🌿 Our Environment Class 10 Notes – Chapter 15 (Science) | CBSE 2025-26

🌿 Our Environment Class 10 Notes – Chapter 15 (Science) | CBSE 2025-26

Boost your CBSE Class 10 Science preparation with our easy-to-understand and exam-ready notes on Chapter 15: Our Environment. Specially tailored for the 2025–26 academic session, these notes explain key topics like ecosystems, food chains, waste management, and ozone depletion with clear definitions, real-life examples, and important CBSE questions.

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📘 Chapter Overview

• Subject: Science (Biology)

• Class: 10

• Board: CBSE & State Boards

• Chapter No.: 15

• Chapter Name: Our Environment

• Type: NCERT Notes, NCERT Solutions, PYQs

• Session: 2025–26

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📚 Table of Contents

1. What is an Ecosystem?

2. Types of Ecosystems

3. Self-sustainable Artificial Aquatic Ecosystem

4. Role of Decomposers

5. Food Chains and Food Webs

6. 10% Law of Energy Flow

7. Biological Magnification

8. Environmental Impact of Human Activities

9. Ozone Layer & Its Depletion

10. Waste Management – Biodegradable vs Non-Biodegradable

11. Eco-Friendly Practices

12. NCERT Solutions – Intext & Exercise Questions

13. CBSE Previous Year Questions (1M, 2M, 3M)

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🌱 Key Concepts Explained

🧩 Ecosystem: Components & Examples

An ecosystem includes both biotic (living) and abiotic (non-living) components like plants, animals, soil, air, and water.

• Natural ecosystems: Forests, lakes

• Artificial ecosystems: Gardens, aquariums

💧 Creating a Self-sustainable Aquarium

Add aquatic plants, fish, oxygen pump, and decomposers to replicate a natural aquatic system that cleans itself and maintains balance.

🔄 Role of Decomposers

• Recycle nutrients into soil

• Break down waste

• Maintain environmental cleanliness

• Balance nutrient flow

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🔗 Food Chain vs Food Web

Food Chain	Food Web
Linear path	Interconnected chains
One feeding line	Multiple feeding options
Less resilient	More resilient to disturbances

Example:

• Food Chain: Grass → Grasshopper → Frog → Snake → Hawk

• Food Web: Snake may also eat rats, frogs, beetles; hawk may eat several animals

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⚡ Energy Flow in Ecosystem – 10% Law

• Only 10% of energy is transferred to the next trophic level

• Energy transfer is unidirectional

• Example: Plants capture Sun’s energy → Herbivores → Carnivores

• Limits food chains to 3–4 levels

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🧪 Biological Magnification

The concentration of harmful chemicals (like DDT) increases at each trophic level. Top-level consumers (like humans) suffer the most due to maximum accumulation.

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🌍 Human Impact on Environment

• Ozone Layer shields us from harmful UV rays

• Depletion caused by CFCs in refrigerants and sprays

• Protection via international agreements (e.g., Montreal Protocol)

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🗑️ Waste Management

Biodegradable	Non-Biodegradable
Decomposes naturally	Persists in nature
e.g. Paper, food waste	e.g. Plastic, DDT

Eco-friendly habits:

• Use jute/paper bags

• Composting

• Walking/cycling

• Recycling and reducing usage

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📘 NCERT Solutions – Chapter 15: Our Environment

✅ Intext Questions & Answers (Page 257–258)

Q. What are trophic levels?
→ Steps in a food chain where energy is transferred.
Example:

• Producer: Grass

• Primary Consumer: Grasshopper

• Secondary Consumer: Frog

• Tertiary: Snake

• Quaternary: Hawk

Q. Why is ozone important?
→ Blocks UV radiation, protects life on Earth.

Q. How can we reduce waste?
→ Segregate biodegradable/non-biodegradable, recycle, reuse.

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📘 CBSE Previous Year Questions (PYQs)

🔹 1-Mark

• What are biodegradable substances? (CBSE 2020)

• Cause of ozone depletion? (CBSE 2017)

🔹 2-Marks

• What is biological magnification? (CBSE 2019)

• Two differences between biodegradable & non-biodegradable? (CBSE 2017)

🔹 3-Marks

• Explain 10% law of energy flow (CBSE 2018)

• Why ozone depletion is dangerous? (CBSE 2021)

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🧠 High-Scoring Topics to Revise

Topic	Marks	Frequency
Food chains & trophic levels	1–3M	Very High
Energy flow & 10% law	2–3M	High
Biological magnification	2–3M	Medium
Ozone layer depletion	1–2M	High
Waste management	1–3M	Medium

HastTags:

#Class10Science, #OurEnvironment, #Ecosystem, #FoodChain, #CBSE2025, #NCERTBiology, #EnvironmentAwareness, #ScienceNotes, #BiologicalMagnification, #10PercentLaw.

🏷️ Tags & SEO Keywords

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