Class 10 Science – Chapter 15: Our Environment

 

🔷 Introduction

Our environment includes all living (biotic) and non-living (abiotic) things around us. It provides us with the resources we need to live – air, water, food, and shelter. But with the rise in pollution and human activity, the balance of the environment is getting disturbed.

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🔹 Components of the Environment

1. Biotic components – Living things like plants, animals, microorganisms.

2. Abiotic components – Non-living things like air, water, soil, sunlight.

These components form a system called an ecosystem.

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🌿 Ecosystem

An ecosystem is a self-contained unit of living and non-living things that interact with each other.

🔹 Examples of Ecosystems:

• Forest

• Pond

• Lake

• Grassland

• Desert

• Aquarium

🔹 Components of Ecosystem:

1. Producers – Green plants that prepare food by photosynthesis.

2. Consumers – Animals that consume plants or other animals:

   • Herbivores (eat plants)

   • Carnivores (eat animals)

   • Omnivores (eat both)

3. Decomposers – Microorganisms (like fungi and bacteria) that break down dead plants and animals into nutrients.

✅ Decomposers are very important because they recycle nutrients into the soil.

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🔁 Food Chains and Food Webs

🔹 Food Chain

A sequence showing who eats whom in an ecosystem.

Example:
Grass → Grasshopper → Frog → Snake → Eagle

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

🔹 Trophic Levels:

1. First trophic level: Producers (plants)

2. Second trophic level: Herbivores

3. Third trophic level: Carnivores

4. Fourth trophic level: Top carnivores

Only 10% of energy is transferred from one trophic level to the next. This is called the 10% Law (rest is lost as heat).

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🔹 Food Web

A network of interconnected food chains in an ecosystem. It shows how one organism may have many food sources or predators.

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🧪 Energy Flow in an Ecosystem

• Energy flows from sun → producers → consumers → decomposers.

• The flow of energy is unidirectional (one-way).

• Energy decreases as we move up the food chain due to the 10% law.

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🛑 Human Impact on the Environment

Due to population growth and industrialization, humans are polluting the environment through:

1. Garbage and waste (plastics, metals, etc.)

2. Chemicals and fertilizers

3. Air, water, and soil pollution

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♻️ Waste Management

There are two main types of waste:

Non-biodegradable waste causes long-term pollution.

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🧴 Ozone Layer and Its Depletion

🔹 What is the Ozone Layer?

• A layer of ozone (O₃) gas in the upper atmosphere that protects us from the sun’s harmful ultraviolet (UV) rays.

🔹 Ozone Depletion:

• Caused by chemicals called CFCs (chlorofluorocarbons) used in refrigerators, air conditioners, and sprays.

• Depletion leads to skin cancer, eye damage, and harm to plants and animals.

✅ To protect the ozone layer, the use of CFCs has been reduced worldwide under international agreements like the Montreal Protocol.

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✅ Conclusion

• Our environment is a delicate balance of living and non-living things.

• Human activities are harming this balance through pollution and waste.

• We must reduce, reuse, recycle, and avoid harmful chemicals to protect our environment for future generations.