📘Class 10 Science – Chapter: Our Environment Notes
🌿 Introduction to Environment
Environment refers to the physical and biological conditions around us.
Includes both biotic components (plants, animals, microorganisms) and abiotic components (air, water, soil).
♻️ Ecosystem
🔹 Definition:
A system formed by the interaction of all living organisms with each other and with the physical and chemical factors of the environment in which they live.
🔹 Types of Ecosystems:
| Natural Ecosystems | Artificial Ecosystems |
|---|---|
| Forests, lakes, oceans | Crop fields, aquariums |
🔹 Components of Ecosystem:
| Biotic (Living) | Abiotic (Non-living) |
|---|---|
| Producers (plants) | Air, water, temperature |
| Consumers (animals) | Soil, light, minerals |
| Decomposers (bacteria) |
🌱 Food Chain and Food Web
🔹 Food Chain:
A series of organisms feeding on one another.
Always starts with producers (plants).
Example:
Grass → Grasshopper → Frog → Snake → Eagle
🔹 Trophic Levels:
Each step or level in the food chain.
| Trophic Level | Organism Type | Example |
|---|---|---|
| 1st | Producer | Plants |
| 2nd | Primary Consumer | Herbivores |
| 3rd | Secondary Consumer | Carnivores (Frog) |
| 4th | Tertiary Consumer | Top carnivores |
🔹 Food Web:
A network of interconnecting food chains.
More stable than food chains.
🔺 Energy Flow in Ecosystem
Energy flows in one direction: Sun → Producers → Consumers → Decomposers
Only 10% of energy is transferred to the next trophic level (10% Law by Lindeman).
Example:
If a plant gets 1000 J of energy from the sun,
Herbivore gets 100 J
Carnivore gets 10 J
Top carnivore gets 1 J
🦠 Decomposers
Microorganisms like bacteria and fungi that break down complex organic matter.
Return nutrients to the soil and clean the environment.
Functions:
Nutrient recycling
Decomposition of dead matter
Maintain balance in the ecosystem
🌏 Ozone Layer and Its Depletion
🔹 What is Ozone Layer?
A layer of O₃ molecules in the stratosphere.
Protects Earth from harmful UV rays.
🔹 Depletion Causes:
Use of CFCs (Chlorofluorocarbons) in refrigerants and aerosols.
Reaction Example (simplified):
CFCs → Cl· (free radical)
Cl· + O₃ → ClO + O₂
🔹 Harmful Effects:
Skin cancer
Eye damage (cataracts)
Damage to crops
🔹 Prevention:
Ban CFCs (as done in the Montreal Protocol)
Use of eco-friendly refrigerants
🗑️ Waste Management
🔹 Types of Waste:
| Type | Description | Example |
|---|---|---|
| Biodegradable | Can be broken down by microorganisms | Food waste, paper, cloth |
| Non-biodegradable | Cannot be decomposed easily | Plastics, metal, glass |
🔹 Problems of Non-Biodegradable Waste:
Pollution (air, water, soil)
Harmful to animals and humans
Accumulation in the environment
🔹 Management Practices:
Reduce, Reuse, Recycle
Composting biodegradable waste
Proper segregation and disposal
📊 Comparison: Biodegradable vs Non-biodegradable Waste
| Feature | Biodegradable | Non-biodegradable |
|---|---|---|
| Decomposition | Easily decomposed | Not easily decomposed |
| Environmental impact | Less harmful | More harmful |
| Examples | Kitchen waste, paper | Plastic bags, aluminium cans |
✅ Key Points to Remember
Energy flow is unidirectional.
Only 10% of energy is passed to next level.
Decomposers play a key role in nutrient recycling.
Ozone depletion is caused mainly by CFCs.
Waste should be managed using 3Rs: Reduce, Reuse, Recycle.