Class 10 Science – Our Environment

Chapter 13: Our Environment

Introduction

The environment consists of all living and non-living components that interact with each other. Human activities have a significant impact on the environment, and understanding these effects is crucial for sustainable development.

Ecosystem – Structure and Function

A. What is an Ecosystem?

• An ecosystem is a self-sustaining unit where living organisms interact with each other and their physical environment.
• Examples: A pond, a forest, and a desert.

B. Components of an Ecosystem

1. Biotic Components (Living):
   • Producers (Plants, algae)
   • Consumers (Herbivores, carnivores, omnivores, decomposers)
   • Decomposers (Bacteria, fungi)
2. Abiotic Components (Non-living):
   • Air, water, soil, temperature, sunlight

Diagram: Structure of an Ecosystem

Food Chains and Food Webs

A. Food Chain

• A food chain is a linear sequence showing how energy flows through organisms.
• Example:
  • Grass → Grasshopper → Frog → Snake → Eagle

B. Food Web

• A food web is a complex network of interconnected food chains.
• It provides stability to the ecosystem.

C. Trophic Levels

• Each step in a food chain is called a trophic level.
• Example of Trophic Levels:
  1. Producers (1st level) – Plants
  2. Primary Consumers (2nd level) – Herbivores
  3. Secondary Consumers (3rd level) – Carnivores
  4. Tertiary Consumers (4th level) – Top predators

Diagram: Food Chain and Food Web

Energy Flow in an Ecosystem

• Energy follows a unidirectional flow in an ecosystem.
• 10% Law: Only 10% of energy is transferred from one trophic level to the next, while the rest is lost as heat.

Diagram: Energy Flow in a Food Chain

Biodegradable and Non-Biodegradable Substances

A. Biodegradable Substances

• Definition: Substances that can be broken down by natural decomposers.
• Examples: Paper, vegetable peels, dead plants and animals.

B. Non-Biodegradable Substances

• Definition: Substances that cannot be decomposed naturally.
• Examples: Plastic, glass, metals.
• Problems caused: Pollution, harm to wildlife, accumulation in the environment.

Diagram: Biodegradable vs. Non-Biodegradable Waste

Ozone Layer and Its Depletion

A. Importance of Ozone Layer

• The ozone layer (O₃) protects Earth from harmful ultraviolet (UV) rays of the Sun.

B. Causes of Ozone Depletion

• Use of chlorofluorocarbons (CFCs) in refrigerators, air conditioners, and aerosol sprays.

C. Effects of Ozone Layer Depletion

• Increased risk of skin cancer and cataracts.
• Harm to marine life and ecosystems.

D. Measures to Reduce Ozone Depletion

• Ban on CFCs (Montreal Protocol).
• Use of eco-friendly refrigerants.

Diagram: Ozone Layer and Its Depletion

Waste Management and Sustainable Development

A. Methods of Waste Disposal

1. Landfills – Large areas where waste is dumped.
2. Recycling – Processing waste into new products.
3. Composting – Organic waste converted into manure.
4. Incineration – Burning waste at high temperatures.

B. Importance of Sustainable Practices

• Reduce, Reuse, Recycle (3Rs).
• Avoid plastic usage.
• Promote eco-friendly products.

Diagram: 3Rs – Reduce, Reuse, Recycle