🌿 Chapter 13: Our Environment

🎯 Class 10 Science Notes (Simple + Hindi Explanation)

♻️ 1. Ecosystem

An ecosystem is a system formed by the interaction of living organisms (biotic) with their non-living surroundings (abiotic).
Examples: Forest, pond, desert.

👉 Hindi: Jab jeevit aur ajeevit cheezein milkar ek system banati hain, use ecosystem kehte hain.

🧬 2. Components of Ecosystem

Biotic: Plants, animals, microorganisms
Abiotic: Air, water, soil, sunlight

🌱 3. Food Chain

A sequence of organisms where one is eaten by the next.
Example: Grass → Grasshopper → Frog → Snake → Eagle

👉 Hindi: Ek chain jisme ek jeev dusre ko khata hai, food chain kehlata hai.

🍴 4. Trophic Levels

Each step in a food chain is called a trophic level.

• 1st: Producers (plants)
  
  

• 2nd: Herbivores
  
  

• 3rd: Carnivores
  
  

• 4th: Top carnivores
  
  

Only 10% energy is passed to next level – rest is lost as heat (10% Law).

👉 Hindi: Food chain ke har step ko trophic level kehte hain. Har level par sirf 10% energy transfer hoti hai.

🔁 5. Food Web

Many interconnected food chains form a food web.

💥 6. Biological Magnification

Harmful chemicals (like DDT) increase in amount as we go up the food chain.
👉 Hindi: Zehreela padarth jaise DDT food chain mein upar jaake aur zyada ho jaata hai.

🚮 7. Waste Management

Biodegradable Waste:

• Gets decomposed by natural processes
  
  

• Example: Vegetable peels, paper
  
  

Non-Biodegradable Waste:

• Cannot be decomposed
  
  

• Example: Plastics, glass, metals
  
  

👉 Hindi: Kuch waste mitti mein mil jaata hai (biodegradable) aur kuch nahi milta (non-biodegradable).

🌍 8. Ozone Layer

• Ozone (O₃) protects Earth from harmful UV rays
  
  

• Depleted by CFCs (chlorofluorocarbons)
  
  

• Ozone layer protects life
  
  

👉 Hindi: Ozone suraj ke UV rays se humein bachata hai. CFC ise kharaab karta hai.

📘 Important Questions – With Answers

✅ 1 Mark Questions

1. What is an ecosystem?
   👉 A system where living and non-living things interact.
   
   

2. Name any non-biodegradable waste.
   👉 Plastic
   
   

✅ 2 Mark Questions

1. What is biological magnification?
   👉 The increase in concentration of harmful substances at each trophic level.
   
   

2. What is the 10% law?
   👉 Only 10% energy is transferred from one trophic level to the next.
   
   

✅ 3 Mark Questions

1. Explain the effects of ozone layer depletion.
   👉 More UV rays reach Earth, causing skin cancer, eye problems, and damage to plants and animals.
   
   

2. Draw a food chain with four trophic levels.
   👉 Example: Grass → Insect → Frog → Snake
   
   

✅ 5 Mark Questions

1. Describe the flow of energy in an ecosystem.
   
   

• Energy flows from Sun to producers to consumers.
  
  

• Only 10% energy passes to next level.
  
  

• Energy is lost as heat at each level.
  
  

2. Explain biodegradable and non-biodegradable substances with examples.
   | Biodegradable | Non-Biodegradable | |---------------|--------------------| | Easily decomposed | Do not decompose | | Paper, food waste | Plastic, metals |