Chapter: Our Environment

Class 10 Science – Comprehensive Notes

Introduction 

The environment is the sum of all external conditions influencing the life of organisms. It includes biotic (living) and abiotic (non-living) components, both of which interact to sustain life. Human activities such as industrialization, deforestation, and pollution have disrupted natural processes, leading to environmental issues like climate change and biodiversity loss. Understanding our environment helps in maintaining ecological balance and developing sustainable solutions. This chapter explores ecosystems, food chains, waste management, and the impact of human actions on nature.

Key Terms of the Chapter

1. Environment – The surroundings in which organisms live, including biotic and abiotic factors.
2. Ecosystem – A community of living organisms interacting with non-living elements in a specific area.
3. Food Chain – A linear sequence of organisms through which nutrients and energy pass.
4. Food Web – A network of interconnected food chains.
5. Trophic Levels – Different levels in a food chain representing energy flow.
6. Biodegradable Waste – Organic waste that decomposes naturally, e.g., vegetable peels.
7. Non-biodegradable Waste – Waste that does not break down easily, e.g., plastic.
8. Ozone Layer – A protective layer in the stratosphere that absorbs UV radiation.
9. Biomagnification – The accumulation of harmful substances at higher trophic levels.
10. Decomposers – Organisms like bacteria and fungi that break down organic matter.

Ecosystem – Components and Functioning 

An ecosystem consists of all living organisms (biotic factors) and non-living components (abiotic factors) in a specific area. The biotic components include producers (plants), consumers (animals), and decomposers (bacteria and fungi), while abiotic components include sunlight, air, water, soil, and temperature.

Ecosystems function through energy flow and nutrient cycling. Producers utilize solar energy to prepare food, which is passed through different trophic levels. Decomposers break down dead matter, recycling nutrients back into the environment. Natural ecosystems like forests, lakes, and grasslands maintain balance, while human-made ecosystems like agricultural fields and aquariums require human intervention for maintenance.

Examples:

• A forest ecosystem includes trees, animals, and microorganisms interacting with soil and climate.
• A pond ecosystem consists of algae, fish, and insects, depending on water and sunlight.

Food Chains and Food Webs 

A food chain represents the direct transfer of energy from one organism to another. It always begins with producers (plants), followed by primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers.

Example of a food chain:
Grass → Grasshopper → Frog → Snake → Eagle

A food web is a complex network of interconnected food chains in an ecosystem. It ensures stability by offering alternative food sources. Disrupting one species in a food web can affect multiple organisms.

Example of a food web:

• A rabbit and grasshopper both eat grass.
• A snake can eat a frog or a mouse.
• An eagle can eat a snake or a rabbit.

Table: Difference Between Food Chain and Food Web

Trophic Levels and Energy Flow 

The trophic level refers to the position an organism occupies in a food chain.

1. Producers (First Trophic Level): Plants convert solar energy into food through photosynthesis.
2. Primary Consumers (Second Trophic Level): Herbivores like cows and deer eat plants.
3. Secondary Consumers (Third Trophic Level): Carnivores like foxes and frogs consume herbivores.
4. Tertiary Consumers (Fourth Trophic Level): Top predators like eagles and lions feed on secondary consumers.

Energy flow follows the 10% Law, meaning only 10% of energy is transferred to the next level, while 90% is lost as heat. This limits the number of trophic levels in a food chain.

Example:
Sun → Grass (1000 kcal) → Deer (100 kcal) → Tiger (10 kcal)

Biodegradable and Non-biodegradable Substance 

Waste materials can be classified as biodegradable and non-biodegradable based on their decomposition rate.

Biodegradable Waste:

• Easily decomposed by microorganisms.
• Includes vegetable peels, paper, wood, and organic waste.
• Helps in nutrient recycling.

Non-biodegradable Waste:

• Does not break down easily.
• Includes plastic, glass, and synthetic chemicals.
• Causes long-term environmental damage like plastic pollution.

Table: Difference Between Biodegradable and Non-Biodegradable Waste

Ozone Layer and Its Depletion 

The ozone layer is a protective shield in the stratosphere that absorbs harmful ultraviolet (UV) radiation. It is composed of ozone (O₃) molecules formed by the reaction of oxygen with sunlight.

However, human activities have caused ozone depletion, mainly due to chlorofluorocarbons (CFCs) released from refrigerants, air conditioners, and aerosol sprays. A major consequence of ozone depletion is the ozone hole over Antarctica, leading to increased UV radiation, which can cause skin cancer, cataracts, and reduced crop productivity.

To combat this, international agreements like the Montreal Protocol (1987) were introduced to phase out CFCs. Today, alternatives like hydrofluorocarbons (HFCs) are being promoted to reduce ozone depletion.

Waste Management and Its Importance 

Proper waste management is crucial for maintaining a clean and sustainable environment. It involves:

1. Reduce: Minimizing waste production by using less plastic and conserving resources.
2. Reuse: Using materials multiple times, like cloth bags instead of plastic.
3. Recycle: Processing waste into reusable materials, e.g., paper recycling.

Effective waste management prevents land pollution, water contamination, and health hazards. Municipalities implement waste segregation into biodegradable and non-biodegradable categories to enhance disposal efficiency. Innovative solutions like composting, incineration, and waste-to-energy plants further reduce environmental impact.

Conclusion

Understanding and protecting our environment is essential for future generations. Ecosystems maintain a delicate balance, and human activities can either support or disrupt this balance. By adopting sustainable practices such as waste management, reducing pollution, and conserving biodiversity, we can contribute to a healthier planet. Awareness about the impact of non-biodegradable waste, ozone depletion, and energy conservation is vital for environmental protection. Small efforts at an individual level, such as reducing plastic use and promoting afforestation, can lead to significant positive changes in the ecosystem.

This comprehensive note ensures a structured and detailed understanding of the chapter “Our Environment”, covering all essential aspects with explanations, examples, and tables. It aligns with the latest NCERT syllabus, PYQs, and renowned sources, making it one of the best study materials available.