NCERT Solutions for Class 10 Science Chapter 13: Our Environment

The chapter 'Our Environment' is a critical component of the CBSE Class 10 Science curriculum. While it is often considered one of the easiest chapters, it carries significant weightage in board exams because it tests your ability to connect biological concepts with real-world ecological issues. Understanding concepts like food chains, ozone depletion, and waste management is not just about passing exams; it is about building awareness of the world we inhabit. For a deeper dive into the theoretical aspects, you can review our full chapter notes to strengthen your core concepts before diving into these problems.

Understanding In-Text Questions

The NCERT textbook includes several thought-provoking questions that test your grasp of ecosystems and environmental management. Below are the step-by-step solutions to ensure you are well-prepared for your exams.

Why are some substances biodegradable and some non-biodegradable?

Answer: Substances are classified based on the ability of microorganisms (decomposers like bacteria and fungi) to break them down.

• Biodegradable: These are substances that can be broken down into simpler, harmless organic substances by biological processes. Examples include kitchen waste, paper, and wood.
• Non-biodegradable: These substances cannot be broken down by biological processes and persist in the environment for long periods. Examples include plastics, glass, and heavy metals.

Give any two ways in which biodegradable substances would affect the environment.

Answer:

1. Nutrient Recycling: Biodegradable waste acts as natural manure after decomposition, enriching the soil with nutrients.
2. Pest Breeding: If not disposed of properly, they may lead to the growth of harmful microorganisms and foul odors, acting as breeding grounds for flies and pests.

Exercise Questions and Step-by-Step Solutions

Mastering these NCERT solutions is the best way to ensure you can frame your answers effectively in the CBSE board papers. As per the official NCERT syllabus, these questions cover the fundamentals of environmental science.

Which of the following groups contain only biodegradable items?

(a) Grass, flowers, and leather (b) Grass, wood, and plastic (c) Fruit-peels, cake, and lime-juice (d) Cake, wood, and grass

Answer: (a), (c), and (d) are all correct. Option (b) is incorrect because plastic is non-biodegradable.

Which of the following constitute a food chain?

(a) Grass, wheat, and mango (b) Grass, goat, and human (c) Goat, cow, and elephant (d) Grass, fish, and goat

Answer: (b) Grass, goat, and human. A food chain represents the transfer of energy from producers to consumers.

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer: Biological magnification is the phenomenon where harmful, non-biodegradable chemicals (like pesticides) increase in concentration at each successive trophic level in a food chain.

• Difference in levels: Yes, the concentration is lowest in producers and highest in the top carnivores because these chemicals are not excreted and accumulate in fatty tissues. You can further explore CircleOfLearning to find more resources on how ecosystems function.

The Role of Ozone and Waste Management

One of the most frequently asked topics in this chapter is the formation and depletion of the ozone layer. Understanding this is essential for your practice tests and final board preparation.

What is the ozone layer and how does it get depleted?

Ozone (O3) is a molecule formed by three atoms of oxygen. It protects the Earth from harmful ultraviolet (UV) radiation from the sun. The depletion of the ozone layer is primarily caused by the release of Chlorofluorocarbons (CFCs), which are used in refrigerators and fire extinguishers.

How can you help in reducing the problem of waste disposal?

• Reduce: Minimize the use of single-use plastics.
• Reuse: Use containers and materials multiple times.
• Recycle: Process waste materials like paper and metal into new products.
• Composting: Separate organic waste for kitchen composting.

Tips to Score Full Marks in Board Exams

To excel in your Class 10 Science exam, follow these strategic tips:

1. Diagrams are Key: When answering questions about food chains or food webs, always draw a neat, labeled diagram. It helps the examiner understand your logic instantly.
2. Use Keywords: Use scientific terminology such as "trophic levels," "biological magnification," "producers," "consumers," and "biodegradable" to make your answers professional.
3. Point-wise Writing: CBSE evaluators prefer point-wise answers over long paragraphs. Use bullets to make your answer readable and concise.
4. Refer to Official Sources: Always align your preparation with guidelines from the official CBSE website to stay updated with any pattern changes.
5. Consistency: Don't wait until the last minute. Regularly browse all chapter notes to keep your knowledge fresh and ready for revision.

Frequently Asked Questions

Why is an ecosystem called a self-sustaining unit?

An ecosystem is self-sustaining because it involves the continuous interaction between biotic (living) and abiotic (non-living) components. The cycle of energy flow and nutrient recycling happens naturally without external intervention.

What is the difference between a food chain and a food web?

A food chain is a linear sequence of organisms where nutrients and energy are transferred from one to another. A food web is a complex network of interconnected food chains.

Why is energy flow in an ecosystem always unidirectional?

Energy flow is unidirectional because the energy captured by autotrophs (producers) does not revert back to the sun, and the energy lost as heat at each trophic level cannot be reused by the previous level.

How does the 10% law of energy transfer work?

According to the 10% law, only about 10% of the energy available at one trophic level is transferred to the next, while the remaining 90% is used for life processes and lost as heat.

Are there any career paths related to environmental studies?

Yes, environmental science is a growing field. Students interested in this subject can explore various scholarships & opportunities to pursue careers in environmental engineering, ecology, and sustainability management.

Summary

Class 10 Science Chapter 13 is an essential study for every student. By understanding how our actions affect the environment—from waste production to chemical accumulation—you become a more responsible citizen. Use these NCERT solutions as a baseline for your study, practice drawing food chains, and always emphasize the environmental impact of human choices.

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