Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Quick Summary
The biosphere is the zone of life on Earth where lithosphere, hydrosphere, and atmosphere interact. This chapter covers ecosystems, food chains, biomes, biodiversity, and the need for conservation.
Key Terms
| Term | Meaning |
|---|---|
| Ecosystem | Community of organisms + non-living environment |
| Biome | Large area with similar climate and life forms |
| Biodiversity | Variety of life forms on Earth |
| Food chain | Transfer of energy from one organism to another |
| Producer | Organism that makes its own food (plants) |
Ecosystems
Components
- Biotic (living): producers, consumers, decomposers
- Abiotic (non-living): water, soil, air, temperature, sunlight
Food Chain and Food Web
- Food chain: Plant → Grasshopper → Frog → Snake → Eagle
- Producers (plants) → Primary consumers (herbivores) → Secondary consumers → Tertiary consumers
- Food web: interlocking network of food chains
- Energy lost at each level (only 10% transferred upward)
Major Biomes of the World
| Biome | Climate | Vegetation | Location |
|---|---|---|---|
| Tropical Rainforest | Hot, very wet | Dense trees, vines | Amazon, Congo, Southeast Asia |
| Grassland (Savanna) | Hot, seasonal rain | Grasses, scattered trees | Africa, India (Deccan) |
| Desert | Hot/cold, dry | Cacti, sparse plants | Sahara, Thar, Atacama |
| Temperate Forest | Moderate | Oak, maple, beech | Europe, Eastern USA |
| Taiga (Boreal Forest) | Cold, moderate | Conifers (pine, fir) | Canada, Russia |
| Tundra | Very cold, dry | Mosses, lichens | Arctic regions |
India's Biodiversity
- India is one of 17 mega-diverse countries
- About 8% of world's known species found in India
- National parks and wildlife sanctuaries protect biodiversity
- Important ecosystems: Western Ghats, Eastern Himalayas, Sundarbans, Andaman Islands
- Western Ghats (including Tamil Nadu) is a biodiversity hotspot
Threats to the Biosphere
- Deforestation: habitat loss
- Pollution: air, water, soil pollution kills species
- Climate change: shifts biome boundaries
- Overexploitation: overfishing, overhunting
- Invasive species: non-native species outcompete native ones
Conservation
- Protected areas: National Parks, Wildlife Sanctuaries, Biosphere Reserves
- Biosphere reserves in Tamil Nadu: Nilgiri Biosphere Reserve, Gulf of Mannar
- Project Tiger, Project Elephant, Project Snow Leopard
- International agreements: CITES, Convention on Biological Diversity
Important Questions
One Mark
1. What is an ecosystem? 2. Name one major biome of the world. 3. What is a food chain? Give one example. 4. What is biodiversity? 5. Name one biosphere reserve in Tamil Nadu.
Short Answer (3 marks)
1. Explain the components of an ecosystem with examples. 2. What are biomes? Describe any two major biomes. 3. What are the main threats to biodiversity? Name three.
Long Answer (5 marks)
1. Explain the major biomes of the world with their characteristics. 2. Describe India's biodiversity and the measures taken to conserve it.
Common Mistakes
- Producers are plants (autotrophs), not animals.
- Only 10% of energy passes to the next level in a food chain — 90% is lost.
- Western Ghats is a BIODIVERSITY HOTSPOT — not just a forest area.
Revision Checklist
- I can draw and explain a food chain with 4 levels.
- I can describe 3 biomes with their climate and vegetation.
- I know 2 biosphere reserves in India, including one in Tamil Nadu.
- I can list 3 threats to biodiversity.