Ecology and Environment
Learn Ecology and Environment with notes, examples, and practice questions.
Chapter Overview
Ecosystems run on energy flow (one-way) and nutrient cycling (recycling) — two different stories.
Ecology studies interactions among organisms and with their environment. Population ecology, ecosystems, biodiversity, and conservation are central to environmental science and board exams.
Organisation Levels
- Individual → population → community → ecosystem → biome → biosphere
- Population: same species, same area, interbreeding
- Community: all populations in an area
Ecosystem Dynamics
Energy flow
10% law: ~10% energy transferred to next trophic level
Pyramids
Energy pyramid always upright; biomass/number may invert
GPP
Gross primary production; NPP = GPP − respiration
- Food chain: linear; food web: interconnected
- Decomposers recycle nutrients
- Ecological succession: primary (bare rock) vs secondary (after disturbance)
Biodiversity & Conservation
- Genetic, species, ecosystem diversity
- Hotspots: high endemism + threat (Western Ghats, Himalaya)
- In situ: national parks, sanctuaries; ex situ: zoos, gene banks
- Rio Convention, Cartagena Protocol — international frameworks
Pollution & Climate
- Eutrophication: excess nutrients → algal bloom → oxygen depletion
- Biomagnification: toxins accumulate up food chain (DDT, mercury)
- Ozone depletion: CFCs; greenhouse effect: CO₂, CH₄, global warming
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Example 1: 10% Law
Producers fix 10,000 J. Energy at secondary consumer level approximately?
- 1Primary consumer: ~1000 J
- 2Secondary consumer: ~100 J
Answer
~100 J
Example 2: Succession
Difference between primary and secondary succession.
- 1Primary: lifeless bare substrate (lava, rock); pioneer species like lichens.
- 2Secondary: soil already present after fire/flood; faster recovery.
Answer
Primary starts without soil; secondary has existing soil
Example 3: Biomagnification
Why is DDT highest in top carnivores?
- 1DDT is fat-soluble, not excreted easily.
- 2Accumulates at each trophic level — magnified at top.
Answer
Non-biodegradable toxin accumulates up food chain
Key Points to Remember
- ✓ Lindeman's 10% energy transfer rule
- ✓ Keystone species disproportionately affect ecosystem
- ✓ Carbon cycle, nitrogen cycle — know key reservoirs and processes
- ✓ India: 12% biodiversity hotspot share globally
Exam Tips
- • Draw pyramid of energy with values
- • Differentiate in situ vs ex situ with examples
- • Link pollution types to sources and effects
Formula Cheat Sheet
Quick reference — NCERT board exam formulas
Ecosystem & Energy
- 10% law (Lindeman):~10% energy transferred to next trophic level
- GPP:Gross primary production — total energy fixed by producers
- NPP:NPP = GPP − R (R = respiration)
- Energy pyramid: always upright (energy lost as heat at each level)
- Food chain: linear ; food web: interconnected chains
Biodiversity & Pollution
- Biomagnification:Fat-soluble toxins (DDT, Hg) increase concentration up food chain
- Eutrophication:Excess N, P → algal bloom → O₂ depletion → fish death
- In situ conservation: national parks, sanctuaries (natural habitat)
- Ex situ conservation: zoos, botanical gardens, gene banks
- Primary succession: bare rock/lava ; secondary: existing soil after disturbance
Practice MCQs — Ecology and Environment
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
10% law applies to: