Chapter 13 – Our Environment (Class 10 Science, NCERT) – Notes

Chapter 13 – Our Environment (Class 10 Science, NCERT) – Notes

🌍 What is the Environment?

The environment is everything around us — air, water, land, animals, plants, and even tiny insects! It includes:

• 🌿 Living things (plants, animals, humans)
• 🪨 Non-living things (sunlight, air, water, soil)

Together, these form an ecosystem.

🧪 13.1 – Ecosystem: What’s in It?

👉 An ecosystem is a community where living things (plants, animals, microorganisms) interact with each other and with non-living things (air, water, soil, sunlight) in a specific area.

Examples:

• 🌳 A forest
• 🐟 A pond
• 🐠 An aquarium

🧑‍🤝‍🧑 Living Things (Biotic)

👉 The living parts of an ecosystem like plants, animals, and microorganisms are called biotic components.

• 🪴 Producers: Green plants — they make their own food using sunlight.
• 🐰 Consumers: Animals & humans — they eat plants or other animals.
• 🍄 Decomposers: Bacteria & fungi — they clean nature by breaking dead plants & animals.

🌞 Non-living Things (Abiotic)

👉 The non-living parts of an ecosystem like sunlight, air, water, temperature, and soil are called abiotic components.

• Sunlight ☀️
• Water 💧
• Soil 🪨
• Air 🌬️
• Temperature 🌡️

These things help living things survive!

🔗 13.1.1 – Food Chain & Food Web

🔗 What is a Food Chain?

👉 A food chain is a sequence that shows how energy and food move from one organism to another in an ecosystem.

Example:
🌿 Grass → 🐐 Goat → 🦁 Lion

Each step is called a Trophic Level:

1. 🌿 Producer (plants)
2. 🐰 Herbivore (plant eater)
3. 🐍 Carnivore (animal eater)
4. 🦅 Top carnivore

🧠 Only 10% energy passes to the next level. Rest is lost as heat.

🌐 What is a Food Web?

👉 A food web is a network of interconnected food chains where different organisms are linked with each other for food.
Example:
🦊 Fox eats 🐭 rats, 🐦 birds, and 🍇 fruits.
So, many food chains join to form a food web

⚠️ Biological Magnification

👉 The process by which harmful chemicals (like pesticides) increase in quantity at each higher level of the food chain is called biological magnification.

Some harmful chemicals (like DDT, plastics) stay in the food chain.
As we go higher, these chemicals become more dangerous!

🧪 Fish → 🐍 Snake → 🦅 Eagle → 👨 Human
Humans get the highest poison level. That’s why chemical use should be less.

🧑‍🔬 13.2 – How Do Humans Harm the Environment?

1. Ozone Layer Depletion

Ozone Layer

👉 The ozone layer is a protective layer of gas high up in the atmosphere that absorbs harmful ultraviolet (UV) rays from the sun.

Ozone Depletion

👉 The thinning or damaging of the ozone layer due to the release of harmful chemicals like CFCs (chlorofluorocarbons) is called ozone depletion.

• The ozone layer protects us from ☀️ harmful UV rays.
• But gases like CFCs (used in fridges, ACs, sprays) are destroying it.
• 🌤️ Less ozone = more UV rays = 😣 skin problems, eye damage, even cancer!

✅ Good News:
After global efforts (like banning CFCs), the ozone layer is recovering!

2. Biodegradable vs Non-Biodegradable Waste

Biodegradable Waste

👉 Substances that can be broken down naturally by microorganisms (like bacteria) are called biodegradable waste.

Examples: Vegetable peels, paper, cotton cloth.

Non-Biodegradable Waste

👉 Substances that cannot be broken down by natural processes and stay in the environment for a long time are called non-biodegradable waste.

Examples: Plastic, glass, synthetic cloth.

Type	What It Means	Examples
♻️ Biodegradable	Breaks down naturally	Food, leaves, paper
🚫 non-biodegradable	Stays for years	Plastic, glass, metal

🗑️ Plastic bags and bottles don’t rot. They pollute land and harm animals!

💡 Fun Activities in the Chapter

• 🌿 Make your own ecosystem in a bottle or aquarium!
• 🔍 Bury a banana peel and a plastic bag. After 1 week, see the difference — banana is gone, plastic is still there!

✅ Summary (Quick Revision)

Topic	Main Idea
🌍 Environment	Living + non-living things
🌱 Ecosystem	A natural system with interaction
🔗 Food Chain	One-way flow of energy
🌐 Food Web	Many food chains connected
♻️ 10% Law	Only 10% energy moves up each level
⚠️ Pollution	Human activities harm nature
🧪 Ozone Layer	Protects from UV rays
🚯 Waste	Plastic = non-biodegradable = danger!

🧠 Tips to Remember

• Food Chain = One path 🐄
• Food Web = Many paths 🕸️
• Ozone = Our Sun Shield ☂️
• Plastic = Nature’s Enemy 😠
• 10% Rule = Less energy as you go up 🔺