🌟 Introduction

Our Environment is one of the most important chapters in the Class 10 CBSE Science syllabus. For students preparing for CBSE Board examinations, solving Previous Year Questions (PYQs) is the most effective way to understand the exam pattern, marking scheme, and frequently repeated themes. At Dhingra Classes Nashik, we have compiled the most important PYQs from this chapter, organized by marks weightage, to help Class 10 students score maximum marks.

This chapter covers Ecosystem, Food Chain, Food Web, Trophic Levels, Energy Flow, Biodegradable Waste, Non-Biodegradable Waste, Ozone Depletion, and Waste Management. These PYQs have been collected from CBSE Board exams across multiple years and are essential for effective board exam preparation.

📚 Why Solving PYQs Is Important for CBSE Class 10

Before diving into the questions, let us understand why Previous Year Questions are crucial for Class 10 CBSE students.

🎯 Benefits of Solving PYQs

• ✅ Understanding Exam Pattern: PYQs reveal how questions are framed

• 📝 Identifying Repeated Themes: Many questions repeat with slight variations

• 🧠 Better Answer Writing: PYQs help practice structured answers

• 🏆 Higher Scores: Familiarity with question types reduces exam stress

• 📊 Time Management: Practice helps allocate time per question correctly

• 🔬 Diagram Practice: Many PYQs require drawing food chains and webs

📖 1 Mark Questions (Very Short Answer Type)

These questions are typically asked as MCQs, Assertion-Reason, or one-line answers. They test factual knowledge and basic understanding.

Set A: MCQs and One-Line Answers

Set B: Assertion-Reason Questions

Question 1: Assertion (A): Energy flow in an ecosystem is unidirectional. Reason (R): Energy is lost as heat at each trophic level.
Answer: Both A and R are true and R is the correct explanation of A.

Question 2: Assertion (A): Ozone layer is essential for life on Earth. Reason (R): It absorbs harmful ultraviolet radiation from the sun.
Answer: Both A and R are true and R is the correct explanation of A.

📖 2 Marks Questions (Short Answer Type I)

These questions require two points or brief explanations and are designed to test conceptual understanding.

Question 1: Why is the ozone layer important for us?

Answer:

• The ozone layer absorbs harmful ultraviolet (UV) radiation from the sun.

• UV radiation can cause skin cancer, cataracts, and damage to crops in humans and other organisms.

Question 2: What is biological magnification? How does it affect humans?

Answer:

• Biological magnification is the increase in concentration of harmful chemicals at successive trophic levels.

• Humans, being at the top of the food chain, accumulate the highest concentration of these chemicals, causing health problems.

Question 3: What are the two types of waste based on decomposition? Give examples.

Answer:

• Biodegradable waste: Waste that can be decomposed by microorganisms, e.g., kitchen waste, paper.

• Non-biodegradable waste: Waste that cannot be decomposed, e.g., plastic, glass, DDT.

Question 4: Why do food chains generally consist of only 3 or 4 trophic levels?

Answer:

• Energy is lost as heat at each trophic level, so only about 10% of energy is transferred.

• After 3–4 levels, very little energy remains to support another trophic level.

Question 5: What is the role of decomposers in an ecosystem?

Answer:

• Decomposers break down dead plants and animals into simpler substances.

• They return nutrients to the soil, which are reused by producers.

Question 6: How is ozone formed in the atmosphere?

Answer:

• Ozone is formed when UV radiation splits oxygen molecules into free oxygen atoms.

• These atoms combine with molecular oxygen to form ozone (O₃).

Question 7: What is the significance of the food web?

Answer:

• A food web shows multiple feeding relationships in an ecosystem.

• It provides stability to the ecosystem, as organisms can feed on different sources.

Question 8: Why is plastic considered a major environmental hazard?

Answer:

• Plastic is non-biodegradable and persists in the environment for hundreds of years.

• It causes soil and water pollution and harms animals that consume it.

📖 3 Marks Questions (Short Answer Type II)

These questions require detailed explanations with three distinct points and test analytical understanding.

Question 1: Explain the flow of energy in an ecosystem with the help of a food chain.

Answer:

• Energy enters the ecosystem through producers (green plants) via photosynthesis.

• It passes to herbivores (primary consumers), then to carnivores (secondary consumers), and so on.

• At each trophic level, about 90% of energy is lost as heat, so only 10% is transferred to the next level.

Question 2: Explain the process of ozone depletion and its harmful effects.

Answer:

• Ozone depletion is caused by chlorofluorocarbons (CFCs) used in refrigerators and aerosols.

• CFCs release chlorine atoms that break down ozone molecules, thinning the ozone layer.

• This allows harmful UV radiation to reach the Earth, causing skin cancer, cataracts, and crop damage.

Question 3: What is biological magnification? Explain with an example.

Answer:

• Biological magnification is the increase in concentration of harmful chemicals at successive trophic levels.

• Example: DDT sprayed on crops enters the soil and water, is absorbed by plants, then by fish, and finally by birds.

• The highest concentration is found in humans and top carnivores, causing health problems.

Question 4: Explain the role of decomposers in the ecosystem.

Answer:

• Decomposers like bacteria and fungi break down dead plants and animals.

• They convert complex organic matter into simpler inorganic substances.

• These nutrients are returned to the soil and reused by producers, maintaining nutrient cycling.

Question 5: How can we manage waste effectively? Explain any three methods.

Answer:

• Reduce: Minimize the use of non-biodegradable materials like plastic.

• Reuse: Use items like containers and bags multiple times.

• Recycle: Process waste materials like paper, glass, and metal into new products.

Question 6: Explain the difference between biodegradable and non-biodegradable waste with examples.

Answer:

• Biodegradable waste can be decomposed by microorganisms, e.g., food waste, paper, cotton.

• Non-biodegradable waste cannot be decomposed, e.g., plastic, glass, metals, DDT.

• Biodegradable waste is eco-friendly, while non-biodegradable waste causes long-term pollution.

Question 7: What is a food web? How is it different from a food chain?

Answer:

• A food web is a network of interconnected food chains in an ecosystem.

• A food chain is a single linear sequence of energy transfer.

• Food webs provide more stability to the ecosystem than food chains.

Question 8: Explain the harmful effects of non-biodegradable waste on the environment.

Answer:

• Non-biodegradable waste like plastic persists in the environment for hundreds of years.

• It causes soil and water pollution and blocks drains, leading to flooding.

• Animals often consume plastic and die; it also enters the food chain, affecting humans.

Question 9: How does energy flow in an ecosystem? Explain the 10% law.

Answer:

• Energy flows from producers to consumers in a unidirectional manner.

• According to the 10% law, only about 10% of energy is transferred from one trophic level to the next.

• The remaining 90% is lost as heat during respiration and other metabolic activities.

Question 10: Explain the importance of the ozone layer and the steps to protect it.

Answer:

• The ozone layer absorbs harmful UV radiation from the sun, protecting life on Earth.

• It prevents skin cancer, cataracts, and damage to crops.

• Steps to protect it include banning CFCs, using eco-friendly refrigerants, and international agreements like the Montreal Protocol.

Question 11: What are the effects of ozone depletion on human health?

Answer:

• Ozone depletion allows harmful UV radiation to reach the Earth’s surface.

• It causes skin cancer, cataracts, and weakening of the immune system.

• It also leads to premature aging of skin and sunburn.

Question 12: Explain the role of producers, consumers, and decomposers in an ecosystem.

Answer:

• Producers: Make their own food through photosynthesis, e.g., green plants.

• Consumers: Depend on producers for food, e.g., herbivores and carnivores.

• Decomposers: Break down dead matter and return nutrients to the soil, e.g., bacteria and fungi.

📖 5 Marks Questions (Long Answer Type)

These questions require comprehensive answers with five distinct points and test in-depth understanding and analytical skills.

Question 1: Explain the structure and function of an ecosystem with examples.

Answer:

• An ecosystem is a self-contained unit of living organisms interacting with each other and their physical environment.

• Biotic components: Producers (green plants), consumers (herbivores, carnivores), and decomposers (bacteria, fungi).

• Abiotic components: Sunlight, water, air, soil, and temperature.

• Energy flow: Energy enters through producers and flows through trophic levels; only 10% is transferred at each level.

• Nutrient cycling: Decomposers return nutrients to the soil for reuse by producers.

Question 2: Explain the concept of biological magnification with an example.

Answer:

• Biological magnification is the increase in concentration of harmful chemicals at successive trophic levels.

• Example: DDT sprayed on crops enters the soil and water, is absorbed by plants, then by fish, and finally by birds.

• The highest concentration is found in humans and top carnivores.

• It causes health problems like cancer, reproductive disorders, and immune system damage.

• It shows how human activities can harm the entire ecosystem.

Question 3: Explain the process of ozone depletion and its harmful effects.

Answer:

• Ozone depletion is caused by chlorofluorocarbons (CFCs) used in refrigerators and aerosols.

• CFCs release chlorine atoms that break down ozone molecules, thinning the ozone layer.

• This allows harmful UV radiation to reach the Earth, causing skin cancer, cataracts, and crop damage.

• It also affects marine life and phytoplankton, disrupting the food chain.

• Steps to protect the ozone layer include banning CFCs and international agreements like the Montreal Protocol.

Question 4: Explain the different types of waste and methods of waste management.

Answer:

• Biodegradable waste: Can be decomposed by microorganisms, e.g., food waste, paper.

• Non-biodegradable waste: Cannot be decomposed, e.g., plastic, glass, metals.

• Waste management methods: Reduce, Reuse, Recycle (3Rs).

• Composting: Converting organic waste into manure.

• Incineration: Burning waste at high temperatures; landfills for disposing non-biodegradable waste.

Question 5: Explain the flow of energy in an ecosystem with the help of a food chain and food web.

Answer:

• Energy enters the ecosystem through producers (green plants) via photosynthesis.

• It passes to herbivores (primary consumers), then to carnivores (secondary consumers), and so on.

• At each trophic level, about 90% of energy is lost as heat, so only 10% is transferred.

• A food chain is a single linear sequence, while a food web is a network of interconnected food chains.

• Food webs provide more stability to the ecosystem.

Question 6: What is the importance of the ozone layer? How can we protect it?

Answer:

• The ozone layer absorbs harmful UV radiation from the sun, protecting life on Earth.

• It prevents skin cancer, cataracts, and damage to crops.

• Steps to protect it include banning CFCs, using eco-friendly refrigerants, and international agreements like the Montreal Protocol.

• Public awareness and government regulations are also essential.

• Protecting the ozone layer is crucial for human health and ecosystem stability.

Question 7: Explain the role of decomposers in the ecosystem and the consequences of their absence.

Answer:

• Decomposers like bacteria and fungi break down dead plants and animals.

• They convert complex organic matter into simpler inorganic substances.

• These nutrients are returned to the soil and reused by producers.

• In their absence, dead matter would accumulate, and nutrients would not be recycled.

• This would disrupt the entire ecosystem and lead to the collapse of life-support systems.

Question 8: How does biological magnification affect the food chain? Explain with an example.

Answer:

• Biological magnification is the increase in concentration of harmful chemicals at successive trophic levels.

• Example: DDT sprayed on crops enters the soil and water, is absorbed by plants, then by fish, and finally by birds.

• The highest concentration is found in humans and top carnivores.

• It causes health problems like cancer, reproductive disorders, and immune system damage.

• It shows how human activities can harm the entire ecosystem.

Question 9: Explain the different trophic levels in a food chain with examples.

Answer:

• First trophic level: Producers (green plants) that make their own food.

• Second trophic level: Primary consumers (herbivores) that eat producers, e.g., deer, rabbit.

• Third trophic level: Secondary consumers (carnivores) that eat herbivores, e.g., fox, snake.

• Fourth trophic level: Tertiary consumers (top carnivores) that eat other carnivores, e.g., lion, eagle.

• Decomposers break down dead matter at all levels and return nutrients to the soil.

Question 10: Explain the harmful effects of plastic on the environment and methods to reduce plastic pollution.

Answer:

• Plastic is non-biodegradable and persists in the environment for hundreds of years.

• It causes soil and water pollution and blocks drains, leading to flooding.

• Animals often consume plastic and die; it also enters the food chain, affecting humans.

• Methods to reduce plastic pollution include using cloth bags, recycling, and banning single-use plastic.

• Public awareness and government regulations are essential to tackle plastic pollution.

Question 11: Explain the importance of waste management and the 3Rs.

Answer:

• Waste management is essential to protect the environment and human health.

• The 3Rs are Reduce, Reuse, and Recycle.

• Reduce: Minimize the use of non-biodegradable materials like plastic.

• Reuse: Use items like containers and bags multiple times.

• Recycle: Process waste materials like paper, glass, and metal into new products.

Question 12: Explain the effects of human activities on the environment.

Answer:

• Deforestation: Cutting down forests leads to soil erosion and loss of biodiversity.

• Pollution: Air, water, and soil pollution harm living organisms and ecosystems.

• Ozone Depletion: CFCs thin the ozone layer, allowing harmful UV radiation to reach Earth.

• Biological Magnification: Harmful chemicals accumulate in food chains, affecting top consumers.

• Climate Change: Greenhouse gas emissions lead to global warming and climate change.

📝 How to Use These PYQs for CBSE Exam Preparation

At Dhingra Classes Nashik, we recommend the following strategies to maximize your score using these PYQs.

🎯 Study Tips

1. 📖 Read each question and try to answer before looking at the solution

2. ✏️ Practice writing answers within time limits (1 mark = 1 min, 3 marks = 5 min, 5 marks = 10 min)

3. 🗣️ Focus on repeated themes like food chains, ozone depletion, and biological magnification

4. 📝 Create flashcards for 1-mark questions

5. 🔬 Practice diagrams for food chains and food webs

6. 🔄 Revise weekly to ensure long-term retention

7. 📋 Practice Assertion-Reason questions as they are frequently asked

8. ✅ Take mock tests using these PYQs

🏫 How Dhingra Classes Nashik Helps Class 10 CBSE Students Master Science

At Dhingra Classes Nashik, we provide comprehensive coaching for Science and all other subjects for Class 10 CBSE students. Our approach includes:

• 📚 Structured Lessons: Teaching concepts with clear explanations

• 🔬 Diagram Practice: Regular diagram work for better understanding

• 📝 PYQ Analysis: Regular practice with previous year questions

• ✏️ Regular Tests: Weekly tests to ensure continuous revision

• 🎯 Doubt Clearing Sessions: Personalized attention to every student

• 📊 Progress Tracking: Regular updates to parents about student progress

• 🏆 Answer Writing Practice: Teaching how to structure answers for maximum marks

📞 Contact Dhingra Classes Nashik

• 📱 Phone: 98230 62106

• 📧 Email: dhingraclassesnsk@gmail.com

• 🌐 Website: www.dhingraclassesnashik.com

• 📍 Address: Plot No 3, XQ3G+H3M Deacon Homes, 301C, opp. Metro Zone, near Guru Govind Sing, Samarth Nagar, Dnyaneshwar Nagar, Pathardi Phata, Nashik, Maharashtra 422009

🏁 Conclusion

Mastering Our Environment PYQs is essential for Class 10 CBSE students to score high marks in Science board examinations. This comprehensive collection of 1-mark, 2-mark, 3-mark, and 5-mark questions covers all major themes including Ecosystem, Food Chain, Food Web, Trophic Levels, Energy Flow, Biodegradable Waste, Non-Biodegradable Waste, Ozone Depletion, and Waste Management.

By regularly practicing these Previous Year Questions and using them in your board exam preparation, you can improve your understanding and score better. At Dhingra Classes Nashik, we are committed to helping Class 10 CBSE students excel in Science and achieve academic success. Remember, Our Environment is not just about memorizing facts—it is about understanding how we can protect our planet for future generations.