Environment and Ecology — TNPSC Group II/IIA Science
Overview
Environment and ecology is a frequently tested science topic in TNPSC Group 2/2A. Questions cover ecosystem concepts, biodiversity, pollution types and effects, environmental laws, and conservation measures — particularly relevant to Tamil Nadu's diverse ecosystems.
Ecology — Basic Concepts
Levels of Organisation
| Level | Description |
|---|---|
| Individual | Single organism |
| Population | All individuals of same species in an area |
| Community | All populations of different species in an area |
| Ecosystem | Community + Abiotic environment |
| Biome | Large geographic area with similar climate and communities |
| Biosphere | All ecosystems on Earth; zone of life |
Components of an Ecosystem
Biotic (Living) Components:
- Producers (Autotrophs): Plants, algae — make food through photosynthesis
- Consumers (Heterotrophs):
- Primary consumers: Herbivores (eat plants)
- Secondary consumers: Carnivores (eat herbivores)
- Tertiary consumers: Top carnivores
- Decomposers: Bacteria and fungi — break down dead matter; return nutrients to soil
Abiotic (Non-Living) Components:
- Light, temperature, water, soil, minerals, gases (CO₂, O₂)
Food Chain and Food Web
Food Chain
Linear sequence showing energy flow: Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers
Example: Grass → Grasshopper → Frog → Snake → Eagle
Food Web
- Multiple interconnected food chains
- More realistic; reflects nature's complexity
- Energy flows: 10% Rule — only 10% of energy transfers to next level
Energy Pyramids
| Pyramid | Description |
|---|---|
| Pyramid of Numbers | Number of organisms at each trophic level |
| Pyramid of Biomass | Total mass at each level |
| Pyramid of Energy | Energy at each level — always upright (never inverted) |
Trophic Levels
- Level 1: Producers (plants)
- Level 2: Primary consumers (herbivores)
- Level 3: Secondary consumers (carnivores)
- Level 4: Tertiary consumers (top carnivores)
- Each level has 10% of energy of previous level
Biogeochemical Cycles
| Cycle | Key Processes |
|---|---|
| Carbon Cycle | Photosynthesis, respiration, decomposition, fossil fuel burning |
| Nitrogen Cycle | Nitrogen fixation, nitrification, denitrification, ammonification |
| Water Cycle | Evaporation, condensation, precipitation, transpiration |
| Oxygen Cycle | Photosynthesis (produces O₂), respiration (uses O₂) |
Nitrogen fixation: Converting atmospheric N₂ to usable forms
- By Rhizobium bacteria (in root nodules of legumes)
- By Cyanobacteria (blue-green algae)
- By lightning
Biodiversity
Types of Biodiversity
- Genetic Diversity: Variation in genes within a species
- Species Diversity: Number and variety of species in an area
- Ecosystem Diversity: Variety of ecosystems in a region
India's Biodiversity
1. Western Ghats and Sri Lanka: Covers Western Ghats in Tamil Nadu, Kerala, Karnataka, Maharashtra 2. Indo-Burma: Northeast India, Myanmar, Thailand
- India is one of 17 Megadiverse countries in the world
- 8% of world's species; 45,000+ plant species; 90,000+ animal species
- 2 Biodiversity Hotspots:
IUCN Categories (International Union for Conservation of Nature)
| Category | Meaning |
|---|---|
| Extinct (EX) | No known living individuals |
| Extinct in Wild (EW) | Only in captivity |
| Critically Endangered (CR) | Extremely high risk of extinction |
| Endangered (EN) | High risk of extinction |
| Vulnerable (VU) | High risk if circumstances unchanged |
| Near Threatened (NT) | Close to qualifying for threatened |
| Least Concern (LC) | Widespread and abundant |
Environmental Issues
Air Pollution
| Pollutant | Source | Effect |
|---|---|---|
| CO₂ | Combustion | Greenhouse effect, climate change |
| SO₂ | Industries, power plants | Acid rain, respiratory problems |
| NO₂ | Vehicles, industries | Acid rain, smog |
| CO | Incomplete combustion | Poisonous; blocks haemoglobin |
| Particulate matter (PM2.5, PM10) | Dust, vehicles | Respiratory diseases |
| CFCs | Old refrigerators, ACs | Ozone layer depletion |
| Lead | Old petrol, paint | Neurotoxic |
Greenhouse Effect and Climate Change
- Greenhouse gases: CO₂, CH₄, N₂O, H₂O vapour, CFCs
- Trap heat in atmosphere → global warming
- Effects: Rising sea levels, extreme weather, melting ice caps
- Paris Agreement (2015): Limit global warming to 1.5°C above pre-industrial levels
Ozone Layer Depletion
- Ozone (O₃) layer in stratosphere protects from UV radiation
- CFCs (from refrigerants, aerosols) destroy ozone
- Montreal Protocol (1987): International treaty phasing out ozone-depleting substances
- Antarctic ozone hole: Discovered 1985
Water Pollution
- Sources: Industrial effluents, sewage, agricultural runoff, oil spills
- Effects: Kills aquatic life, spreads waterborne diseases, affects fisheries
- BOD (Biochemical Oxygen Demand): Measure of water pollution; higher BOD = more polluted
Soil Pollution
- Pesticides, fertilisers, plastic waste, industrial chemicals
- Bhopal Gas Tragedy (1984): MIC gas leak from Union Carbide plant; worst industrial accident in history
Conservation of Biodiversity
In-Situ Conservation (in natural habitat)
- Protected Areas: National Parks, Wildlife Sanctuaries, Biosphere Reserves
- Community Reserves, Conservation Reserves
Ex-Situ Conservation (outside natural habitat)
- Zoos, Botanical Gardens, Seed Banks
- Gene Bank: Seeds stored in cold; Svalbard Global Seed Vault (Norway)
Protected Area Network in India
| Type | Criteria | Example (Tamil Nadu) |
|---|---|---|
| National Park | Strictly protected; no human activities | Mudumalai NP, Guindy NP |
| Wildlife Sanctuary | Human activities allowed; species protection | Grizzled Giant Squirrel WLS |
| Biosphere Reserve | Conservation + sustainable use | Nilgiri Biosphere Reserve |
| Tiger Reserve | Tiger protection; Project Tiger | Mudumalai, Anamalai, Kalakkad, Sathyamangalam |
Project Tiger
- Launched: 1973 by PM Indira Gandhi
- Currently: 54 Tiger Reserves in India
- Tiger population: ~3000 (2022 census) — 75% increase since 2006
- Tamil Nadu Tiger Reserves: Mudumalai, Anamalai, Kalakkad-Mundanthurai, Sathyamangalam
Project Elephant
- Launched: 1992
- Protects elephant habitats; reduces human-elephant conflict
- 32 Elephant Reserves in India
Environmental Laws and Bodies in India
| Law/Body | Year | Purpose |
|---|---|---|
| Wildlife Protection Act | 1972 | Protection of wild plants and animals; schedules |
| Water Pollution Act | 1974 | Prevent and control water pollution |
| Forest Conservation Act | 1980 | Protect forests; restrict diversion |
| Air Pollution Act | 1981 | Prevent and control air pollution |
| Environment Protection Act | 1986 | Umbrella legislation; comprehensive |
| Biological Diversity Act | 2002 | Conservation and fair sharing of biodiversity |
| NGT (National Green Tribunal) | 2010 | Fast-track court for environmental cases |
| CPCB | 1974 | Central Pollution Control Board |
| TNPCB | — | Tamil Nadu Pollution Control Board |
Key Facts for TNPSC Group II/IIA
- Ecosystem: Biotic + Abiotic components interacting together
- 10% Energy Rule: Only 10% of energy transferred at each trophic level
- Biodiversity hotspots in India: Western Ghats + Sri Lanka; Indo-Burma (NE India)
- India is Megadiverse: 8% of world's species; 17 Megadiverse countries
- Nilgiri Biosphere Reserve: India's first (1986); TN, Karnataka, Kerala
- Project Tiger: 1973; 54 tiger reserves; ~3000 tigers in India
- CFCs: Destroy ozone layer; Montreal Protocol (1987) banning them
- Bhopal Gas Tragedy: 1984; MIC gas; worst industrial accident
- Wildlife Protection Act 1972: Four schedules; highest protection to Schedule I animals
- NGT (National Green Tribunal): Fast-track environmental court; established 2010
Previous Year MCQ Patterns
Q: The '10% energy rule' in ecology refers to: a) 10% of species are endangered b) Only 10% of energy passes to the next trophic level c) 10% of organisms die each year d) Plants use only 10% of sunlight
Q: Which of the following is India's first biosphere reserve? a) Sundarbans b) Gulf of Mannar c) Nilgiri d) Great Nicobar
Q: Project Tiger was launched in India in: a) 1969 b) 1973 c) 1980 d) 1992
Frequently Asked Questions
An ecosystem is a community of living organisms (biotic components) interacting with their non-living environment (abiotic components). Biotic components: Producers (plants), Consumers (animals), Decomposers (bacteria, fungi). Abiotic components: Air, water, soil, temperature, sunlight. Examples: Forest ecosystem, pond ecosystem, desert ecosystem, marine ecosystem.