regions
- Threat to India's coastal cities (Mumbai, Chennai)
Ozone Layer Depletion
- Ozone (O₃) in stratosphere absorbs UV-B radiation
- CFCs (from old refrigerants, aerosols) break down ozone
- Montreal Protocol (1987) — international agreement to phase out CFCs
- Ozone hole discovered over Antarctica
Important Environmental Laws and Agreements
| Law / Agreement | Year | Purpose |
|---|---|---|
| Wildlife Protection Act | 1972 | Protects wild animals and plants |
| Forest Conservation Act | 1980 | Restricts deforestation |
| Environment Protection Act | 1986 | Framework for environmental protection |
| Water Act | 1974 | Controls water pollution |
| Air Act | 1981 | Controls air pollution |
| Montreal Protocol | 1987 | Phase out ozone-depleting substances |
| Kyoto Protocol | 1997 | Reduce greenhouse gas emissions (developed countries) |
| Paris Agreement | 2015 | Limit global warming to 1.5–2°C above pre-industrial levels |
National Bodies
- MoEFCC — Ministry of Environment, Forest and Climate Change
- CPCB — Central Pollution Control Board
- TNPCB — Tamil Nadu Pollution Control Board
Waste Management
| Waste Type | Method | Example |
|---|---|---|
| Biodegradable | Composting, biogas | Food waste, paper |
| Non-biodegradable | Recycling, incineration | Plastic, glass, metal |
| Hazardous | Special disposal | Batteries, chemicals |
| E-waste | Authorised recyclers | Old electronics |
3R Principle — Reduce, Reuse, Recycle
Previous Year TNPSC Questions (Pattern)
1. Q: The 10% law of energy transfer was proposed by → Lindemann 2. Q: Acid rain is caused by → SO₂ and NOₓ 3. Q: Which gas is responsible for ozone layer depletion? → CFCs (Chlorofluorocarbons) 4. Q: Eutrophication is related to → Water pollution (excess nutrients) 5. Q: Guindy National Park is located in → Chennai 6. Q: Montreal Protocol is related to → Ozone layer protection 7. Q: Which is NOT a greenhouse gas? → Oxygen (O₂) 8. Q: Biomagnification means → Increase in concentration of pollutants at higher trophic levels