Class 10th Science Chapter 15 – Our Environment and Sustainable Management | Biodegradable and Non-Biodegradable Waste

🌍 Our Environment and Sustainable Management

Biodegradable and Non-Biodegradable Waste

जैव निम्नीकरणीय एवं अजैव निम्नीकरणीय अपशिष्ट | CBSE Class 10 Science

♻️ Biodegradable and Non-Biodegradable Waste

1. Introduction | परिचय

Waste is any material or substance that is discarded because it is no longer required or useful for its original purpose.

अपशिष्ट (Waste) वह पदार्थ है जिसे उसके मूल उपयोग के बाद अनुपयोगी समझकर त्याग दिया जाता है।

Waste can be classified into biodegradable and non-biodegradable on the basis of whether microorganisms can naturally break it down.

सूक्ष्मजीवों द्वारा प्राकृतिक रूप से विघटित किए जाने की क्षमता के आधार पर अपशिष्ट को मुख्यतः जैव निम्नीकरणीय और अजैव निम्नीकरणीय में बाँटा जाता है।

2. Biodegradable Waste | जैव निम्नीकरणीय अपशिष्ट

Definition: Biodegradable waste is waste that can be broken down naturally by microorganisms such as bacteria and fungi into simpler substances.

परिभाषा: ऐसा अपशिष्ट जिसे बैक्टीरिया और कवक जैसे सूक्ष्मजीव प्राकृतिक रूप से सरल पदार्थों में विघटित कर सकते हैं, जैव निम्नीकरणीय अपशिष्ट कहलाता है।

🍎

🥬

🍂

🦠

🌱

Examples include:

• Fruit and vegetable peels
• Food waste
• Leaves and grass
• Paper in suitable conditions
• Cotton and many natural fibres
• Animal dung
• Garden waste

3. Non-Biodegradable Waste | अजैव निम्नीकरणीय अपशिष्ट

Definition: Non-biodegradable waste is waste that microorganisms cannot readily break down into simpler substances within a short natural period.

परिभाषा: ऐसा अपशिष्ट जिसे सामान्य प्राकृतिक परिस्थितियों में सूक्ष्मजीव आसानी से और कम समय में सरल पदार्थों में नहीं तोड़ पाते, अजैव निम्नीकरणीय अपशिष्ट कहलाता है।

🥤 Plastic
प्लास्टिक

🥫 Metal Can
धातु का डिब्बा

🧴 Synthetic Material
कृत्रिम पदार्थ

💻 E-waste
ई-कचरा

4. Main Difference | मुख्य अंतर

🌱 Biodegradable

• Microorganisms can break it down.
• Usually decomposes relatively faster.
• Can return nutrients to ecosystems.
• Can often be treated through composting.
• Examples: food waste, leaves, dung.

♻️ Non-Biodegradable

• Does not readily decompose by microorganisms.
• May persist for a very long time.
• Can accumulate in the environment.
• Requires segregation, reuse, recycling or safe disposal.
• Examples: plastics, many synthetic materials.

5. Comparison Table | तुलना तालिका

Basis	Biodegradable	Non-Biodegradable
Meaning	Can be broken down naturally by microorganisms.	Does not readily break down naturally in a short period.
Decomposition	Generally comparatively faster.	Generally very slow or difficult.
Accumulation	Usually less persistent.	Can accumulate for long periods.
Examples	Food, leaves, vegetable peels.	Plastic, many synthetic materials.
Management	Composting, biological treatment.	Reduce, reuse, recycle and safe disposal.

6. Role of Microorganisms | सूक्ष्मजीवों की भूमिका

Microorganisms such as bacteria and fungi act as decomposers. They break down dead organic matter into simpler substances and help return nutrients to the environment.

बैक्टीरिया और कवक जैसे सूक्ष्मजीव अपघटक के रूप में कार्य करते हैं। वे मृत कार्बनिक पदार्थों को सरल पदार्थों में बदलकर पोषक तत्वों को पर्यावरण में वापस पहुँचाने में सहायता करते हैं।

🍂 Organic Waste

→

🦠 Decomposers

→

🌱 Simpler Substances

→

♻️ Nutrient Recycling

7. Examples of Biodegradable Waste | उदाहरण

Waste Material	Biodegradable?	Reason / Management
Vegetable peels	Yes	Can decompose naturally; suitable for composting.
Fruit waste	Yes	Organic matter decomposes through microorganisms.
Leaves	Yes	Decompose naturally and contribute to soil organic matter.
Food leftovers	Yes	Can be composted under suitable conditions.
Animal dung	Yes	Can be biologically decomposed and used for manure/biogas.

8. Examples of Non-Biodegradable Waste | उदाहरण

Waste Material	Nature	Environmental Concern
Plastic bags	Non-biodegradable	Persistent pollution and wildlife risks.
Plastic bottles	Non-biodegradable	Long persistence; requires recovery/recycling.
Many synthetic fibres	Non-biodegradable/persistent	Can persist and generate microplastic pollution.
Electronic waste	Complex and persistent	May contain hazardous substances and valuable recoverable materials.
Some synthetic chemicals	Persistent	May remain in the environment and enter food chains.

9. Environmental Problems Caused by Non-Biodegradable Waste

Non-biodegradable waste can remain in the environment for long periods and may cause pollution when it is improperly discarded.

Major problems include:

• Accumulation of waste in land and water.
• Blockage of drains and waterways.
• Ingestion or entanglement risks for animals.
• Microplastic formation from degradation of some plastics.
• Visual pollution.
• Possible release of hazardous substances from poorly managed waste.
• Contribution to landfill burden.

10. Biodegradable Waste and Composting | जैविक कचरा एवं कम्पोस्टिंग

Composting is a controlled biological process in which suitable organic waste is decomposed by microorganisms to produce nutrient-rich compost.

कम्पोस्टिंग एक नियंत्रित जैविक प्रक्रिया है जिसमें उपयुक्त जैविक अपशिष्ट सूक्ष्मजीवों द्वारा विघटित होकर पोषक तत्वों से भरपूर कम्पोस्ट में बदलता है।

🍎 Food Waste

→

🦠 Decomposition

→

🌿 Compost

→

🌱 Soil Nutrients

11. Waste Segregation | अपशिष्ट पृथक्करण

Waste segregation means separating different categories of waste at the point of generation.

अपशिष्ट पृथक्करण का अर्थ है कचरे को उत्पन्न होने के स्थान पर ही अलग-अलग श्रेणियों में बाँटना।

Basic Principle:
Wet/organic waste → Composting or biological treatment
Dry recyclable waste → Collection and recycling
Hazardous/special waste → Appropriate safe handling and disposal

Local waste-bin colours and collection systems may vary by municipality. Always follow the applicable local waste-management instructions.

12. 3R Principle | 3R सिद्धांत

1. Reduce
कम उपयोग करें

→

2. Reuse
पुनः उपयोग करें

→

3. Recycle
पुनर्चक्रण करें

Reduce: Unnecessary consumption and waste generation को कम करना।
Reuse: वस्तु को बार-बार उपयोग करना।
Recycle: उपयुक्त अपशिष्ट को संसाधित करके उपयोगी नए पदार्थ बनाना।

13. Why Should Plastic Waste Be Reduced? | प्लास्टिक कचरा कम क्यों करें?

Many conventional plastics are persistent and do not readily decompose through ordinary biological processes. Improperly discarded plastic can accumulate on land and in water and may harm animals.

Better approach:

• Avoid unnecessary single-use items.
• Carry reusable alternatives.
• Segregate plastic for proper collection.
• Reuse where safe and appropriate.
• Send recyclable plastic to authorized recycling systems where available.

14. Waste Management Hierarchy | अपशिष्ट प्रबंधन क्रम

🚫 Prevent

→

⬇️ Reduce

→

🔄 Reuse

→

♻️ Recycle

→

🗑️ Safe Disposal

The best waste-management strategy is generally to prevent unnecessary waste generation first, followed by reduction, reuse and recycling where feasible.

15. Important Concept: Biodegradable Does Not Mean Completely Harmless

A biodegradable material can still cause environmental problems if generated in excessive quantities or disposed of improperly. Decomposition may also produce gases, odours or other environmental effects depending on conditions.

Therefore, the goal is not simply to choose biodegradable materials, but to follow responsible consumption, segregation, treatment and disposal.

16. 30 MCQs | बहुविकल्पीय प्रश्न

1. Which type of waste can generally be broken down by microorganisms?

A. Biodegradable waste

B. Non-biodegradable waste

C. Metallic waste only

D. Glass only

Answer: A — Biodegradable waste

2. Which is a biodegradable material?

A. Plastic bottle

B. Vegetable peel

C. Synthetic fibre

D. Plastic bag

Answer: B — Vegetable peel

3. Which organism group plays an important role in decomposition?

A. Only birds

B. Only mammals

C. Bacteria and fungi

D. Only reptiles

Answer: C — Bacteria and fungi

4. Which is generally non-biodegradable?

A. Fruit peel

B. Dry leaves

C. Food waste

D. Conventional plastic bag

Answer: D — Conventional plastic bag

5. Composting is mainly used for:

A. Suitable organic waste

B. Glass only

C. Metal only

D. Plastic bottles only

Answer: A — Suitable organic waste

6. Which principle means using an item again?

A. Reduce

B. Reuse

C. Recycle

D. Recover

Answer: B — Reuse

7. Which principle means processing waste to make useful new material?

A. Reduce

B. Reuse

C. Recycle

D. Refuse

Answer: C — Recycle

8. Which waste may persist for a very long time?

A. Food waste

B. Vegetable peel

C. Fresh leaves

D. Many plastics

Answer: D — Many plastics

9. Which is a biodegradable waste?

A. Animal dung

B. Plastic wrapper

C. Glass bottle

D. Aluminium can

Answer: A — Animal dung

10. Which is the most appropriate first step in waste management?

A. Generate more waste

B. Prevent unnecessary waste

C. Burn all waste

D. Throw waste into water

Answer: B — Prevent unnecessary waste

11. Biodegradation is carried out mainly by:

A. Microorganisms

B. Rocks

C. Sunlight only

D. Metals

Answer: A — Microorganisms

12. Which item is suitable for composting under appropriate conditions?

A. Food scraps

B. Plastic bottle

C. Glass

D. Metal can

Answer: A — Food scraps

13. Non-biodegradable waste can cause:

A. Only soil formation

B. Environmental accumulation

C. Immediate decomposition

D. Nutrient recycling only

Answer: B — Environmental accumulation

14. Which is a natural organic waste?

A. Plastic sheet

B. Glass

C. Fallen leaf

D. Aluminium foil

Answer: C — Fallen leaf

15. Which one belongs to the 3R principle?

A. Reduce

B. Reject all recycling

C. Release waste

D. Remove nutrients

Answer: A — Reduce

16. Which is an example of reuse?

A. Throwing away a bottle

B. Using a durable container repeatedly

C. Burning plastic

D. Dumping waste

Answer: B — Using a durable container repeatedly

17. Which material generally requires special management because it may contain hazardous substances?

A. E-waste

B. Vegetable peel

C. Leaves

D. Fruit waste

Answer: A — E-waste

18. Which waste is most suitable for biological decomposition?

A. Organic food waste

B. Glass

C. Metal

D. Plastic

Answer: A — Organic food waste

19. Waste segregation means:

A. Mixing all waste

B. Separating different waste categories

C. Burning all waste

D. Dumping waste in rivers

Answer: B — Separating different waste categories

20. Which waste may form microplastics as larger plastic items break down?

A. Plastic waste

B. Fruit waste

C. Leaf litter

D. Food waste

Answer: A — Plastic waste

21. Which of the following is biodegradable?

A. Cotton cloth

B. Plastic wrapper

C. Glass bottle

D. Aluminium can

Answer: A — Cotton cloth

22. Which is generally non-biodegradable?

A. Leaves

B. Vegetable waste

C. Many synthetic plastics

D. Food waste

Answer: C — Many synthetic plastics

23. Decomposers help in:

A. Nutrient recycling

B. Increasing plastic pollution

C. Producing all metals

D. Stopping all decomposition

Answer: A — Nutrient recycling

24. Which practice can reduce waste generation?

A. Unnecessary single-use consumption

B. Buying only what is needed

C. Throwing usable goods away

D. Mixing all waste

Answer: B — Buying only what is needed

25. Which is an example of recycling?

A. Sending suitable used paper for recycling

B. Throwing paper into a drain

C. Burning all paper outdoors

D. Mixing paper with wet waste

Answer: A

26. Which statement is correct?

A. Every biodegradable material is harmless in every quantity.

B. Biodegradable waste can still cause problems if improperly managed.

C. All waste is biodegradable.

D. Non-biodegradable waste always disappears quickly.

Answer: B

27. Which waste should generally be kept separate from ordinary household waste?

A. Hazardous/special waste

B. Vegetable peel

C. Fruit peel

D. Garden leaves

Answer: A

28. Which activity directly supports decomposition of organic waste?

A. Composting

B. Plastic production

C. Metal mining

D. Glass polishing

Answer: A — Composting

29. Which is the best description of biodegradable waste?

A. Waste that cannot ever change

B. Waste that microorganisms can break down naturally

C. Only metallic waste

D. Only electronic waste

Answer: B

30. The main objective of sustainable waste management is to:

A. Increase waste generation

B. Protect resources and reduce environmental impact

C. Mix all waste

D. Dump waste into water

Answer: B

17. 30 Important Subjective Questions | वर्णनात्मक प्रश्न

2 Marks
Q1. What is biodegradable waste?

Waste that can be broken down naturally by microorganisms into simpler substances is called biodegradable waste.

2 Marks
Q2. What is non-biodegradable waste?

Waste that does not readily decompose through ordinary biological processes within a short natural period is called non-biodegradable waste.

2 Marks
Q3. Give two examples of biodegradable waste.

Vegetable peels and fallen leaves.

2 Marks
Q4. Give two examples of non-biodegradable waste.

Plastic bags and many synthetic materials.

2 Marks
Q5. Name two groups of microorganisms involved in decomposition.

Bacteria and fungi.

2 Marks
Q6. What is waste segregation?

Waste segregation means separating waste into different categories at the place where it is generated.

3 Marks
Q7. Differentiate between biodegradable and non-biodegradable waste.

Biodegradable waste is naturally broken down by microorganisms, while non-biodegradable waste does not readily break down through ordinary biological processes. Biodegradable waste is generally less persistent; non-biodegradable waste may accumulate for long periods.

3 Marks
Q8. Why are microorganisms important in an ecosystem?

They decompose dead organic matter and help release and recycle nutrients into the environment.

3 Marks
Q9. What is composting?

Composting is a controlled biological decomposition process in which suitable organic waste is converted into nutrient-rich compost.

3 Marks
Q10. Explain the 3R principle.

Reduce unnecessary consumption, reuse products wherever practical, and recycle suitable materials.

3 Marks
Q11. Why can non-biodegradable waste be harmful?

It can persist and accumulate, pollute land and water, block drains, and cause risks to wildlife. Some types may also contain or release hazardous substances.

3 Marks
Q12. Why should waste be segregated?

Segregation allows organic waste to be biologically treated and recyclable or special wastes to be handled appropriately, improving recovery and reducing pollution.

4 Marks
Q13. Explain the role of decomposers in waste management.

Decomposers such as bacteria and fungi break down dead organic matter into simpler substances. Controlled biological decomposition can help manage organic waste and return nutrients to the environment.

4 Marks
Q14. Write four examples of biodegradable waste and four examples of non-biodegradable waste.

Biodegradable: food scraps, fruit peels, leaves, animal dung.
Non-biodegradable: plastic bags, plastic bottles, many synthetic materials, certain electronic components.

4 Marks
Q15. Explain why plastic waste is an environmental concern.

Many plastics persist for long periods, can accumulate on land and in water, may harm animals through ingestion or entanglement, and can contribute to microplastic pollution.

4 Marks
Q16. Explain how composting helps in waste management.

Composting biologically decomposes suitable organic waste and produces compost that can be used as a soil amendment. It reduces the amount of organic waste requiring disposal.

4 Marks
Q17. Explain the importance of Reduce, Reuse and Recycle.

Reduce lowers waste generation, reuse extends the useful life of products, and recycling recovers materials from suitable waste. Together they conserve resources and reduce disposal pressure.

5 Marks
Q18. Describe the harmful effects of improper disposal of non-biodegradable waste.

Improper disposal can cause land and water pollution, drain blockage, wildlife injury, visual pollution, persistent litter and, for certain materials, exposure to hazardous substances.

5 Marks
Q19. Explain how waste segregation supports sustainable waste management.

Segregation separates organic waste, recyclable materials and special/hazardous waste. This allows each stream to receive a suitable treatment, improves recycling and composting, and reduces contamination and disposal burden.

5 Marks
Q20. Explain the difference between decomposition and recycling.

Decomposition is the biological breakdown of organic matter by decomposers. Recycling is the processing and recovery of useful materials from waste so they can be used again in products or processes.

5 Marks
Q21. Why is it important to reduce waste generation at the source?

Preventing waste reduces the quantity that needs collection, treatment and disposal. It also conserves raw materials, energy and other resources and reduces pollution.

5 Marks
Q22. Explain the environmental importance of biodegradable waste decomposition.

Decomposition converts dead organic matter into simpler substances and helps return nutrients to the environment. Properly managed decomposition supports nutrient cycling and reduces uncontrolled accumulation of organic waste.

6 Marks
Q23. Explain biodegradable and non-biodegradable waste with examples, differences and management methods.

Biodegradable waste can be broken down by microorganisms and includes food waste, leaves and vegetable peels. It can often be treated through composting or other biological processes. Non-biodegradable waste does not readily decompose and includes many plastics and synthetic materials. It should be reduced, reused, recycled or safely disposed of according to its type.

6 Marks
Q24. Explain the role of microorganisms in maintaining environmental balance.

Microorganisms decompose dead organisms and organic waste, convert complex organic matter into simpler substances and help recycle nutrients. Without decomposition, organic matter would accumulate and nutrient cycling would be disrupted.

6 Marks
Q25. Describe a sustainable household waste-management system.

1. Prevent unnecessary purchases and waste.
2. Separate wet/organic and dry waste.
3. Compost suitable organic waste.
4. Reuse durable products.
5. Send recyclable materials to appropriate collection systems.
6. Handle hazardous and electronic waste through suitable authorized channels.

6 Marks
Q26. Compare biodegradable and non-biodegradable waste in tabular form.

Feature	Biodegradable	Non-Biodegradable
Microbial breakdown	Generally possible	Not readily possible
Persistence	Usually lower	Often high
Examples	Food waste, leaves	Plastic, many synthetic materials
Management	Composting/biological treatment	Reduce/reuse/recycle/safe disposal

6 Marks
Q27. Explain the importance of the 3R principle in environmental protection.

Reduce lowers the amount of resources consumed and waste generated. Reuse increases the useful life of products. Recycling recovers materials and reduces the demand for some virgin resources. Together, these practices reduce environmental pressure.

6 Marks
Q28. What problems may arise when waste is not properly segregated?

Organic and recyclable waste become mixed, reducing recycling and composting efficiency. Recyclables may become contaminated, hazardous materials may be handled unsafely, and the quantity sent to disposal facilities may increase.

6 Marks
Q29. Explain how non-biodegradable waste can affect food chains.

Persistent pollutants associated with some non-biodegradable waste can enter ecosystems. Certain substances may be taken up by organisms and can accumulate or biomagnify through food chains, potentially affecting organisms at higher trophic levels.

6 Marks
Q30. Explain why sustainable waste management is necessary for environmental protection.

Sustainable waste management reduces waste generation, promotes reuse and recycling, treats organic waste appropriately, prevents pollution and ensures special wastes are safely managed. It conserves resources and reduces pressure on ecosystems and disposal facilities.

18. Assertion–Reason Questions | अभिकथन–कारण

Q1. Assertion: Vegetable peels are generally biodegradable.
Reason: Microorganisms can decompose their organic matter.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

Q2. Assertion: Many plastics are persistent in the environment.
Reason: They do not readily undergo ordinary biological decomposition.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q3. Assertion: Composting is suitable for all types of waste.
Reason: Metals and plastics are converted into compost by microorganisms.

Answer: Both statements are false.

Q4. Assertion: Waste segregation improves waste management.
Reason: Different waste streams require different treatment and disposal methods.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q5. Assertion: Biodegradable waste is always harmless.
Reason: Microorganisms can decompose it.

Answer: Assertion is false, Reason is true.

19. HOTS / Competency-Based Questions | उच्च स्तरीय प्रश्न

HOTS 1: A school has food waste, plastic wrappers and paper. How should these be managed?

Food waste should be separated for composting/biological treatment, clean recyclable paper should be sent for recycling, and plastic wrappers should be segregated for appropriate collection/recycling or disposal according to the material and local system.

HOTS 2: Why is throwing plastic waste into a river harmful even though plastic may eventually break into smaller pieces?

Breaking into smaller pieces does not mean complete biodegradation. Plastic can persist as litter and microplastics, harm aquatic organisms and enter aquatic food webs.

HOTS 3: A household mixes kitchen waste with recyclable paper and plastic. What problems can arise?

Organic matter can contaminate recyclable materials, making recovery more difficult. Composting also becomes less efficient and the amount sent to disposal may increase.

HOTS 4: Why is “Reduce” placed before “Recycle” in the 3R principle?

Reducing consumption prevents waste from being generated in the first place, whereas recycling deals with waste after it has already been produced.

HOTS 5: Can biodegradable waste cause pollution? Explain.

Yes. Large quantities of improperly managed organic waste can produce odour, leachate and greenhouse gases under some decomposition conditions and can attract pests. Proper treatment such as composting helps manage these impacts.

20. Quick Revision Table | त्वरित पुनरावृत्ति

Concept	Key Point
Biodegradable	Can generally be broken down by microorganisms.
Non-Biodegradable	Does not readily decompose through ordinary biological processes.
Decomposers	Bacteria and fungi play major roles in decomposition.
Composting	Controlled biological treatment of suitable organic waste.
Segregation	Separating waste into appropriate categories.
Reduce	Prevent unnecessary waste generation.
Reuse	Use products again where practical.
Recycle	Recover/process suitable waste into useful materials.
Plastic Waste	Many plastics are persistent and require responsible management.
Sustainable Management	Reduce environmental impact while conserving resources.

21. Golden Points for Exam | परीक्षा के लिए महत्वपूर्ण बिंदु

• 🌱 Biodegradable waste can generally be decomposed by microorganisms.
• ♻️ Non-biodegradable waste does not readily decompose through ordinary biological processes.
• 🦠 Bacteria and fungi are important decomposers.
• 🍂 Food waste, leaves and vegetable peels are common biodegradable examples.
• 🛍️ Many plastics are common persistent non-biodegradable materials.
• 🌿 Composting is suitable for appropriate organic waste.
• 🗂️ Waste should be segregated at the source.
• 3️⃣ Remember the 3R principle: Reduce → Reuse → Recycle.
• 🌍 Biodegradable does not automatically mean harmless under every condition.
• 🚯 Improper disposal of persistent waste can cause long-term environmental problems.
• 💻 E-waste requires appropriate collection and treatment because it can contain hazardous and valuable materials.
• 🌎 Sustainable waste management helps conserve resources and reduce pollution.

CBSE Class 10 Science | Our Environment and Sustainable Management
Biodegradable and Non-Biodegradable Waste | जैव निम्नीकरणीय एवं अजैव निम्नीकरणीय अपशिष्ट

Class 10th Science Chapter 15 – Our Environment and Sustainable Management | Energy Flow and 10% Law

🌍 Our Environment and Sustainable Management

Energy Flow and 10% Law

ऊर्जा प्रवाह एवं 10% नियम | CBSE Class 10 Science

⚡ Energy Flow and 10% Law | ऊर्जा प्रवाह एवं 10% नियम

1. Introduction | परिचय

Energy Flow: Energy flow in an ecosystem refers to the transfer of energy from one organism to another through different trophic levels.

ऊर्जा प्रवाह: पारितंत्र में ऊर्जा का एक जीव से दूसरे जीव तक विभिन्न पोषण स्तरों के माध्यम से स्थानांतरण ऊर्जा प्रवाह कहलाता है।

Key Point | मुख्य बिंदु:
Energy flow in an ecosystem is unidirectional, meaning that energy moves in one direction and does not return to the previous trophic level.

पारितंत्र में ऊर्जा प्रवाह एकदिशीय (Unidirectional) होता है।

2. Main Source of Energy | ऊर्जा का मुख्य स्रोत

For most ecosystems, the Sun is the primary source of energy. अधिकांश पारितंत्रों के लिए सूर्य ऊर्जा का प्राथमिक स्रोत है।

☀️ Sun
सूर्य

→

🌱 Producers
उत्पादक

→

🐇 Primary Consumers
प्राथमिक उपभोक्ता

→

🦊 Secondary Consumers
द्वितीयक उपभोक्ता

→

🦅 Tertiary Consumers
तृतीयक उपभोक्ता

3. Energy Entry into Ecosystem | पारितंत्र में ऊर्जा का प्रवेश

Green plants and other photosynthetic organisms capture solar energy during photosynthesis and convert it into chemical energy stored in food. हरे पौधे एवं अन्य प्रकाश-संश्लेषी जीव प्रकाश-संश्लेषण के दौरान सौर ऊर्जा को ग्रहण करके उसे भोजन में संग्रहित रासायनिक ऊर्जा में बदलते हैं।

Solar Energy → Photosynthesis → Chemical Energy in Food
सौर ऊर्जा → प्रकाश-संश्लेषण → भोजन में रासायनिक ऊर्जा

Remember: Producers are the first trophic level because they introduce energy into the food chain in the form of organic food.
याद रखें: उत्पादक प्रथम पोषण स्तर होते हैं।

4. Energy Transfer Through Trophic Levels | पोषण स्तरों में ऊर्जा स्थानांतरण

Trophic Level	Organism	Example	Energy Role
1st	Producer	Grass, plants	Captures solar energy
2nd	Primary Consumer	Deer, rabbit	Gets energy by eating producers
3rd	Secondary Consumer	Frog, small fish	Gets energy by eating primary consumers
4th	Tertiary Consumer	Snake, eagle	Gets energy by eating secondary consumers

5. 10% Law of Energy Transfer | ऊर्जा स्थानांतरण का 10% नियम

The 10% law states that approximately only 10% of the energy available at one trophic level is transferred to the next trophic level.

10% नियम: किसी एक पोषण स्तर पर उपलब्ध ऊर्जा का लगभग केवल 10% ही अगले पोषण स्तर तक पहुँचता है।

Energy transferred to next trophic level = 10% × Energy available at previous trophic level

Important: About 90% of the energy does not become available to the next trophic level. A large part is used in life processes and much energy is dissipated as heat.

महत्वपूर्ण: लगभग 90% ऊर्जा अगले पोषण स्तर को उपलब्ध नहीं होती। ऊर्जा का बड़ा भाग जीवन-क्रियाओं में उपयोग होता है तथा बहुत-सी ऊर्जा ऊष्मा के रूप में नष्ट/विक्षेपित होती है।

6. Numerical Example of 10% Law | 10% नियम का संख्यात्मक उदाहरण

Suppose producers contain 10,000 J of available energy.

Producers10,000 J

Primary Consumers1,000 J

Secondary Consumers100 J

Tertiary Consumers10 J

10,000 J → 1,000 J → 100 J → 10 J

Calculation:
10% of 10,000 J = 1,000 J
10% of 1,000 J = 100 J
10% of 100 J = 10 J

7. Why Does Energy Decrease at Higher Trophic Levels? | ऊर्जा क्यों घटती है?

Energy decreases at successive trophic levels because organisms use energy for:

• Respiration
• Movement
• Growth
• Reproduction
• Body maintenance
• Other metabolic activities

A significant amount of energy is ultimately released as heat.

हिंदी: प्रत्येक पोषण स्तर पर जीव ऊर्जा का उपयोग श्वसन, गति, वृद्धि, प्रजनन, शरीर के रख-रखाव तथा अन्य उपापचयी क्रियाओं में करते हैं। इसलिए अगले स्तर के लिए कम ऊर्जा उपलब्ध रहती है।

8. Unidirectional Flow of Energy | एकदिशीय ऊर्जा प्रवाह

☀️ Sun

→

🌱 Producers

→

🐇 Herbivores

→

🦊 Carnivores

→

🔥 Heat

Important Difference:
Nutrients can be recycled in an ecosystem, but energy is not recycled in the same way. Energy ultimately dissipates as heat.

महत्वपूर्ण: पोषक तत्वों का पुनर्चक्रण हो सकता है, लेकिन ऊर्जा उसी प्रकार पुनर्चक्रित नहीं होती; अंततः यह ऊष्मा के रूप में विक्षेपित होती है।

9. Energy Flow Through a Food Chain | खाद्य श्रृंखला में ऊर्जा प्रवाह

🌿 Grass
घास

→

🐗 Grasshopper
टिड्डा

→

🐸 Frog
मेंढक

→

🐍 Snake
साँप

→

🦅 Eagle
गरुड़

At every step, only a small fraction of the available energy is passed to the next organism.

प्रत्येक चरण में उपलब्ध ऊर्जा का केवल एक छोटा भाग अगले जीव तक पहुँचता है।

10. Energy Pyramid | ऊर्जा पिरामिड

An energy pyramid represents the amount of energy available at different trophic levels.

🌱 Producers – 10,000 J

🐇 Primary Consumers – 1,000 J

🐸 Secondary Consumers – 100 J

🦅 Tertiary Consumers – 10 J

Key Point: The pyramid of energy is always upright because energy decreases at successive trophic levels.

मुख्य बिंदु: ऊर्जा का पिरामिड हमेशा सीधा होता है क्योंकि प्रत्येक पोषण स्तर पर ऊर्जा कम होती जाती है।

11. Applications of 10% Law | 10% नियम के उपयोग

The 10% law helps us understand:

• Why food chains usually have limited trophic levels.
• Why top carnivores receive much less energy.
• Why energy pyramids are always upright.
• Why large populations of top predators cannot usually be supported by a small producer base.
• Why energy decreases rapidly along a food chain.

12. Important Numerical Examples | महत्वपूर्ण संख्यात्मक उदाहरण

Example 1: Producers contain 20,000 J energy. How much energy reaches the primary consumers?

10% of 20,000 = 2,000 J

Example 2: If primary consumers receive 800 J, how much reaches secondary consumers?

10% of 800 = 80 J

Example 3: If producers have 50,000 J, calculate energy available to tertiary consumers after three transfers.

50,000 → 5,000 → 500 → 50 J

Example 4: If 40 J reaches tertiary consumers, estimate the energy at producers under the simple 10% model.

40 J ÷ 10% = 400 J at secondary
400 ÷ 10% = 4,000 J at primary
4,000 ÷ 10% = 40,000 J at producers

13. 30 MCQs | बहुविकल्पीय प्रश्न

1. The primary source of energy for most ecosystems is:

A. Sun

B. Soil

C. Water

D. Oxygen

Answer: A — Sun

2. Energy flow in an ecosystem is:

A. Circular

B. Unidirectional

C. Random

D. Bidirectional

Answer: B — Unidirectional

3. Producers generally occupy which trophic level?

A. Second

B. Third

C. First

D. Fourth

Answer: C — First

4. According to the 10% law, approximately how much energy passes to the next trophic level?

A. 50%

B. 25%

C. 90%

D. 10%

Answer: D — 10%

5. If producers have 10,000 J, primary consumers receive approximately:

A. 1,000 J

B. 100 J

C. 10 J

D. 9,000 J

Answer: A — 1,000 J

6. If primary consumers receive 1,000 J, secondary consumers receive approximately:

A. 1,000 J

B. 100 J

C. 10 J

D. 900 J

Answer: B — 100 J

7. Which pyramid is always upright?

A. Pyramid of numbers

B. Pyramid of biomass

C. Pyramid of energy

D. None

Answer: C — Pyramid of energy

8. Most energy lost from an organism is ultimately dissipated as:

A. Water

B. Oxygen

C. Minerals

D. Heat

Answer: D — Heat

9. The first trophic level contains:

A. Producers

B. Herbivores

C. Carnivores

D. Decomposers only

Answer: A — Producers

10. The 10% law is related to:

A. Water cycling

B. Energy transfer

C. Nitrogen fixation

D. Population growth

Answer: B — Energy transfer

11. If producers have 5,000 J, primary consumers receive:

A. 5 J

B. 50 J

C. 500 J

D. 4,500 J

Answer: C — 500 J

12. Which process captures solar energy in an ecosystem?

A. Respiration

B. Excretion

C. Digestion

D. Photosynthesis

Answer: D — Photosynthesis

13. Energy at higher trophic levels is generally:

A. Greater

B. Equal

C. Lower

D. Unlimited

Answer: C — Lower

14. Which organism generally represents a primary consumer?

A. Grass

B. Deer

C. Tiger

D. Eagle

Answer: B — Deer

15. A food chain begins with:

A. Producer

B. Secondary consumer

C. Tertiary consumer

D. Decomposer

Answer: A — Producer

16. If 2,000 J is available at one trophic level, the next receives approximately:

A. 2 J

B. 20 J

C. 200 J

D. 1,800 J

Answer: C — 200 J

17. Energy transfer is inefficient mainly because organisms:

A. Do not respire

B. Use energy in life processes

C. Produce sunlight

D. Stop growing

Answer: B — Use energy in life processes

18. The energy pyramid represents:

A. Number of species only

B. Soil minerals

C. Rainfall

D. Energy available at trophic levels

Answer: D — Energy available at trophic levels

19. Energy stored by plants is mainly present as:

A. Chemical energy in organic matter

B. Sound energy

C. Magnetic energy

D. Nuclear energy

Answer: A — Chemical energy in organic matter

20. The approximate energy available at tertiary consumers if producers have 10,000 J is:

A. 1,000 J

B. 100 J

C. 10 J

D. 9,000 J

Answer: C — 10 J

21. Which statement is correct?

A. Energy increases at every trophic level

B. Energy remains constant

C. Energy is completely recycled

D. Energy decreases at successive trophic levels

Answer: D

22. In a food chain, arrows generally show:

A. Direction of energy/food transfer

B. Direction of rainfall

C. Direction of wind

D. Direction of population growth

Answer: A

23. If producers contain 30,000 J, energy at primary consumers is approximately:

A. 3 J

B. 300 J

C. 3,000 J

D. 27,000 J

Answer: C — 3,000 J

24. Which level generally receives the least energy?

A. Producers

B. Primary consumers

C. Secondary consumers

D. Highest trophic level

Answer: D — Highest trophic level

25. The energy flow in an ecosystem starts mainly from:

A. Sun

B. Decomposers

C. Soil

D. Carnivores

Answer: A — Sun

26. A food chain with more trophic levels generally has:

A. More energy at the top

B. Less energy at the top

C. Equal energy at all levels

D. No energy loss

Answer: B — Less energy at the top

27. If 100 J reaches a secondary consumer, approximately how much can reach the tertiary consumer?

A. 1 J

B. 10 J

C. 50 J

D. 90 J

Answer: B — 10 J

28. Which statement about energy and nutrients is correct?

A. Both are recycled identically

B. Neither changes

C. Energy is not recycled in the same way as nutrients

D. Nutrients are never recycled

Answer: C

29. A major reason for fewer top predators is:

A. Low energy availability at higher trophic levels

B. No sunlight

C. No oxygen

D. No water

Answer: A

30. The 10% law gives an approximate value for:

A. Water transfer

B. Energy transfer

C. Oxygen production

D. Soil formation

Answer: B — Energy transfer

14. 30 Important Subjective Questions | वर्णनात्मक प्रश्न

2 Marks
Q1. What is energy flow in an ecosystem?

Energy flow is the transfer of energy from the Sun to producers and then through successive trophic levels.
ऊर्जा प्रवाह सूर्य से उत्पादकों तथा फिर विभिन्न पोषण स्तरों तक ऊर्जा के स्थानांतरण को कहते हैं।

2 Marks
Q2. Why is the Sun called the primary source of energy?

Because most ecosystems ultimately obtain their energy from solar radiation captured by producers.

2 Marks
Q3. What is meant by the 10% law?

Only about 10% of energy available at one trophic level is transferred to the next trophic level.

2 Marks
Q4. What happens to the remaining energy?

Much is used in life processes and much is ultimately dissipated as heat.

2 Marks
Q5. Why is energy flow unidirectional?

Energy enters mainly as sunlight, passes through trophic levels and ultimately dissipates as heat; it is not returned to the Sun or previous trophic level.

2 Marks
Q6. Calculate 10% of 5,000 J.

10% × 5,000 = 500 J

3 Marks
Q7. Explain energy transfer from producers to secondary consumers.

Producers capture solar energy and store it as chemical energy. Primary consumers obtain a fraction of this energy by feeding on producers. Secondary consumers obtain about 10% of the energy available at the primary consumer level.

3 Marks
Q8. Explain the 10% law with an example.

If producers have 10,000 J, primary consumers receive 1,000 J, secondary consumers 100 J and tertiary consumers 10 J under the simple 10% model.

3 Marks
Q9. Why does energy decrease at each trophic level?

Organisms use energy for respiration, movement, growth, reproduction and maintenance. Much of the energy is eventually released as heat, leaving less energy for the next level.

3 Marks
Q10. Why is the energy pyramid always upright?

Because only a fraction of energy is transferred to each successive trophic level. Therefore energy available decreases upward.

3 Marks
Q11. Differentiate between energy flow and nutrient cycling.

Energy flows through the ecosystem in one direction and is eventually dissipated as heat, whereas nutrients can circulate between living organisms and the physical environment.

4 Marks
Q12. Describe the pathway of energy in a simple ecosystem.

Sun → producers → primary consumers → secondary consumers → tertiary consumers. At every transfer, most available energy is used or dissipated as heat, while only a fraction becomes available to the next trophic level.

4 Marks
Q13. Explain the significance of the 10% law.

It explains the rapid decrease of energy at higher trophic levels, the upright nature of the energy pyramid, the limited length of food chains and the comparatively small energy supply available to top consumers.

4 Marks
Q14. Explain energy flow using a food chain.

Grass → Grasshopper → Frog → Snake → Eagle. Energy captured by grass is transferred through consumers, but only a small fraction reaches each next level.

4 Marks
Q15. What is the role of producers in energy flow?

Producers capture solar energy through photosynthesis and convert it into chemical energy in organic matter. This stored energy becomes available to consumers when they feed on producers.

5 Marks
Q16. Explain the 10% law with a suitable energy pyramid.

For example:
Producers = 10,000 J
Primary consumers = 1,000 J
Secondary consumers = 100 J
Tertiary consumers = 10 J

The energy decreases by approximately a factor of 10 at every transfer.

5 Marks
Q17. Why cannot an ecosystem support unlimited trophic levels?

Only a small fraction of energy is transferred to the next level. After several transfers, very little energy remains available to support another trophic level. Therefore food chains generally remain limited in length.

5 Marks
Q18. Explain why top carnivores are fewer in number in many ecosystems.

Higher trophic levels receive much less usable energy. Since energy decreases strongly upward, the ecosystem can support fewer organisms at the highest trophic levels.

5 Marks
Q19. Explain the relationship between food chain and energy flow.

A food chain describes feeding relationships, while energy flow describes the transfer of energy through those feeding relationships. When one organism eats another, some stored energy is transferred to the consumer.

5 Marks
Q20. Describe why energy is not recycled in an ecosystem like nutrients.

Energy enters mainly from sunlight, passes through organisms and is eventually dissipated as heat. Nutrients, in contrast, can be released and reused through biogeochemical cycles.

6 Marks
Q21. Describe energy flow in an ecosystem with a labelled sequence.

Sun → Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers → Heat loss.

Producers capture solar energy. Consumers obtain energy by feeding on other organisms. Only a small fraction is transferred at each level, while much is used in metabolism and dissipated as heat. Thus energy flow is unidirectional.

6 Marks
Q22. Explain the 10% law using a numerical example of 20,000 J.

Producers = 20,000 J
Primary consumers = 2,000 J
Secondary consumers = 200 J
Tertiary consumers = 20 J

Each next trophic level receives approximately 10% of the energy available at the previous level.

6 Marks
Q23. Explain why energy pyramids are always upright.

Energy is lost at every trophic transfer. Only about 10% is transferred under the 10% law, while the rest is used in life processes or dissipated as heat. Therefore energy is highest at the producer level and progressively lower at higher levels.

6 Marks
Q24. Explain the importance of energy flow for ecosystem stability.

Energy flow determines how much energy is available to organisms at each trophic level. Adequate energy supports growth, reproduction and survival. Since energy decreases at higher levels, the number and biomass of organisms that can be supported also become limited.

6 Marks
Q25. Compare energy flow and nutrient cycling.

Energy Flow	Nutrient Cycling
Unidirectional	Cyclic
Enters mainly as solar energy	Moves between biotic and abiotic components
Eventually dissipated as heat	Can be reused

6 Marks
Q26. A food chain contains four trophic levels. Explain the expected trend in energy at these levels.

The first level has the greatest available energy. Approximately 10% reaches the second level, 10% of that reaches the third, and 10% of that reaches the fourth. Therefore the fourth trophic level has much less energy than the first.

6 Marks
Q27. Explain the importance of producers in maintaining energy flow.

Producers convert solar radiation into chemical energy through photosynthesis. This stored energy enters food chains and supports herbivores and higher consumers. Without primary producers, most ecosystems would not have a continuing external energy input.

6 Marks
Q28. Explain the statement: “Energy flow is unidirectional but nutrients are recycled.”

Energy moves from the Sun to producers and then through consumers, finally dissipating as heat. Nutrients such as carbon, nitrogen and minerals can move between organisms and the environment and be reused. Hence energy flow is directional while nutrient movement is cyclic.

6 Marks
Q29. Calculate energy available at each trophic level if producers contain 80,000 J.

Producers = 80,000 J
Primary consumers = 8,000 J
Secondary consumers = 800 J
Tertiary consumers = 80 J

6 Marks
Q30. Explain the importance of the 10% law in understanding food chains.

The 10% law explains why energy declines rapidly along a food chain. It helps explain the upright energy pyramid, limited food-chain length and the relatively small amount of energy available to top consumers. It also shows why a large producer base is required to support higher trophic levels.

15. Assertion–Reason Questions | अभिकथन–कारण

Q1. Assertion: Energy flow in an ecosystem is unidirectional.
Reason: Energy ultimately dissipates as heat and is not returned to the previous trophic level.

Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.

Q2. Assertion: The energy pyramid is always upright.
Reason: Energy available decreases at successive trophic levels.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q3. Assertion: Primary consumers generally receive less energy than producers.
Reason: Only a fraction of producer energy is transferred to consumers.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q4. Assertion: Energy is recycled in an ecosystem exactly like nutrients.
Reason: Energy can be reused indefinitely after being released as heat.

Answer: Both statements are false.

Q5. Assertion: Top trophic levels usually have less available energy.
Reason: Energy is lost at every trophic transfer.

Answer: Both are true, and the Reason correctly explains the Assertion.

16. HOTS / Competency-Based Questions | उच्च स्तरीय प्रश्न

HOTS 1: A farmer has 100,000 J stored in plants. Estimate the energy available to the secondary consumers under the 10% model.

100,000 → 10,000 → 1,000 J

HOTS 2: Why is eating lower on a food chain sometimes associated with greater energy availability?

Because fewer trophic transfers occur, so less energy has been lost through metabolic processes and heat dissipation.

HOTS 3: If producers are reduced drastically, what will happen to higher trophic levels?

Less energy will enter the food chain, so consumers at higher trophic levels will eventually face reduced food and energy availability.

HOTS 4: A food chain has producers with 60,000 J. How much energy reaches the third trophic level?

60,000 → 6,000 → 600 J

HOTS 5: Why does a long food chain generally contain less energy at its final level?

Because energy is lost at each transfer and only about 10% is passed to the next trophic level under the simple 10% model.

17. Quick Revision Table | त्वरित पुनरावृत्ति

Concept	Key Point
Energy Source	Sun is the primary source for most ecosystems.
Energy Entry	Producers capture solar energy through photosynthesis.
Energy Flow	Unidirectional.
10% Law	Approximately 10% passes to the next trophic level.
Energy Loss	Much energy is used in life processes and dissipated as heat.
Energy Pyramid	Always upright.
Highest Energy	Generally at producer level.
Lowest Energy	Generally at the highest trophic level.

18. Golden Points for Exam | परीक्षा के लिए महत्वपूर्ण बिंदु

• ☀️ Sun is the primary source of energy for most ecosystems.
• 🌱 Producers form the first trophic level.
• ➡️ Energy flow is unidirectional.
• 🔟 Approximately 10% energy is transferred to the next trophic level.
• 🔥 Much of the remaining energy is used in life processes and dissipated as heat.
• 📉 Energy decreases at successive trophic levels.
• 🔺 Pyramid of energy is always upright.
• ♻️ Nutrients can be recycled, but energy is not recycled in the same way.
• 🐅 Higher trophic levels generally receive less available energy.
• 📚 The 10% law is an approximate ecological principle used to explain energy transfer between trophic levels.

CBSE Class 10 Science | Our Environment and Sustainable Management
Energy Flow and 10% Law | ऊर्जा प्रवाह एवं 10% नियम

Class 10th Science Chapter 15 – Our Environment and Sustainable Management | Food Chain, Food Web and Trophic Levels

Our Environment and Sustainable Management

Food Chain, Food Web and Trophic Levels

खाद्य श्रृंखला, खाद्य जाल एवं पोषी स्तर

Class 10 CBSE Science | Foundation | Competitive Preparation

🌱 Food Chain, Food Web and Trophic Levels

1. Introduction | परिचय

A food chain describes a sequence in which food and energy pass from one organism to another. A food web consists of interconnected food chains, while a trophic level represents the position occupied by an organism in a food chain.

हिंदी: खाद्य श्रृंखला वह क्रम है जिसमें भोजन और ऊर्जा एक जीव से दूसरे जीव तक स्थानांतरित होती है। कई खाद्य श्रृंखलाओं के आपस में जुड़ने से खाद्य जाल बनता है। खाद्य श्रृंखला में किसी जीव की स्थिति को उसका पोषी स्तर (Trophic Level) कहते हैं।

Sun → Producers → Primary Consumers → Secondary Consumers → Higher Consumers

Core Idea: Food chain = linear pathway; Food web = interconnected pathways; Trophic level = feeding position.

2. Food Chain | खाद्य श्रृंखला

A food chain is a linear sequence of organisms through which food and energy are transferred as one organism eats another.

हिंदी: खाद्य श्रृंखला जीवों का एक क्रम है जिसमें एक जीव दूसरे जीव को खाता है और भोजन तथा ऊर्जा का स्थानांतरण होता है।

🌱
Grass
Producer

→

🦗
Grasshopper
Primary Consumer

→

🐸
Frog
Secondary Consumer

→

🐍
Snake
Higher Consumer

→

🦅
Eagle
Top Consumer

Grass → Grasshopper → Frog → Snake → Eagle

3. Meaning of the Arrow in a Food Chain

The arrow in a food chain generally represents the direction of food and energy transfer. It is read as “is eaten by” or “energy passes to”.

Grass → Deer

This means: Deer eats grass and energy stored in grass becomes available to the deer.

Exam Trap: The arrow does not mean that the organism at the tail of the arrow eats the organism at the head. It indicates the direction of transfer: food/energy → eater.

4. Grazing Food Chain

A grazing food chain begins with living green plants or other photosynthetic producers.

🌿
Grass

→

🐇
Rabbit

→

🦊
Fox

Grass → Rabbit → Fox

Most familiar terrestrial food chains are examples of grazing food chains.

5. Aquatic Food Chain

Aquatic food chains commonly begin with microscopic producers such as phytoplankton, followed by zooplankton and larger aquatic animals.

🟢
Phytoplankton

→

🔬
Zooplankton

→

🐟
Small Fish

→

🐟
Large Fish

6. Examples of Food Chains

Environment	Food Chain
Grassland	Grass → Grasshopper → Frog → Snake → Eagle
Forest	Grass → Deer → Tiger
Pond	Phytoplankton → Zooplankton → Small Fish → Large Fish
Crop field	Wheat → Rat → Snake → Eagle
Garden	Leaves → Caterpillar → Bird → Hawk

7. Trophic Level | पोषी स्तर

A trophic level is the position occupied by an organism in a food chain according to its feeding relationship.

हिंदी: खाद्य श्रृंखला में भोजन प्राप्त करने के आधार पर किसी जीव की स्थिति को उसका पोषी स्तर कहते हैं।

🦅 Fourth Trophic Level
Tertiary / Higher Consumer

⬇️

🐸 Third Trophic Level
Secondary Consumer

⬇️

🐇 Second Trophic Level
Primary Consumer

⬇️

🌱 First Trophic Level
Producer

8. First Trophic Level – Producers

The first trophic level is occupied by producers. They manufacture organic food and introduce energy into the food chain.

TL 1 = Producers

Plants

Algae

Phytoplankton

9. Second Trophic Level – Primary Consumers

The second trophic level is occupied by primary consumers, which generally feed directly on producers.

TL 2 = Primary Consumers

Herbivores

Deer

Rabbit

10. Third Trophic Level – Secondary Consumers

The third trophic level is generally occupied by secondary consumers, which feed on primary consumers.

TL 3 = Secondary Consumers

Frog

Lizard

11. Fourth Trophic Level – Tertiary Consumers

The fourth trophic level may be occupied by tertiary consumers that feed on secondary consumers.

TL 4 = Tertiary Consumers

Snake

Large Predators

12. Important Trophic-Level Table

Trophic Level	Organism Type	Example
1st	Producer	Grass
2nd	Primary Consumer	Grasshopper
3rd	Secondary Consumer	Frog
4th	Tertiary Consumer	Snake
Higher level	Top Consumer	Eagle

13. Food Chain and Energy Flow

Energy enters most ecosystems through sunlight and is captured by producers. It then passes from producers to consumers through feeding relationships.

Sun → Producer → Primary Consumer → Secondary Consumer → Higher Consumer

Energy flow through an ecosystem is unidirectional. It is not recycled in the same way as nutrients.

14. 10% Law of Energy Transfer

According to the commonly taught 10% law, approximately 10% of the energy available at one trophic level is transferred to the next trophic level.

🌱 Producers
10,000 J

→

🐇 Primary
1,000 J

→

🐸 Secondary
100 J

→

🐍 Tertiary
10 J

Energy at next trophic level ≈ 10% of energy at previous trophic level

The remaining energy is not simply “destroyed”; much is used in life processes and ultimately dissipated as heat.

15. Why are Food Chains Usually Short?

Only a small fraction of energy is transferred to the next trophic level. Therefore, progressively less energy becomes available at higher trophic levels.

This is one important reason why ecosystems generally have only a limited number of trophic levels in a food chain.

16. Food Web | खाद्य जाल

A food web is a network of interconnected food chains in an ecosystem. It represents multiple feeding relationships.

हिंदी: किसी परितंत्र में कई खाद्य श्रृंखलाएँ जब आपस में जुड़ जाती हैं, तो खाद्य जाल बनता है।

🌱 Grass

🌾 Plants

🌿 Shrubs

🐇 Rabbit

🦗 Grasshopper

🐭 Rat

🐸 Frog

🐍 Snake

🦊 Fox

🦅 Eagle

🐯 Tiger

Multiple arrows between organisms represent interconnected feeding relationships.

17. Example of a Food Web

Consider an ecosystem containing grass, grasshoppers, rabbits, frogs, snakes and eagles. Grass may be eaten by both grasshoppers and rabbits. Grasshoppers may be eaten by frogs and birds. Snakes may eat frogs and rats, while eagles may eat snakes and other animals.

Grass → Grasshopper → Frog → Snake → Eagle

Grass → Rabbit → Snake → Eagle

Grass → Rabbit → Eagle

Grass → Rat → Snake → Eagle

These interconnected chains together form a food web.

18. Food Chain vs Food Web

Food Chain	Food Web
Usually a single linear feeding pathway.	Contains several interconnected feeding pathways.
Shows one main route of energy transfer.	Shows multiple routes of energy transfer.
Simple representation.	More complex representation.
Less representative of the complete feeding relationships of many ecosystems.	Represents greater complexity of actual ecosystems.

19. Why is a Food Web More Stable?

A food web can provide alternative food pathways. If one food source becomes scarce, a consumer may sometimes use another available food source.

Therefore, interconnected feeding relationships can contribute to ecosystem stability.

However, a food web is not completely immune to disturbance. Major environmental changes can affect many connected populations simultaneously.

20. Difference Between Food Chain and Trophic Level

Food Chain	Trophic Level
A sequence showing feeding relationships.	The position of an organism in that sequence.
Example: Grass → Deer → Tiger.	Grass = TL1, Deer = TL2, Tiger = TL3.

21. Difference Between Food Web and Trophic Level

A food web describes the network of feeding relationships, whereas trophic level identifies the feeding position of an organism within a particular food pathway.

22. Organism Can Have Different Trophic Positions

An organism can occupy different trophic positions in different food chains because its position depends on what it eats.

Plants → Human

Human acts as a primary consumer in this pathway.

Plants → Goat → Human

Human occupies a higher trophic position in this pathway.

This is particularly important for omnivores, which may eat both plants and animals.

23. Food Chain and Decomposers

Decomposers do not normally appear as a simple successive trophic level in the same way as producers and consumers. They act on dead organisms and wastes from different trophic levels.

Dead Producers + Dead Consumers + Organic Waste → Decomposers → Simpler Substances + Nutrients

24. Food Chain, Food Web and Nutrient Cycling

🌱
Producers

→

🐇
Consumers

→

🦅
Higher Consumers

↓

🍄 🦠
Decomposers

↓

♻️
Nutrients

↓

🌱
Producers

25. Important Examples for CBSE

Food Chain	Producer	Primary Consumer	Secondary Consumer
Grass → Grasshopper → Frog → Snake	Grass	Grasshopper	Frog
Grass → Rabbit → Fox	Grass	Rabbit	Fox
Phytoplankton → Zooplankton → Fish	Phytoplankton	Zooplankton	Fish
Wheat → Rat → Snake → Eagle	Wheat	Rat	Snake

26. Important Exam Concepts

✔ Producer: First trophic level.

✔ Primary consumer: Usually herbivore; second trophic level.

✔ Secondary consumer: Usually feeds on primary consumers; third trophic level.

✔ Tertiary consumer: Feeds on secondary consumers in a given chain.

✔ Food chain: Linear feeding pathway.

✔ Food web: Interconnected food chains.

✔ Arrow: Direction of food/energy transfer.

✔ Energy: Flows in one direction and decreases at successive trophic levels.

✔ Nutrients: Can be recycled through ecosystem processes.

27. 30 MCQs with Answers

1. What is a food chain?

A. A linear sequence of feeding relationships

B. A list of abiotic factors

C. A group of decomposers only

D. A chemical cycle

Answer: A

2. Which organism occupies the first trophic level?

A. Frog

B. Producer

C. Snake

D. Eagle

Answer: B

3. In Grass → Deer → Tiger, deer is a:

A. Producer

B. Secondary consumer

C. Primary consumer

D. Decomposer

Answer: C

4. In Grass → Grasshopper → Frog, frog is a:

A. Producer

B. Primary consumer

C. Decomposer

D. Secondary consumer

Answer: D

5. The arrow in a food chain generally shows:

A. Direction of food and energy transfer

B. Direction of animal movement

C. Direction of reproduction

D. Direction of rainfall

Answer: A

6. Which is the correct food chain?

A. Eagle → Snake → Grass → Frog

B. Grass → Grasshopper → Frog → Snake

C. Frog → Grass → Snake → Grasshopper

D. Snake → Grass → Frog → Eagle

Answer: B

7. A food web consists of:

A. Only producers

B. Only one food chain

C. Interconnected food chains

D. Only decomposers

Answer: C

8. Which is generally an aquatic producer?

A. Eagle

B. Snake

C. Large fish

D. Phytoplankton

Answer: D

9. In a grazing food chain, the first organism is generally:

A. A living producer

B. A carnivore

C. A decomposer

D. A top predator

Answer: A

10. The second trophic level is generally occupied by:

A. Producers

B. Primary consumers

C. Decomposers

D. Top consumers

Answer: B

11. The third trophic level is generally occupied by:

A. Producers

B. Primary consumers

C. Secondary consumers

D. Decomposers

Answer: C

12. In Grass → Rabbit → Fox, fox is:

A. Producer

B. Primary consumer

C. Decomposer

D. Secondary consumer

Answer: D

13. Approximately what percentage of energy is transferred to the next trophic level according to the 10% law?

A. 10%

B. 25%

C. 50%

D. 90%

Answer: A

14. If producers contain 10,000 J, approximately how much may reach the next trophic level?

A. 10 J

B. 100 J

C. 1,000 J

D. 9,000 J

Answer: C

15. Energy flow in an ecosystem is generally:

A. Circular

B. Unidirectional

C. Random only

D. Completely reversible

Answer: B

16. Which statement is correct?

A. Food webs have only one feeding pathway

B. Food chains are always circular

C. Food webs contain interconnected feeding pathways

D. Trophic levels are abiotic factors

Answer: C

17. Which organism can occupy different trophic positions depending on its diet?

A. Omnivore

B. Producer only

C. Decomposer only

D. Sun

Answer: A

18. In Phytoplankton → Zooplankton → Fish, zooplankton is:

A. Producer

B. Primary consumer

C. Secondary consumer

D. Decomposer

Answer: B

19. Which organisms act on dead matter from different trophic levels?

A. Producers

B. Herbivores

C. Decomposers

D. Top predators

Answer: C

20. Why does energy decrease at higher trophic levels?

A. Energy is created at every level

B. All energy is stored permanently

C. Producers disappear

D. Much energy is used and eventually dissipated as heat

Answer: D

21. Which sequence represents increasing trophic level?

A. Producer → Primary → Secondary → Tertiary

B. Tertiary → Producer → Primary → Secondary

C. Secondary → Producer → Tertiary → Primary

D. Primary → Producer → Secondary → Tertiary

Answer: A

22. Which is NOT a food chain?

A. Grass → Rabbit → Fox

B. Grass → Deer → Tiger

C. Phytoplankton → Fish

D. Grass, rabbit, fox, snake as unrelated organisms

Answer: D

23. A food web is generally more complex because:

A. It has multiple interconnected food chains

B. It contains only producers

C. It excludes consumers

D. It contains no energy transfer

Answer: A

24. Which trophic level contains producers?

A. First

B. Second

C. Third

D. Fourth

Answer: A

25. If grass has 20,000 J, approximately how much may reach the primary consumers?

A. 2,000 J

B. 200 J

C. 20 J

D. 18,000 J

Answer: A

26. If 1,000 J reaches a primary consumer, approximately how much may reach the secondary consumer?

A. 1 J

B. 10 J

C. 100 J

D. 900 J

Answer: C

27. Which statement about nutrients is correct?

A. Nutrients can be recycled through ecosystem processes

B. Nutrients are always destroyed

C. Nutrients flow only from animals to sunlight

D. Nutrients are not required by producers

Answer: A

28. Which is an example of a food web relationship?

A. One animal eating only one food forever

B. Several animals sharing multiple food sources

C. Only sunlight reaching a plant

D. Only decomposition

Answer: B

29. Which factor helps explain why food chains usually contain limited trophic levels?

A. Energy transfer is inefficient

B. Producers eat top predators

C. Energy increases at every level

D. Decomposers stop all energy flow

Answer: A

30. Which statement is most accurate?

A. Food chain and food web mean exactly the same thing

B. Trophic level describes an organism's feeding position

C. Energy is completely recycled

D. Producers occupy the highest trophic level

Answer: B

28. Subjective Questions with Answers

2 Marks 1. Define food chain.

A food chain is a linear sequence of organisms through which food and energy are transferred as one organism eats another.

2 Marks 2. What is a trophic level?

A trophic level is the feeding position occupied by an organism in a food chain.

2 Marks 3. What is a food web?

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

2 Marks 4. What does an arrow in a food chain represent?

It represents the direction of food and energy transfer from the organism being eaten to the organism that eats it.

2 Marks 5. Name the first trophic level.

The first trophic level is occupied by producers.

3 Marks 6. Give one example of a food chain and identify its trophic levels.

Grass → Grasshopper → Frog → Snake. Grass is TL1, grasshopper TL2, frog TL3 and snake TL4.

3 Marks 7. Differentiate between food chain and food web.

A food chain is generally a single linear pathway, whereas a food web consists of several interconnected food chains and represents multiple feeding pathways.

3 Marks 8. What are primary consumers?

Primary consumers are organisms that feed directly on producers. They generally occupy the second trophic level and are usually herbivores.

3 Marks 9. Why is energy flow in an ecosystem unidirectional?

Energy enters mainly as sunlight, passes through producers and consumers, and is ultimately dissipated as heat. It is not recycled back in the same usable form.

4 Marks 10. Explain the different trophic levels.

The first trophic level consists of producers. The second consists generally of primary consumers. The third consists generally of secondary consumers. Higher trophic levels may contain tertiary or top consumers.

4 Marks 11. Explain the significance of the 10% law.

Approximately 10% of energy at one trophic level is transferred to the next. Consequently, energy decreases sharply at successive levels, limiting the number of trophic levels in many food chains.

4 Marks 12. Explain a grazing food chain with an example.

A grazing food chain begins with a living producer. Example: Grass → Grasshopper → Frog → Snake. Grass is the producer and the other organisms occupy successive consumer levels.

4 Marks 13. Why are food webs important?

Food webs show multiple feeding relationships. They provide alternative pathways for energy transfer and can contribute to stability because a consumer may have more than one food source.

5 Marks 14. Explain food chain with a suitable diagram.

A food chain represents a linear sequence of feeding relationships. Example: Grass → Grasshopper → Frog → Snake → Eagle. Grass is the producer, followed by primary, secondary and higher consumers. Arrows show the direction of food and energy transfer.

5 Marks 15. Explain food web with an example.

A food web consists of interconnected food chains. For example, grass may be eaten by rabbit, grasshopper and rat; these animals may be eaten by frogs, snakes, foxes and eagles. The interconnections form a food web.

5 Marks 16. Explain how energy decreases at successive trophic levels.

Only a fraction of the energy available at one trophic level is transferred to the next. According to the commonly taught 10% law, about 10% may be transferred. Much of the remaining energy is used in life processes and eventually dissipated as heat.

5 Marks 17. Explain the relationship between food chain and trophic levels.

A food chain shows the sequence of feeding relationships. Each position in that sequence represents a trophic level. Producers occupy TL1, primary consumers TL2, secondary consumers TL3 and higher consumers occupy subsequent levels.

5 Marks 18. Explain why a food web is more realistic than a single food chain for many ecosystems.

Most organisms eat more than one type of food and may themselves be eaten by several organisms. Therefore, actual feeding relationships form interconnected networks rather than a single simple pathway.

6 Marks 19. Explain food chain, food web and trophic levels together.

A food chain is a linear pathway of feeding. A food web is formed when several food chains become interconnected. Trophic level indicates an organism's feeding position. Producers are at TL1, primary consumers at TL2 and higher consumers occupy successive trophic levels.

6 Marks 20. Describe energy flow through a food chain.

Solar energy is captured by producers and converted into chemical energy. Primary consumers obtain energy by eating producers. Secondary and higher consumers obtain energy by eating other consumers. At each transfer, much energy is used and ultimately dissipated as heat, so available energy decreases.

6 Marks 21. Explain the 10% law using a numerical example.

If producers contain 10,000 J, approximately 1,000 J may reach primary consumers. About 100 J may reach secondary consumers and about 10 J may reach tertiary consumers. This illustrates the progressive decrease in available energy.

6 Marks 22. Explain why food chains generally have limited length.

Energy transfer between trophic levels is inefficient. Since only a small fraction is transferred to the next level, progressively less energy is available to support organisms at higher trophic levels.

6 Marks 23. How can a change in one species affect a food web?

Because organisms are interconnected, a change in one population can affect its prey, predators and competitors. For example, removal of a predator may allow some prey populations to increase, which can then affect their food resources.

6 Marks 24. Explain the importance of producers in a food chain.

Producers form the first trophic level and capture energy, mainly from sunlight. They convert it into chemical energy stored in organic food. This energy supports primary consumers and indirectly all higher trophic levels.

6 Marks 25. Explain the role of decomposers in relation to food chains.

Decomposers act on dead organisms and wastes from different trophic levels. They break down organic matter and help return nutrients to the environment, which can again become available to producers.

6 Marks 26. Explain the difference between energy flow and nutrient cycling.

Energy enters the ecosystem, flows through trophic levels and is eventually dissipated as heat. Nutrients, in contrast, can move between organisms and the environment and be recycled through processes such as decomposition.

6 Marks 27. Explain with an example how an omnivore can occupy different trophic positions.

If a human eats plants directly, the human acts as a primary consumer in that pathway. If the human eats an animal that feeds on plants, the human occupies a higher trophic position. Thus trophic position depends on the feeding pathway.

6 Marks 28. What happens to higher consumers if producers are severely reduced?

A reduction in producers reduces food and energy available to primary consumers. This can reduce populations of primary consumers and subsequently affect secondary and higher consumers through the interconnected food web.

6 Marks 29. Explain why food webs can contribute to ecosystem stability.

A food web provides several feeding pathways. If one food source becomes scarce, some consumers may use alternative sources. This flexibility can reduce the effect of a single disturbance, although severe disturbances can still affect the whole web.

6 Marks 30. Explain the complete sequence of energy transfer and nutrient recycling.

Sunlight is captured by producers and stored as chemical energy. Consumers obtain this energy through feeding. When organisms die or produce wastes, decomposers break down the organic matter and return nutrients to the environment. Producers use these nutrients again, while energy continues to flow and is eventually dissipated as heat.

29. Assertion–Reason Questions

1. Assertion: Producers occupy the first trophic level.
Reason: Producers capture energy and manufacture organic food.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

2. Assertion: A food web is generally more complex than a food chain.
Reason: A food web contains interconnected food chains.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

3. Assertion: Energy decreases at successive trophic levels.
Reason: Only a fraction of energy is transferred to the next trophic level.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

4. Assertion: Energy is completely recycled in an ecosystem.
Reason: Energy is eventually dissipated as heat.

Answer: Assertion is false, but Reason is true.

5. Assertion: Producers form the base of most food chains.
Reason: They introduce captured energy into the food chain.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

30. HOTS Questions

HOTS 1: Why does a food web generally represent an ecosystem better than one food chain?

Because organisms commonly have multiple food sources and multiple predators. A food web captures these interconnected relationships.

HOTS 2: If all frogs in a food web disappeared, what could happen?

Insect populations eaten by frogs might increase, while predators that depend on frogs might lose a food source. The exact effect depends on the whole food web.

HOTS 3: Why is energy available to an eagle less than energy available to grass in a food chain?

Energy is lost from the system as heat and used in life processes at each transfer. Therefore, progressively less energy is available at higher trophic levels.

HOTS 4: Why can the same organism occupy different trophic levels?

Its trophic position depends on what it eats and therefore on the particular food pathway being considered.

HOTS 5: Why would removal of producers have a larger ecosystem effect than removal of one individual consumer?

Producers form the base of energy input into most ecosystems. Their reduction can affect many consumers across multiple food chains and therefore the wider food web.

31. Quick Revision Table

Concept	Key Point
Food Chain	Linear feeding pathway.
Food Web	Interconnected food chains.
Trophic Level	Feeding position of an organism.
TL 1	Producers.
TL 2	Primary consumers.
TL 3	Secondary consumers.
TL 4	Tertiary consumers.
Energy Flow	Unidirectional.
10% Law	Approximately 10% transfer to next trophic level.
Decomposers	Break down dead matter and support nutrient recycling.

32. One-Minute Revision

🌱 Food Chain
Linear pathway of food and energy transfer.

🕸️ Food Web
Network of interconnected food chains.

1️⃣ First Trophic Level
Producers.

2️⃣ Second Trophic Level
Primary consumers.

3️⃣ Third Trophic Level
Secondary consumers.

4️⃣ Fourth Trophic Level
Tertiary/higher consumers in a suitable chain.

➡️ Arrow
Shows direction of food and energy transfer.

⚡ Energy
Flows in one direction and decreases at successive trophic levels.

♻️ Nutrients
Can be recycled through decomposition.

33. Golden Points for CBSE Exam

1. Food chain is generally a linear feeding pathway.

2. Food web consists of interconnected food chains.

3. Producers occupy the first trophic level.

4. Primary consumers generally occupy the second trophic level.

5. Secondary consumers generally occupy the third trophic level.

6. Tertiary consumers may occupy the fourth trophic level.

7. The arrow shows the direction of food/energy transfer.

8. Energy flow is unidirectional.

9. Approximately 10% energy transfer is used as the standard school-level 10% law.

10. Energy decreases at successive trophic levels.

11. Food webs provide multiple feeding pathways.

12. Decomposers act on dead organisms and wastes from different trophic levels.

13. Nutrients can be recycled.

14. A food web is more complex than a simple food chain.

15. Trophic position depends on the feeding relationship being considered.

34. MCQ Answer Key

Q	Ans	Q	Ans	Q	Ans
1	A	11	C	21	A
2	B	12	D	22	D
3	C	13	A	23	A
4	D	14	C	24	A
5	A	15	B	25	A
6	B	16	C	26	C
7	C	17	A	27	A
8	D	18	B	28	B
9	A	19	C	29	A
10	B	20	D	30	B

Our Environment and Sustainable Management
Food Chain • Food Web • Trophic Levels
Class 10 CBSE Science | Foundation | Competitive Preparation