Environment and Ecology
Overview
This topic bridges science and current affairs, testing both conceptual understanding and awareness of contemporary environmental issues. The scope covers ecosystems and their functioning, India's rich biodiversity, the science and policy of climate change, and various forms of pollution with their control measures.
For TNPSC, focus on Indian-specific aspects — Western Ghats biodiversity, Nilgiri Biosphere Reserve, Tamil Nadu's environmental challenges, and national policies like the Environment Protection Act. Questions often link ecology concepts to real-world applications, so understanding the "why" behind conservation measures is crucial.
Key Concepts
- Ecosystem: A functional unit comprising living organisms (biotic) and non-living environment (abiotic) interacting through energy flow and nutrient cycling. Can be as small as a pond or as large as a biome.
- Food Chain vs Food Web: Food chain is a single linear pathway of energy transfer (grass → deer → tiger). Food web is an interconnected network of multiple food chains in an ecosystem — more realistic and stable.
- Ecological Pyramid: Graphical representation of trophic levels. Pyramid of energy is always upright (only 10% energy transfers to next level). Pyramid of biomass can be inverted in aquatic ecosystems.
- Biodiversity Hotspots: Regions with at least 1,500 endemic plant species and having lost 70% of original habitat. India has 4 hotspots — Western Ghats, Himalayas, Indo-Burma, and Sundaland (Nicobar Islands).
- Endemic vs Exotic Species: Endemic species are native and found only in a specific region (Lion-tailed macaque in Western Ghats). Exotic/alien species are introduced from outside (Lantana, water hyacinth) and can become invasive.
- Greenhouse Effect: Natural phenomenon where atmospheric gases (CO2, methane, water vapour) trap heat and warm Earth. Enhanced greenhouse effect due to human activities causes global warming.
- Biogeochemical Cycles: Circulation of essential elements (carbon, nitrogen, water) between biotic and abiotic components. Human interference disrupts these cycles — burning fossil fuels adds carbon, fertilizers add nitrogen.
- Ecological Succession: Gradual and predictable change in species composition over time. Primary succession starts on bare rock; secondary succession occurs after disturbance in existing ecosystem.
Key Facts
Biodiversity in India
- India is one of 17 megadiverse countries, hosting 7-8% of world's recorded species
- India has 4 of 36 global biodiversity hotspots
- Western Ghats — older than Himalayas, UNESCO World Heritage Site, 325+ endemic species
- Nilgiri Biosphere Reserve — India's first biosphere reserve (1986), part of UNESCO's MAB programme
Protected Areas in India
- National Parks: 106 (no human activity allowed) — Mudumalai, Gulf of Mannar in TN
- Wildlife Sanctuaries: 567 (limited human activity permitted)
- Biosphere Reserves: 18 (conservation + sustainable development)
- Tiger Reserves: 54 under Project Tiger (launched 1973)
Climate Change Facts
- Paris Agreement (2015): Limit warming to 1.5-2°C above pre-industrial levels
- India's NDC: 45% reduction in emission intensity by 2030; 50% energy from non-fossil sources
- India aims for Net Zero by 2070
Pollution Standards
- CPCB (Central Pollution Control Board) sets national standards
- AQI (Air Quality Index): 0-50 Good, 51-100 Satisfactory, 101-200 Moderate, 201-300 Poor, 301-400 Very Poor, 401-500 Severe
- BOD (Biochemical Oxygen Demand): Measures organic pollution in water; higher BOD = more polluted
- Bharat Stage VI norms: Current emission standard for vehicles (since April 2020)
Important Environmental Laws
- Wildlife Protection Act, 1972 — Schedules I-VI for species protection
- Environment Protection Act, 1986 — Umbrella legislation post-Bhopal disaster
- Forest Conservation Act, 1980 — Restricts diversion of forest land
- National Green Tribunal Act, 2010 — Dedicated environmental court
Worked Examples
Example 1: Trophic Level Problem In a grassland ecosystem, grass produces 10,000 J of energy. Calculate energy available to tertiary consumers.
Solution:
- 10% rule: Only 10% energy transfers to next trophic level
- Grass (Producers): 10,000 J
- Primary consumers (herbivores): 10,000 × 10% = 1,000 J
- Secondary consumers (carnivores): 1,000 × 10% = 100 J
- Tertiary consumers (top carnivores): 100 × 10% = 10 J
Example 2: Identifying Pollution Type A factory discharges hot water into a river. Fish population declines despite no chemical contamination. Identify the pollution type and cause.
Solution: This is thermal pollution. Hot water reduces dissolved oxygen levels in water (warm water holds less oxygen). Fish require adequate dissolved oxygen for respiration. The reduced oxygen causes fish mortality — a classic example of how physical changes, not just chemical pollutants, can harm ecosystems.
Example 3: Conservation Category Nilgiri Tahr is found only in the high ranges of Western Ghats. What conservation status applies?
Solution:
- Found only in one specific region → Endemic species
- IUCN Red List Status: Endangered
- Listed in Schedule I of Wildlife Protection Act (highest protection)
- Present in Eravikulam National Park (Kerala) and Mukurthi National Park (Tamil Nadu)
Common Mistakes
- Confusing weather and climate → Weather is short-term atmospheric condition; climate is average weather pattern over 30+ years. Climate change refers to long-term shifts, not daily temperature variations.
- Thinking all greenhouse gases are harmful → Natural greenhouse effect is essential for life (keeps Earth at habitable 15°C instead of -18°C). The problem is the enhanced greenhouse effect from excess emissions.
- Assuming national parks allow some human activity → National parks have strictest protection with no human habitation or resource extraction. Wildlife sanctuaries permit limited activities. Don't confuse their definitions.
- Mixing up conservation strategies → In-situ (on-site): National parks, sanctuaries, biosphere reserves. Ex-situ (off-site): Zoos, botanical gardens, seed banks, gene banks. TNPSC often tests this distinction.
- Forgetting local examples → Questions may specifically ask about Tamil Nadu. Remember: Gulf of Mannar Marine National Park, Point Calimere Wildlife Sanctuary, Anamalai Tiger Reserve, Vedanthangal Bird Sanctuary.
Quick Reference
- 10% Law: Only 10% of energy transfers between successive trophic levels
- India's Biodiversity Hotspots: Western Ghats, Himalayas, Indo-Burma, Sundaland (Nicobar)
- India's First Biosphere Reserve: Nilgiri (1986)
- AQI Severe Level: Above 400 — health emergency
- BOD indicates: Organic pollution in water (higher = worse)
- Paris Agreement Target: Limit global warming to 1.5°C above pre-industrial levels