Class 10th Science Chapter 13 – Our Environment | Trophic Levels and Energy Flow

🌍 Our Environment

Trophic Levels and Energy Flow | Class 10 Science | CBSE + Foundation + Competitive

🌍 Our Environment | Trophic Levels and Energy Flow

1. Introduction | परिचय

An ecosystem contains organisms occupying different positions in feeding relationships. These positions are called trophic levels. Energy enters most ecosystems through sunlight, is captured by producers, and then passes from one trophic level to another.

हिंदी: पारितंत्र में जीव खाद्य संबंधों के आधार पर अलग-अलग पोषण स्तरों पर पाए जाते हैं। इन पोषण स्तरों को Trophic Levels कहते हैं। अधिकांश पारितंत्रों में ऊर्जा का मुख्य प्रारंभिक स्रोत सूर्य है।

☀ Sun → 🌱 Producers → 🐇 Primary Consumers → 🐍 Secondary Consumers → 🦅 Higher Consumers

Core Idea: Energy flows through an ecosystem, while nutrients are recycled.

2. What is a Trophic Level? | पोषण स्तर क्या है?

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

Example:

Grass → Grasshopper → Frog → Snake

Grass = 1st trophic level
Grasshopper = 2nd trophic level
Frog = 3rd trophic level
Snake = 4th trophic level

3. Different Trophic Levels

Trophic Level	Organism Type	Example
1st	Producers	Grass, green plants
2nd	Primary Consumers / Herbivores	Grasshopper, deer, rabbit
3rd	Secondary Consumers	Frog, small carnivores
4th	Tertiary / Higher Consumers	Snake, eagle, large predators

Memory Trick:
🌱 Producer → Makes food
🐇 Primary Consumer → Eats producer
🐸 Secondary Consumer → Eats primary consumer
🦅 Higher Consumer → Eats lower consumers

4. First Trophic Level – Producers

Producers are organisms that prepare their own food, generally through photosynthesis.

Examples:
• Green plants
• Algae
• Phytoplankton

They form the first trophic level and are the main entry point of solar energy into most ecosystems.

Carbon dioxide + Water + Light Energy → Glucose + Oxygen

5. Second Trophic Level – Primary Consumers

Primary consumers generally feed directly on producers. They are commonly called herbivores.

Examples:
🌱 Grass → 🐇 Rabbit
🌱 Grass → 🦌 Deer
🌱 Plants → 🐛 Caterpillar

6. Third Trophic Level – Secondary Consumers

Secondary consumers generally feed on primary consumers.

Example:
Grass → Grasshopper → Frog

Here, the frog occupies the third trophic level.

7. Fourth Trophic Level – Higher Consumers

Higher-level consumers feed on organisms at lower trophic levels.

Example:
Grass → Grasshopper → Frog → Snake

Snake occupies the fourth trophic level in this particular chain.

8. Trophic Level Diagram | पोषण स्तर आरेख

9. What is Energy Flow? | ऊर्जा प्रवाह क्या है?

Energy flow is the transfer of energy from one trophic level to another through feeding relationships.

The basic sequence is:

Sun → Producers → Consumers

Unlike nutrients, energy is not continuously recycled within the ecosystem. It flows through the ecosystem and is eventually dissipated as heat.

10. Source of Energy in an Ecosystem

For most ecosystems, the ultimate source of energy is the Sun.

Green plants and other photosynthetic organisms capture a small fraction of solar energy and convert it into chemical energy stored in food.

That chemical energy becomes available to consumers through feeding.

11. Energy Flow Through a Food Chain

☀ Sun
↓
🌱 Grass – Producer
↓
🦗 Grasshopper – Primary Consumer
↓
🐸 Frog – Secondary Consumer
↓
🐍 Snake – Higher Consumer

At each step, organisms use a substantial portion of the energy they obtain for respiration, movement, growth, reproduction and maintenance. Therefore, only a fraction is available to the next trophic level.

12. Ten Percent Law | दस प्रतिशत नियम

The 10% law states that approximately 10% of the energy available at one trophic level is transferred to the next trophic level. This is the standard rule used in Class 10 ecology questions.

🌱 Producers = 10,000 J
↓ 10%
🐇 Primary Consumers = 1,000 J
↓ 10%
🐸 Secondary Consumers = 100 J
↓ 10%
🐍 Higher Consumers = 10 J

The 10% value is a simplified ecological rule for educational purposes. Actual transfer efficiency can vary among organisms and ecosystems.

13. Why Does Energy Decrease?

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

✔ Respiration
✔ Movement
✔ Growth
✔ Reproduction
✔ Repair and maintenance
✔ Other metabolic activities

A significant portion of energy is released as heat during metabolic processes.

14. Energy Pyramid

An energy pyramid represents the amount of energy available at different trophic levels. The base represents producers and contains the greatest amount of available energy.

15. Why is the Energy Pyramid Always Upright?

The energy pyramid is always upright because energy available at each successive trophic level is less than the energy available at the previous level.

Therefore:
Producer Energy > Primary Consumer Energy > Secondary Consumer Energy > Higher Consumer Energy

16. Energy Flow is Unidirectional

Energy flow through an ecosystem is generally unidirectional. It moves:

Sun → Producers → Consumers → Heat

Heat energy is not returned to the Sun or recycled back into usable chemical energy by the ecosystem.

Exam Statement: “Energy flows in one direction, whereas nutrients are recycled.”

17. Energy Flow vs Nutrient Cycling

Feature	Energy Flow	Nutrient Cycling
Nature	Unidirectional	Cyclic
Major source	Sun for most ecosystems	Environment/reservoirs
Recycling	Energy is not recycled as usable energy	Nutrients are recycled
Examples	Solar → Plants → Animals	Carbon, nitrogen, phosphorus cycles

18. Energy Loss at Each Trophic Level

Suppose producers contain 5000 J of available energy. Using the 10% rule:

Primary consumers receive approximately: 500 J

Secondary consumers receive approximately: 50 J

Tertiary consumers receive approximately: 5 J

19. Numerical Example – 1

Question: If producers contain 20,000 J of energy, how much energy is expected at the primary consumer level?

According to the 10% law:

Energy = 10% of 20,000
= 10/100 × 20,000
= 2,000 J

20. Numerical Example – 2

Question: If producers contain 50,000 J, estimate the energy available at the tertiary consumer level.

Producer = 50,000 J
Primary consumer = 5,000 J
Secondary consumer = 500 J
Tertiary consumer = 50 J

21. Effect of a Long Food Chain

As the number of trophic levels increases, the amount of energy available at the highest level becomes progressively smaller. Therefore, long food chains generally support fewer organisms at their highest trophic levels than producers at the base.

22. Why Are Producers Important?

Producers are the foundation of most food chains because they convert solar energy into chemical energy stored in organic food. Without sufficient producers, less energy would enter the ecosystem and fewer consumers could be supported.

23. Role of Decomposers

Decomposers break down dead organic matter and return nutrients to the environment. They are essential for nutrient recycling but should not be treated simply as another higher trophic level in every food-chain diagram.

Important distinction: Energy flows through the ecosystem, whereas matter/nutrients can be recycled.

24. 30 MCQs | Multiple Choice Questions

1. The first trophic level consists of:

A. Producers

B. Primary consumers

C. Secondary consumers

D. Decomposers

Answer: A

2. The second trophic level generally contains:

A. Producers

B. Primary consumers

C. Secondary consumers

D. Decomposers

Answer: B

3. The ultimate energy source for most ecosystems is:

A. Soil

B. Moon

C. Sun

D. Wind

Answer: C

4. A trophic level represents:

A. Position in a feeding relationship

B. Amount of rainfall

C. Soil depth

D. Temperature

Answer: A

5. In Grass → Deer → Tiger, deer belongs to:

A. First trophic level

B. Second trophic level

C. Third trophic level

D. Fourth trophic level

Answer: B

6. In Grass → Grasshopper → Frog, frog belongs to:

A. First trophic level

B. Second trophic level

C. Third trophic level

D. Fourth trophic level

Answer: C

7. The energy pyramid is generally:

A. Always inverted

B. Always upright

C. Circular

D. Horizontal

Answer: B

8. Approximately what percentage of energy is transferred to the next trophic level?

A. 10%

B. 25%

C. 50%

D. 90%

Answer: A

9. Energy flow in an ecosystem is:

A. Unidirectional

B. Completely cyclic

C. Random

D. Reversible

Answer: A

10. Which organism captures solar energy?

A. Tiger

B. Snake

C. Green plant

D. Eagle

Answer: C

11. Energy decreases at successive trophic levels mainly because:

A. Energy is used in life processes and dissipated as heat

B. Producers disappear

C. Consumers stop feeding

D. Sunlight becomes weaker

Answer: A

12. If producers contain 1000 J, primary consumers may receive approximately:

A. 100 J

B. 500 J

C. 900 J

D. 10 J

Answer: A

13. If primary consumers have 200 J, approximately how much may reach secondary consumers?

A. 200 J

B. 100 J

C. 20 J

D. 2 J

Answer: C

14. Which has maximum available energy in a simple energy pyramid?

A. Producers

B. Secondary consumers

C. Tertiary consumers

D. Top predators

Answer: A

15. Nutrients in an ecosystem are generally:

A. Destroyed completely

B. Recycled

C. Converted only into sunlight

D. Never reused

Answer: B

16. Which statement is correct?

A. Energy is recycled endlessly

B. Energy flows and nutrients cycle

C. Nutrients flow only one way

D. Both are identical processes

Answer: B

17. A primary consumer is usually:

A. Herbivore

B. Producer

C. Decomposer

D. Top carnivore

Answer: A

18. Which is an example of a producer?

A. Grass

B. Frog

C. Snake

D. Eagle

Answer: A

19. Energy used by organisms for respiration is eventually largely:

A. Stored forever

B. Released as heat

C. Converted into soil

D. Returned directly to sunlight

Answer: B

20. Which trophic level has the least energy in a simple chain?

A. Producer

B. Primary consumer

C. Secondary consumer

D. Highest consumer

Answer: D

21. If producers contain 5000 J, the primary consumer level may contain:

A. 50 J

B. 500 J

C. 2500 J

D. 4500 J

Answer: B

22. If 1000 J reaches primary consumers, approximately how much reaches secondary consumers?

A. 100 J

B. 500 J

C. 10 J

D. 900 J

Answer: A

23. The energy pyramid represents:

A. Energy available at trophic levels

B. Only number of species

C. Only rainfall

D. Only temperature

Answer: A

24. Why is the base of an energy pyramid broad?

A. Producers contain maximum available energy

B. Top predators are most numerous

C. Heat increases upward

D. Decomposers are absent

Answer: A

25. Which process introduces energy into most ecosystems?

A. Photosynthesis

B. Decomposition

C. Predation

D. Excretion

Answer: A

26. Energy flow is different from nutrient cycling because:

A. Energy is generally not recycled as usable energy

B. Nutrients are never recycled

C. Energy is always cyclic

D. Both are identical

Answer: A

27. Which sequence is correct?

A. Sun → Producers → Consumers

B. Consumers → Sun → Producers

C. Producers → Sun → Consumers

D. Consumers → Producers → Sun

Answer: A

28. A longer food chain generally has:

A. More energy at the top

B. Less energy available at the highest trophic level

C. No energy loss

D. Equal energy at all levels

Answer: B

29. Which organisms form the foundation of most terrestrial food chains?

A. Green plants

B. Tigers

C. Snakes

D. Eagles

Answer: A

30. The 10% law is related to:

A. Transfer of energy between trophic levels

B. Transfer of water between clouds

C. Soil formation

D. Reproduction

Answer: A

25. 30 Subjective Questions with Answers

2 Marks Q1. What is a trophic level?

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

2 Marks Q2. Name the first trophic level.

The first trophic level is occupied by producers such as green plants.

2 Marks Q3. What is energy flow?

Energy flow is the transfer of energy from one trophic level to another through feeding relationships.

2 Marks Q4. What is the main source of energy for most ecosystems?

The Sun is the main source of energy for most ecosystems.

2 Marks Q5. State the 10% law.

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

3 Marks Q6. Name the first four trophic levels.

1. Producers
2. Primary consumers
3. Secondary consumers
4. Tertiary/higher consumers

3 Marks Q7. Why are producers placed at the first trophic level?

Producers prepare their own food and capture solar energy. They form the primary entry point of energy into most ecosystems.

3 Marks Q8. Why does energy decrease at successive trophic levels?

Organisms use energy for respiration, movement, growth and other life processes. Much energy is dissipated as heat, leaving less for the next level.

3 Marks Q9. What is meant by unidirectional energy flow?

Energy moves in one general direction from the Sun to producers, then to consumers and finally is dissipated as heat.

3 Marks Q10. Differentiate between energy flow and nutrient cycling.

Energy flows through an ecosystem and is ultimately dissipated as heat, whereas nutrients such as carbon and nitrogen are recycled between organisms and the environment.

4 Marks Q11. Explain the different trophic levels with an example.

In Grass → Grasshopper → Frog → Snake, grass is the producer at the first trophic level, grasshopper is the primary consumer at the second, frog is the secondary consumer at the third and snake occupies the fourth trophic level.

4 Marks Q12. Explain why producers are essential for energy flow.

Producers capture solar energy and convert it into chemical energy stored in food. Consumers obtain this energy directly or indirectly by feeding on producers or other consumers.

4 Marks Q13. Why is the energy pyramid always upright?

Energy available decreases at each successive trophic level. Therefore, producers have the greatest energy and higher trophic levels have progressively less energy.

4 Marks Q14. Explain the importance of the 10% law.

It explains why energy decreases sharply along a food chain and why higher trophic levels receive much less energy than producers.

4 Marks Q15. What happens to energy obtained by an organism?

Energy is used for metabolic activities such as respiration, movement, growth and reproduction. Much of it is dissipated as heat, while only a fraction becomes available to the next trophic level.

5 Marks Q16. Explain energy flow in an ecosystem.

Solar energy is captured by producers and converted into chemical energy. This energy passes to primary consumers, secondary consumers and higher consumers through feeding. At every trophic transfer, much energy is used for life processes and dissipated as heat. Hence, energy flow is unidirectional.

5 Marks Q17. Explain the 10% law with a numerical example.

If producers contain 10,000 J, primary consumers may receive about 1,000 J. Secondary consumers may receive about 100 J and tertiary consumers about 10 J. Thus approximately 10% passes to each successive trophic level.

5 Marks Q18. Why does a food chain usually contain only a few trophic levels?

Energy decreases greatly at each trophic transfer. After several transfers, very little energy remains to support another trophic level. Therefore, food chains are generally relatively short.

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

A food chain shows feeding relationships, while energy flow describes the transfer of energy through those feeding relationships. Energy enters through producers and passes through successive consumers.

5 Marks Q20. Why is sunlight important for most ecosystems?

Sunlight provides the energy captured by photosynthetic producers. This energy is converted into chemical energy and becomes available to consumers through food chains.

6 Marks Q21. Explain trophic levels and energy transfer in detail.

Trophic levels represent feeding positions in a food chain. Producers occupy the first level, herbivores the second, secondary consumers the third and higher consumers subsequent levels. Energy enters through producers and passes upward. Only a small fraction, approximately 10% as a textbook rule, reaches each next level. The remaining energy is used in life processes or dissipated as heat.

6 Marks Q22. Explain why energy flow is unidirectional.

Energy enters most ecosystems from the Sun, is captured by producers, passes through consumers and is eventually dissipated as heat. Heat cannot be converted back into the original usable chemical energy by the ecosystem in a continuous cycle. Therefore energy flow is unidirectional.

6 Marks Q23. Explain the energy pyramid.

An energy pyramid shows the energy available at different trophic levels. Producers form the broad base because they contain the greatest amount of available energy. Higher trophic levels contain progressively less energy because only a fraction of energy is transferred at each step.

6 Marks Q24. Explain the difference between energy flow and nutrient cycling.

Energy enters mainly as solar energy and flows through trophic levels before being dissipated as heat. Nutrients, however, move between organisms and the physical environment and are recycled through processes such as decomposition and biogeochemical cycles.

6 Marks Q25. Why does the amount of energy available to top consumers become very small?

At each trophic level, organisms use energy for respiration, movement, growth, reproduction and maintenance. A substantial amount is dissipated as heat. Consequently, only a small fraction is passed to the next level, making the energy available to top consumers very small.

6 Marks Q26. A food chain contains 40,000 J at the producer level. Calculate approximate energy at the next three trophic levels.

Producer = 40,000 J
Primary consumer = 4,000 J
Secondary consumer = 400 J
Tertiary consumer = 40 J

Thus the approximate energies are 4,000 J, 400 J and 40 J.

6 Marks Q27. Explain why producers are called the foundation of an ecosystem.

Producers capture energy and manufacture organic food. This stored chemical energy becomes available to herbivores and subsequently to higher consumers. Therefore, producers form the energetic foundation of most ecosystems.

6 Marks Q28. Explain the role of decomposers in relation to energy and nutrients.

Decomposers obtain energy by breaking down dead organic matter. During their metabolism, energy is also dissipated as heat. At the same time, decomposition releases nutrients back into the environment, making them available for reuse by producers.

6 Marks Q29. Why can higher trophic levels support fewer organisms in many ecosystems?

Higher trophic levels receive less energy because energy is lost during every transfer. The limited energy available at higher levels restricts the biomass and number of organisms that can generally be supported.

6 Marks Q30. Write a complete note on trophic levels and energy flow.

Trophic levels are feeding positions in an ecosystem. Producers occupy the first level, followed by primary, secondary and higher consumers. Energy enters through producers, mainly from sunlight, and moves through successive trophic levels. Approximately 10% of available energy is transferred to the next level according to the standard 10% law. The rest is largely used for life processes or dissipated as heat. Thus energy flow is unidirectional, while nutrients are recycled.

26. Assertion–Reason Questions

Assertion (A): Producers occupy the first trophic level.
Reason (R): Producers capture energy and prepare food.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Energy available decreases at successive trophic levels.
Reason (R): Organisms use energy for life processes and much energy is dissipated as heat.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Energy flow in an ecosystem is cyclic.
Reason (R): Energy is continuously recycled between trophic levels.

Answer: Both A and R are false.

Assertion (A): The energy pyramid is generally upright.
Reason (R): Available energy decreases at successive trophic levels.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Nutrients and energy behave identically in an ecosystem.
Reason (R): Nutrients are recycled whereas energy flows through the ecosystem and is eventually dissipated as heat.

Answer: Assertion is false, but Reason is true.

27. HOTS | Higher Order Thinking

HOTS 1: If producers contain 30,000 J, estimate the energy available at the tertiary consumer level.

30,000 → 3,000 → 300 → 30 J.

HOTS 2: Why would a sudden decline in producers affect higher trophic levels?

Producers are the main entry point of energy into most ecosystems. Their decline reduces food and energy available to primary consumers and consequently to higher consumers.

HOTS 3: Why are food chains generally short?

Because only a fraction of energy is transferred to each successive trophic level, the available energy becomes too small to support many additional levels.

HOTS 4: Why is the energy pyramid different from a biomass pyramid in some ecosystems?

An energy pyramid measures energy available at trophic levels and is always upright. Biomass represents the mass of living material and can have different shapes depending on the ecosystem.

HOTS 5: Why can nutrients be reused but energy cannot be recycled in the same way?

Nutrients are matter and can move repeatedly between organisms and the environment. Energy is transformed during metabolic processes and much is dissipated as heat, so it does not continuously return as usable energy.

28. Important Diagrams to Practise

Diagram 1: Trophic pyramid

Higher Consumers
↑
Secondary Consumers
↑
Primary Consumers
↑
Producers

Diagram 2: Energy flow

☀ Sun → 🌱 Producers → 🐇 Herbivores → 🐍 Carnivores → Heat

Diagram 3: Ten Percent Law

1000 J → 100 J → 10 J → 1 J

29. Golden Points | परीक्षा के लिए महत्वपूर्ण

✔ Trophic level = feeding position in a food chain.

✔ Producers = first trophic level.

✔ Primary consumers = second trophic level.

✔ Secondary consumers = third trophic level.

✔ Higher consumers occupy subsequent trophic levels.

✔ Sun is the major energy source for most ecosystems.

✔ Energy flow is unidirectional.

✔ Energy decreases at successive trophic levels.

✔ Approximately 10% energy is transferred to the next trophic level.

✔ Energy pyramid is always upright.

✔ Nutrients are recycled.

✔ Energy is ultimately dissipated as heat.

30. One-Minute Revision

Trophic Level → Position in food chain

1st Level → Producers

2nd Level → Primary Consumers

3rd Level → Secondary Consumers

Higher Levels → Higher Consumers

Energy Source → Sun

Energy Flow → Unidirectional

10% Law → About 10% transfers upward

Energy Pyramid → Always upright

Nutrients → Recycled

31. Concept Map | अवधारणा मानचित्र

32. Final Summary

Trophic levels describe the feeding positions of organisms in an ecosystem.

The first trophic level contains producers, followed by primary consumers, secondary consumers and higher consumers.

For most ecosystems, energy enters through the Sun and is captured by producers.

Energy then moves through consumers. At every trophic transfer, much energy is used in life processes and dissipated as heat.

According to the standard 10% law, approximately 10% of the energy available at one trophic level reaches the next trophic level.

Therefore, the energy pyramid is always upright and energy flow is generally unidirectional.

Remember:

☀ Sun → 🌱 Producers → 🐇 Primary Consumers → 🐸 Secondary Consumers → 🦅 Higher Consumers

Energy flows; nutrients cycle.

🌍 Class 10 Science | Our Environment

Trophic Levels • Energy Flow • 10% Law • Energy Pyramid • Food Chain • Nutrient Cycling

CBSE + Foundation + Competitive Preparation

Class 10th Science Chapter 13 – Our Environment | Food Chain and Food Web

🌍 Our Environment

Food Chain and Food Web | Class 10 Science | CBSE + Foundation + Competitive

🌍 Our Environment | Food Chain and Food Web

1. Introduction | परिचय

A food chain shows a linear sequence of organisms through which food and energy pass as one organism eats another.

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

हिंदी: खाद्य श्रृंखला जीवों की एक क्रमिक श्रृंखला है जिसमें एक जीव दूसरे जीव को खाता है और भोजन तथा ऊर्जा का स्थानांतरण होता है। अनेक खाद्य श्रृंखलाएँ आपस में जुड़कर खाद्य जाल बनाती हैं।

☀ Sun → 🌱 Producer → 🐇 Primary Consumer → 🐸 Secondary Consumer → 🐍 Higher Consumer

Exam Point: A food chain mainly represents a single feeding pathway, whereas a food web represents several interconnected feeding pathways.

2. What is a Food Chain? | खाद्य श्रृंखला क्या है?

Definition: A food chain is a sequence of organisms in which each organism serves as food for the next organism.

Example:
Grass → Grasshopper → Frog → Snake → Eagle

In this chain:

🌱 Grass = Producer
🦗 Grasshopper = Primary Consumer
🐸 Frog = Secondary Consumer
🐍 Snake = Higher Consumer
🦅 Eagle = Higher-level consumer

3. Main Components of a Food Chain

Component	Role	Example
Producer	Prepares food and captures energy	Grass
Primary Consumer	Feeds directly on producer	Grasshopper
Secondary Consumer	Feeds on primary consumer	Frog
Higher Consumer	Feeds on lower consumers	Snake/Eagle
Decomposer	Breaks down dead organic matter	Bacteria/Fungi

4. Trophic Levels | पोषण स्तर

Each step or position in a food chain is called a trophic level.

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

Remember:
1st Trophic Level → Producer
2nd → Primary Consumer
3rd → Secondary Consumer
4th → Tertiary Consumer

5. Food Chain Diagram | खाद्य श्रृंखला

6. Direction of Arrow in a Food Chain

The arrow in a food chain represents the movement of food and energy from the organism being eaten to the organism that eats it.

Example:
Grass → Deer

The arrow points from grass to deer because deer obtains food and energy by eating grass.

Important: The arrow does not mean that the predator physically moves toward the prey. It represents transfer of food/energy.

7. Types of Food Chains | खाद्य श्रृंखला के प्रकार

1. Grazing Food Chain
Begins with living green plants.

Example:
Grass → Deer → Tiger

2. Detritus Food Chain
Begins with dead organic matter or detritus and involves decomposers/detritivores.

Example:
Dead leaves → Detritivores → Predators

8. Grazing Food Chain | चराई खाद्य श्रृंखला

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

Example:
Grass → Grasshopper → Frog → Snake → Eagle

Most textbook examples of simple food chains begin with a producer and then proceed through consumers.

9. Detritus Food Chain | डेट्रिटस खाद्य श्रृंखला

A detritus food chain starts with dead organic matter such as fallen leaves and dead plant material.

Example:
Dead Leaves → Earthworm/Detritivore → Bird

Decomposers such as fungi and bacteria play an important role in decomposition and nutrient recycling associated with dead organic matter.

10. What is a Food Web? | खाद्य जाल क्या है?

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

हिंदी: किसी पारितंत्र में अनेक खाद्य श्रृंखलाओं के आपस में जुड़ने से बनने वाले नेटवर्क को खाद्य जाल (Food Web) कहते हैं।

Multiple Food Chains → Interconnected Network → Food Web

11. Food Web Diagram | खाद्य जाल

12. Food Chain vs Food Web

Feature	Food Chain	Food Web
Structure	Linear sequence	Network of interconnected chains
Feeding pathways	Usually one main pathway	Multiple pathways
Complexity	Relatively simple	More complex
Stability	Generally more vulnerable to disruption	Often provides alternative feeding pathways
Example	Grass → Deer → Tiger	Multiple chains connected through shared organisms

13. Why is a Food Web More Realistic?

In nature, organisms usually do not depend on only one food source. An organism may eat several types of food and may itself be eaten by several predators. Therefore, actual ecosystems are better represented by food webs rather than isolated food chains.

14. Interdependence in a Food Web

Suppose a food web contains:

Grass → Rabbit → Fox
Grass → Grasshopper → Frog → Snake → Eagle
Grass → Mouse → Snake → Eagle

Here, several organisms participate in more than one feeding relationship.

15. What Happens if One Organism Decreases?

A change in the population of one organism can affect several other organisms connected to it.

For example, if the population of grass decreases:
• Herbivores may have less food.
• Herbivore populations may decline.
• Predators may then have fewer prey.
• Several connected feeding relationships may be affected.

16. What Happens if a Predator is Removed?

Removal of a predator can increase the population of its prey. Increased prey populations may then consume more producers. This can create changes at multiple trophic levels.

This type of indirect effect shows why organisms in a food web are interdependent.

17. Energy Flow Through a Food Chain

☀ Sun
↓
🌱 Producers
↓
🐇 Primary Consumers
↓
🐍 Secondary/Higher Consumers

Energy enters most ecosystems through producers. At each trophic transfer, only a fraction of the available energy reaches the next trophic level.

18. Ten Percent Law | दस प्रतिशत नियम

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

Producer = 1000 J
↓
Primary Consumer ≈ 100 J
↓
Secondary Consumer ≈ 10 J
↓
Tertiary Consumer ≈ 1 J

The 10% figure is a useful ecological rule taught at this level; actual energy transfer efficiencies vary among ecosystems and organisms.

19. Food Chain and Decomposers

When organisms die, their remains become dead organic matter. Decomposers such as bacteria and fungi break down this material and return nutrients to the environment.

Thus, decomposers are connected with every trophic level because organisms from different levels eventually contribute dead organic matter.

Living Organisms
↓
Dead Organic Matter
↓
Decomposers
↓
Nutrients
↓
Environment / Producers

20. Food Chain and Food Web – Important Terms

Term	Meaning
Food Chain	Linear feeding sequence
Food Web	Interconnected food chains
Trophic Level	Position of an organism in a food chain
Producer	Organism that generally makes its own food
Primary Consumer	Feeds directly on producers
Secondary Consumer	Feeds mainly on primary consumers
Decomposer	Breaks down dead organic matter
Energy Flow	Transfer of energy through trophic levels

21. 30 MCQs | Multiple Choice Questions

1. A food chain represents:

A. A linear feeding relationship

B. Only decomposition

C. Only water movement

D. Only population growth

Answer: A

2. Which is the correct food chain?

A. Tiger → Grass → Deer

B. Grass → Deer → Tiger

C. Deer → Grass → Tiger

D. Tiger → Deer → Grass

Answer: B

3. The first trophic level is occupied by:

A. Primary consumers

B. Secondary consumers

C. Producers

D. Decomposers

Answer: C

4. A food web is:

A. A single organism

B. A network of interconnected food chains

C. A water cycle

D. A single food chain only

Answer: B

5. In Grass → Deer → Tiger, deer is:

A. Producer

B. Primary consumer

C. Secondary consumer

D. Decomposer

Answer: B

6. In Grass → Grasshopper → Frog, frog is:

A. Producer

B. Primary consumer

C. Secondary consumer

D. Decomposer

Answer: C

7. The arrow in a food chain generally represents:

A. Movement of soil

B. Direction of food and energy transfer

C. Direction of wind

D. Movement of water

Answer: B

8. Which is a producer?

A. Grass

B. Frog

C. Snake

D. Eagle

Answer: A

9. A food web contains:

A. One feeding pathway only

B. Several interconnected feeding pathways

C. Only producers

D. Only decomposers

Answer: B

10. Which food chain starts with a producer?

A. Tiger → Deer → Grass

B. Grass → Rabbit → Fox

C. Snake → Frog → Grass

D. Eagle → Snake → Frog

Answer: B

11. A food chain generally shows:

A. Feeding relationships

B. Only reproduction

C. Only respiration

D. Only decomposition

Answer: A

12. Which term describes the position of an organism in a food chain?

A. Habitat

B. Trophic level

C. Population

D. Community

Answer: B

13. Which is generally more complex?

A. Food chain

B. Food web

C. Single organism

D. Producer only

Answer: B

14. Grass → Grasshopper → Frog → Snake contains how many trophic levels?

A. 2

B. 3

C. 4

D. 5

Answer: C

15. The energy entering most ecosystems initially comes from:

A. Moon

B. Sun

C. Soil

D. Decomposers

Answer: B

16. Approximately what fraction of energy is transferred to the next trophic level?

A. 10%

B. 25%

C. 50%

D. 90%

Answer: A

17. A grazing food chain starts with:

A. Dead matter

B. Living producers

C. Decomposers

D. Carnivores

Answer: B

18. A detritus food chain starts with:

A. Living tiger

B. Green grass only

C. Dead organic matter

D. Sunlight only

Answer: C

19. Which organisms are important decomposers?

A. Bacteria and fungi

B. Deer and rabbit

C. Tiger and lion

D. Grass and algae

Answer: A

20. Which statement is correct?

A. Food webs have only one feeding pathway

B. Food chains can form part of food webs

C. Food chains contain no consumers

D. Food webs contain no producers

Answer: B

21. If grass decreases greatly, which organisms may be directly affected?

A. Herbivores

B. Sun

C. Soil minerals only

D. Clouds

Answer: A

22. Removal of a predator may initially cause:

A. An increase in some prey populations

B. Immediate disappearance of producers

C. No ecological effect ever

D. Creation of sunlight

Answer: A

23. Which is an example of a food web component?

A. An organism participating in several feeding relationships

B. Only sunlight

C. Only soil

D. Only rainfall

Answer: A

24. Energy flow in an ecosystem is generally:

A. Cyclic

B. Unidirectional

C. Random only

D. Completely reversible

Answer: B

25. Which sequence shows correct energy transfer?

A. Tiger → Grass → Sun

B. Sun → Grass → Deer

C. Deer → Grass → Sun

D. Snake → Frog → Grass

Answer: B

26. The main difference between a food chain and a food web is:

A. Food chain is linear; food web is interconnected

B. Food chain has no producers

C. Food web has no consumers

D. Both are exactly identical

Answer: A

27. Which organism can occur in more than one food chain?

A. A consumer with multiple food sources

B. Only the Sun

C. Only soil

D. No organism

Answer: A

28. Nutrients from dead organisms are returned to the environment mainly through:

A. Decomposition

B. Predation only

C. Photosynthesis only

D. Transpiration only

Answer: A

29. A food web generally makes an ecosystem:

A. More interconnected

B. Completely independent

C. Free from all changes

D. Without producers

Answer: A

30. Which statement is most appropriate?

A. A food chain represents one main feeding pathway

B. A food web contains only one organism

C. Energy increases at every trophic level

D. Decomposers are unrelated to food webs

Answer: A

22. 30 Subjective Questions with Answers

2 Marks Q1. What is a food chain?

A food chain is a linear sequence of organisms in which food and energy pass from one organism to another through feeding.

2 Marks Q2. What is a food web?

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

2 Marks Q3. What is a trophic level?

The position occupied by an organism in a food chain is called its trophic level.

2 Marks Q4. Give one example of a food chain.

Grass → Deer → Tiger.

2 Marks Q5. What does an arrow in a food chain indicate?

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

3 Marks Q6. Differentiate between food chain and food web.

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

3 Marks Q7. What are trophic levels? Give their sequence.

Trophic levels are positions in a food chain. The usual sequence is producer → primary consumer → secondary consumer → tertiary/higher consumer.

3 Marks Q8. Why is grass placed at the beginning of the food chain Grass → Deer → Tiger?

Grass is a producer. It captures solar energy and prepares food. Deer obtains food from grass and tiger obtains food from deer.

3 Marks Q9. What is a grazing food chain?

A grazing food chain begins with living green producers and proceeds through herbivores and higher consumers.

3 Marks Q10. What is a detritus food chain?

A detritus food chain begins with dead organic matter such as fallen leaves and involves organisms that feed on or decompose this material.

4 Marks Q11. Explain the importance of food chains in an ecosystem.

Food chains show feeding relationships, transfer of energy between organisms and the sequence of trophic levels. They help us understand how organisms depend on one another.

4 Marks Q12. Explain the importance of food webs.

Food webs represent multiple feeding relationships. They show the interdependence of organisms and provide a more realistic representation of feeding interactions in an ecosystem.

4 Marks Q13. Explain the role of decomposers in a food web.

Decomposers break down dead organisms and organic wastes from different trophic levels. They return nutrients to the environment and therefore support nutrient cycling.

4 Marks Q14. Explain the four trophic levels of a simple food chain.

The first level contains producers. The second contains primary consumers. The third contains secondary consumers. The fourth may contain tertiary or higher consumers.

4 Marks Q15. Why are food webs generally more realistic than simple food chains?

Organisms generally have more than one food source and may have several predators. Therefore, feeding relationships in nature are interconnected rather than strictly linear.

5 Marks Q16. Explain the flow of energy through a food chain.

Energy enters most ecosystems through sunlight captured by producers. It passes to primary consumers, then to secondary and higher consumers. At each trophic transfer, much of the energy is used in life processes and dissipated as heat, so only a fraction reaches the next level.

5 Marks Q17. Explain the ten percent law.

The ten percent law states that approximately 10% of the energy available at one trophic level is transferred to the next trophic level. For example, 1000 J at the producer level may provide about 100 J to primary consumers and about 10 J to secondary consumers.

5 Marks Q18. Explain how a food web is formed.

Different food chains in an ecosystem share organisms. When these chains intersect through common producers or consumers, they form an interconnected network called a food web.

5 Marks Q19. Explain the effect of removing one species from a food web.

Removing one species can affect organisms that depend on it for food and organisms that it normally consumes. Because a food web contains interconnected relationships, the effect may spread to several trophic levels.

5 Marks Q20. Differentiate between grazing and detritus food chains.

A grazing food chain begins with living producers such as green plants. A detritus food chain begins with dead organic matter such as fallen leaves. The two chains therefore differ in their starting material.

6 Marks Q21. Explain food chain, trophic levels and energy flow together.

A food chain represents a sequence of organisms linked through feeding. Each position is called a trophic level, beginning with producers. Energy enters through producers and passes to consumers. The available energy decreases at successive trophic levels because organisms use energy for life processes and much is dissipated as heat.

6 Marks Q22. Describe a food web with a suitable example.

A food web consists of several interconnected food chains. For example, grass may be eaten by grasshoppers, rabbits and mice. Grasshoppers may be eaten by frogs, mice by snakes and rabbits by foxes. Snakes may be eaten by eagles. Such interconnected feeding relationships form a food web.

6 Marks Q23. Explain why food webs increase interdependence among organisms.

In a food web, one organism may have several food sources and several predators. Therefore, a change in one population can influence multiple other populations. This creates a network of interdependence.

6 Marks Q24. Explain the role of decomposers in maintaining an ecosystem.

Decomposers break down dead organisms and organic wastes. They convert complex organic matter into simpler substances and release nutrients back into the environment. These nutrients can then be used by producers, maintaining nutrient cycling.

6 Marks Q25. Why does energy decrease at successive trophic levels?

Organisms use energy for respiration, movement, growth, maintenance and other life processes. A significant part of energy is dissipated as heat. Consequently, only a fraction of energy is available for transfer to the next trophic level.

6 Marks Q26. Explain what may happen if producers decline sharply in an ecosystem.

Primary consumers would have less food and their population could decline. Secondary and higher consumers would subsequently face reduced prey availability. Energy entering the food web would also decrease, disturbing the ecosystem.

6 Marks Q27. Explain why arrows in a food chain are important.

Arrows show the direction in which food and energy are transferred. For example, Grass → Deer means deer obtains food and energy by feeding on grass. Thus arrows help identify feeding relationships and trophic direction.

6 Marks Q28. Explain the difference between energy flow and nutrient cycling.

Energy enters an ecosystem mainly through sunlight and flows through trophic levels, with energy ultimately dissipated as heat. Nutrients are recycled between organisms and the physical environment through processes such as decomposition.

6 Marks Q29. Why can a food web provide greater ecological stability than a simple food chain?

A food web provides alternative feeding pathways. If one food source becomes unavailable, some consumers may use another available food source. This can reduce the impact of a single change, although food webs can still be significantly disturbed.

6 Marks Q30. Write a detailed note on food chains and food webs.

A food chain is a linear sequence of organisms through which food and energy pass. It starts with a producer and continues through different consumers. Each position is a trophic level. A food web consists of interconnected food chains and represents the more complex feeding relationships found in natural ecosystems. Decomposers act on dead organic matter and recycle nutrients. Energy flows through the system, while nutrients are recycled.

23. Assertion–Reason Questions

Assertion (A): A food web consists of several interconnected food chains.
Reason (R): Organisms in an ecosystem may have more than one food source and more than one predator.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Producers occupy the first trophic level.
Reason (R): Producers capture energy and prepare food.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): The arrow Grass → Deer indicates energy transfer from deer to grass.
Reason (R): Arrows in food chains point from the food organism to the organism that obtains it.

Answer: Assertion is false, but Reason is true.

Assertion (A): Energy decreases at successive trophic levels.
Reason (R): Organisms use energy for life processes and much energy is dissipated as heat.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Food webs are generally more complex than food chains.
Reason (R): A food web contains multiple interconnected feeding pathways.

Answer: Both A and R are true, and R correctly explains A.

24. HOTS | Higher Order Thinking Questions

HOTS 1: Why can removal of one species affect several other species in a food web?

Because one species may serve as food for several organisms and may also consume several organisms. Its removal can therefore alter multiple feeding relationships.

HOTS 2: If grasshoppers suddenly decrease in number, what may happen to frogs?

Frogs that depend significantly on grasshoppers as prey may face reduced food availability, potentially affecting their population.

HOTS 3: Why is a food web less likely than a single food chain to be completely dependent on one feeding pathway?

A food web contains multiple feeding pathways. Some organisms may have alternative food sources, so one disrupted pathway may not eliminate all available feeding options.

HOTS 4: Why are long food chains generally less efficient in energy transfer?

Only a fraction of energy passes to each successive trophic level. Therefore, available energy becomes progressively smaller along a longer chain.

HOTS 5: Why are top consumers usually fewer in number than producers in an ecosystem?

Energy available decreases at successive trophic levels. Less energy is available to support organisms at higher trophic levels, limiting their biomass and population size in many ecosystems.

25. Important Exam Diagrams

Diagram 1 – Simple Food Chain

☀ Sun → 🌱 Grass → 🦌 Deer → 🐅 Tiger

Diagram 2 – Food Web

Grass → Grasshopper → Frog → Snake → Eagle
Grass → Rabbit → Fox
Grass → Mouse → Snake

Diagram 3 – Trophic Levels

Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer

26. Golden Points | परीक्षा के लिए महत्वपूर्ण

✔ Food chain = linear feeding pathway.

✔ Food web = interconnected food chains.

✔ Producers occupy the first trophic level.

✔ Primary consumers generally feed on producers.

✔ Secondary consumers generally feed on primary consumers.

✔ Arrows show direction of food and energy transfer.

✔ Energy flow is generally unidirectional.

✔ Only about 10% of energy is transferred to the next trophic level as a textbook rule.

✔ Food webs show greater complexity and interdependence.

✔ Decomposers recycle nutrients from dead organic matter.

27. One-Minute Revision

Food Chain → One main feeding pathway

Food Web → Many interconnected food chains

1st Trophic Level → Producer

2nd → Primary Consumer

3rd → Secondary Consumer

Arrow → Direction of food/energy transfer

Energy → Decreases at successive trophic levels

Decomposers → Recycle nutrients

28. Concept Map | अवधारणा मानचित्र

29. Final Summary

A food chain is a linear sequence of organisms through which food and energy are transferred.

A food web is formed when several food chains become interconnected.

The first trophic level is occupied by producers. Primary, secondary and higher consumers occupy successive trophic levels.

Arrows show the direction of food and energy transfer.

Only a fraction of energy passes to each successive trophic level; the commonly taught value is about 10%.

Decomposers act on dead organic matter and recycle nutrients.

Quick Memory Trick:

🌱 Producer → Makes Food
🐇 Consumer → Takes Food
🍄 Decomposer → Breaks Down

Food Chain = One Pathway
Food Web = Many Connected Pathways

🌍 Class 10 Science | Our Environment

Food Chain • Food Web • Trophic Levels • Energy Flow • Ten Percent Law • Decomposers

CBSE + Foundation + Competitive Preparation

Class 10th Science Chapter 13 – Our Environment | Producers, Consumers and Decomposers

🌍 Our Environment

Producers, Consumers and Decomposers | Class 10 Science | CBSE + Foundation + Competitive

🌍 Our Environment | Producers, Consumers and Decomposers

1. Introduction | परिचय

An ecosystem contains different living organisms that perform different roles. On the basis of their method of obtaining food, organisms are broadly grouped as producers, consumers and decomposers.

हिंदी: पारितंत्र में विभिन्न जीव अलग-अलग भूमिकाएँ निभाते हैं। भोजन प्राप्त करने के तरीके के आधार पर जीवों को मुख्यतः उत्पादक, उपभोक्ता और अपघटक में बाँटा जाता है।

Producers → Consumers → Decomposers

Important: These three groups are interconnected and together help maintain the functioning of an ecosystem.

2. Producers | उत्पादक

Definition: Producers are organisms that prepare their own food, mainly through photosynthesis.

हिंदी: वे जीव जो अपना भोजन स्वयं बनाते हैं, मुख्यतः प्रकाश संश्लेषण द्वारा, उत्पादक (Producers) कहलाते हैं।

Examples:
🌱 Green plants
🌿 Grasses
🌊 Algae
🦠 Some photosynthetic microorganisms

Carbon dioxide + Water + Light Energy → Glucose + Oxygen

3. Why are Producers Important? | उत्पादक क्यों महत्वपूर्ण हैं?

• They capture solar energy.
• They convert light energy into chemical energy stored in food.
• They form the first trophic level.
• They provide food to herbivores.
• They indirectly support all higher trophic levels.
• Photosynthetic producers release oxygen.

Exam Point: The energy entering most ecosystems first becomes available to living organisms through producers.

4. Producers and Photosynthesis | उत्पादक एवं प्रकाश संश्लेषण

5. Consumers | उपभोक्ता

Consumers are organisms that obtain food directly or indirectly from other organisms.

हिंदी: वे जीव जो अपना भोजन सीधे या अप्रत्यक्ष रूप से अन्य जीवों से प्राप्त करते हैं, उपभोक्ता (Consumers) कहलाते हैं।

Consumers cannot generally manufacture their own food like green plants do.

Examples include: Deer, rabbit, frog, snake, tiger and humans.

6. Types of Consumers | उपभोक्ताओं के प्रकार

Type	Meaning	Examples
Primary Consumer	Feeds directly on producers	Deer, rabbit, grasshopper
Secondary Consumer	Feeds mainly on primary consumers	Frog, small fish
Tertiary Consumer	Feeds on lower-level consumers	Snake, large predatory fish
Omnivore	Consumes plant and animal food	Humans, bears

7. Primary Consumers | प्राथमिक उपभोक्ता

Primary consumers feed directly on producers. They are generally herbivores.

Examples: Deer, rabbit, cow, goat, grasshopper.

Grass → Deer
Producer → Primary Consumer

8. Secondary Consumers | द्वितीयक उपभोक्ता

Secondary consumers feed mainly on primary consumers.

Example:
Grass → Grasshopper → Frog

Grass = Producer
Grasshopper = Primary Consumer
Frog = Secondary Consumer

9. Tertiary and Higher Consumers | तृतीयक एवं उच्च उपभोक्ता

Tertiary consumers occupy higher trophic positions and generally feed on other consumers.

Example:
Grass → Grasshopper → Frog → Snake → Eagle

10. Omnivores | सर्वाहारी

Omnivores consume both plant and animal matter.

Examples: Humans and bears.

हिंदी: जो जीव पौधों और जन्तुओं दोनों से प्राप्त भोजन का सेवन करते हैं, उन्हें सर्वाहारी कहते हैं।

11. Decomposers | अपघटक

Decomposers are organisms that break down dead plants, animals and organic wastes into simpler substances.

हिंदी: जो जीव मृत पौधों, जन्तुओं तथा जैविक अपशिष्टों को सरल पदार्थों में तोड़ते हैं, उन्हें अपघटक (Decomposers) कहते हैं।

Main examples:
🍄 Fungi
🦠 Bacteria

12. Why are Decomposers Important? | अपघटक क्यों महत्वपूर्ण हैं?

• Break down dead organisms.
• Decompose organic wastes.
• Release nutrients into the environment.
• Help maintain soil fertility.
• Support nutrient cycling.
• Prevent excessive accumulation of dead matter.

13. Decomposition | अपघटन

Dead Organic Matter
↓
Decomposers
↓
Simpler Substances + Nutrients
↓
Environment

Decomposition is essential for returning nutrients from dead organisms to the environment.

14. Producers vs Consumers vs Decomposers

Feature	Producers	Consumers	Decomposers
Food source	Make their own food	Obtain food from other organisms	Obtain nutrients from dead organic matter
Examples	Plants, algae	Animals, humans	Bacteria, fungi
Role	Introduce energy into food chain	Transfer energy through feeding	Recycle nutrients
Trophic position	First trophic level	Higher trophic levels	Act across trophic levels

15. Producers, Consumers and Decomposers – Ecosystem Flow

16. Energy Flow and Nutrient Cycling

Energy flow:
Sun → Producers → Consumers

Energy flows through an ecosystem in a generally unidirectional manner and decreases at successive trophic levels.

Nutrient cycling:
Dead matter → Decomposers → Nutrients → Environment → Producers

17. Ten Percent Law | दस प्रतिशत नियम

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

1000 J → 100 J → 10 J → 1 J

The remaining energy is largely used in life processes and ultimately dissipated as heat.

18. Food Chain Examples | खाद्य श्रृंखला

Example 1:
Grass → Deer → Tiger

Example 2:
Grass → Grasshopper → Frog → Snake → Eagle

Example 3:
Phytoplankton → Small Fish → Large Fish

19. Food Web and the Three Groups

In a food web, several food chains are interconnected. Producers form the base of these feeding relationships, consumers occupy different trophic levels, and decomposers process dead organic matter from all levels.

20. Important Differences

Point	Producer	Consumer	Decomposer
Food preparation	Usually prepares food	Does not generally prepare food	Obtains nutrients from dead matter
Examples	Plants, algae	Animals	Bacteria, fungi
Main function	Energy capture	Energy transfer	Nutrient recycling
Importance	Starts most food chains	Connects trophic levels	Maintains nutrient availability

21. 30 MCQs | Multiple Choice Questions

1. Green plants are called:

A. Consumers

B. Producers

C. Decomposers

D. Parasites

Answer: B

2. Which organism is a decomposer?

A. Tiger

B. Deer

C. Mushroom

D. Grass

Answer: C

3. Primary consumers feed directly on:

A. Producers

B. Decomposers

C. Carnivores

D. Abiotic factors

Answer: A

4. Which is an example of a producer?

A. Frog

B. Grass

C. Snake

D. Tiger

Answer: B

5. Which organisms mainly break down dead organic matter?

A. Producers

B. Herbivores

C. Decomposers

D. Carnivores

Answer: C

6. Deer is generally a:

A. Primary consumer

B. Producer

C. Decomposer

D. Tertiary consumer

Answer: A

7. The first trophic level is occupied by:

A. Consumers

B. Producers

C. Decomposers

D. Carnivores

Answer: B

8. Which organism can be a secondary consumer?

A. Grass

B. Deer

C. Frog

D. Algae

Answer: C

9. Which organisms return nutrients to the environment?

A. Producers only

B. Decomposers

C. Herbivores only

D. Top carnivores only

Answer: B

10. The major energy source for most ecosystems is:

A. Soil

B. Water

C. Sunlight

D. Minerals

Answer: C

11. Which is generally an omnivore?

A. Human

B. Grass

C. Algae

D. Mushroom

Answer: A

12. Bacteria can act as:

A. Only producers

B. Decomposers

C. Only herbivores

D. Only carnivores

Answer: B

13. Fungi are important because many fungi act as:

A. Producers

B. Decomposers

C. Primary consumers

D. Top predators

Answer: B

14. Which sequence is correct?

A. Consumer → Producer → Sun

B. Sun → Producer → Consumer

C. Decomposer → Producer → Sun

D. Consumer → Sun → Producer

Answer: B

15. Producers obtain energy mainly from:

A. Sunlight

B. Tigers

C. Soil animals

D. Decomposers

Answer: A

16. Which is NOT a producer?

A. Grass

B. Algae

C. Deer

D. Green plant

Answer: C

17. Which is a secondary consumer in the chain Grass → Grasshopper → Frog?

A. Grass

B. Grasshopper

C. Frog

D. None

Answer: C

18. Approximately how much energy passes to the next trophic level?

A. 10%

B. 50%

C. 75%

D. 90%

Answer: A

19. Decomposers mainly help in:

A. Nutrient recycling

B. Producing sunlight

C. Increasing dead matter

D. Stopping decomposition

Answer: A

20. Which group forms the base of most food chains?

A. Producers

B. Carnivores

C. Decomposers

D. Parasites

Answer: A

21. A rabbit is generally a:

A. Primary consumer

B. Producer

C. Decomposer

D. Tertiary consumer

Answer: A

22. Which group obtains nutrients from dead organic matter?

A. Producers

B. Decomposers

C. Herbivores

D. Top predators

Answer: B

23. A tiger feeding on a deer is acting as a:

A. Producer

B. Primary consumer

C. Higher-level consumer

D. Decomposer

Answer: C

24. Which statement about producers is correct?

A. They depend directly on carnivores for food

B. They generally make their own food

C. They only decompose dead matter

D. They occupy the last trophic level

Answer: B

25. Which process is mainly associated with green producers?

A. Photosynthesis

B. Decomposition

C. Predation

D. Scavenging

Answer: A

26. Which pair is correctly matched?

A. Grass – Producer

B. Deer – Decomposer

C. Mushroom – Primary consumer

D. Tiger – Producer

Answer: A

27. What is the major role of consumers?

A. Capture sunlight directly

B. Transfer energy through feeding relationships

C. Produce soil minerals

D. Stop nutrient cycling

Answer: B

28. Which statement about decomposers is correct?

A. They recycle nutrients

B. They are always top predators

C. They produce sunlight

D. They never act on dead matter

Answer: A

29. Humans may be classified as:

A. Producers only

B. Decomposers only

C. Omnivorous consumers

D. Photosynthetic organisms

Answer: C

30. Which combination is correct?

A. Producers – food preparation

B. Consumers – direct nutrient recycling only

C. Decomposers – photosynthesis

D. Producers – decomposition

Answer: A

22. 30 Subjective Questions with Answers

2 Marks Q1. What are producers?

Producers are organisms that prepare their own food, mainly through photosynthesis. Green plants and algae are common examples.

2 Marks Q2. What are consumers?

Consumers are organisms that obtain food directly or indirectly from other organisms.

2 Marks Q3. What are decomposers?

Decomposers are organisms that break down dead organic matter into simpler substances. Bacteria and fungi are common examples.

2 Marks Q4. Give two examples of producers.

Green plants and algae.

2 Marks Q5. Give two examples of decomposers.

Bacteria and fungi.

3 Marks Q6. Why are green plants called producers?

They prepare their own food by photosynthesis using carbon dioxide, water and light energy. Therefore, they produce organic food for themselves and form the base of most food chains.

3 Marks Q7. What is the role of primary consumers?

Primary consumers feed directly on producers. They transfer energy stored in plant food to higher trophic levels.

3 Marks Q8. Why are decomposers important?

They decompose dead organisms, recycle nutrients and prevent accumulation of dead organic matter.

3 Marks Q9. Differentiate between producers and consumers.

Producers generally prepare their own food, while consumers obtain food from other organisms. Plants are common producers, whereas animals are consumers.

3 Marks Q10. What are omnivores? Give examples.

Omnivores are consumers that eat both plant and animal matter. Humans and bears are examples.

4 Marks Q11. Explain the importance of producers.

Producers capture solar energy, prepare food, form the first trophic level and provide energy-rich food to herbivores. They therefore support higher trophic levels.

4 Marks Q12. Explain the importance of consumers.

Consumers obtain food from other organisms and transfer energy from producers to higher trophic levels. They form important links in food chains and food webs.

4 Marks Q13. Explain the role of decomposers in nutrient cycling.

Decomposers break down dead plants, animals and organic wastes. This releases simpler substances and nutrients into the environment, making nutrients available for further use.

4 Marks Q14. Explain primary, secondary and tertiary consumers.

Primary consumers feed on producers. Secondary consumers feed mainly on primary consumers. Tertiary consumers occupy higher trophic positions and feed on lower-level consumers.

4 Marks Q15. Explain the relationship among producers, consumers and decomposers.

Producers make food, consumers obtain food from organisms and decomposers break down dead organic matter. The three groups are interconnected through energy transfer and nutrient cycling.

5 Marks Q16. Explain the process by which producers introduce energy into an ecosystem.

Green plants absorb light energy through photosynthetic pigments and use it to manufacture organic food. The energy becomes stored as chemical energy in food. Consumers obtain this energy by feeding on producers.

5 Marks Q17. Describe different types of consumers with examples.

Primary consumers feed on producers, e.g. deer. Secondary consumers feed mainly on primary consumers, e.g. frog in a grass–grasshopper–frog chain. Tertiary consumers occupy higher levels, e.g. snake or eagle in suitable food chains. Omnivores consume both plant and animal matter.

5 Marks Q18. Why are decomposers essential for maintaining an ecosystem?

They break down dead organic matter, prevent accumulation of dead material and recycle nutrients. Without effective decomposition, nutrient availability for producers would be reduced and ecosystem functioning would be disturbed.

5 Marks Q19. Explain the ten percent law in relation to producers and consumers.

Only about 10% of the energy available at one trophic level is transferred to the next trophic level. Thus, if producers contain 1000 J of available energy, approximately 100 J may reach the primary consumers and about 10 J the next level.

5 Marks Q20. Explain energy flow from producers to higher consumers.

Solar energy is captured by producers and stored as chemical energy. Primary consumers obtain this energy by eating producers. Secondary and higher consumers obtain energy by feeding on lower-level consumers. Energy decreases at successive trophic levels.

6 Marks Q21. Compare producers, consumers and decomposers in detail.

Producers	Consumers	Decomposers
Generally prepare their own food.	Obtain food from other organisms.	Obtain nutrients from dead organic matter.
Plants and algae.	Animals and humans.	Bacteria and fungi.
Capture energy.	Transfer energy.	Recycle nutrients.

6 Marks Q22. Explain how decomposers connect the living and non-living components of an ecosystem.

Decomposers act on dead organisms and organic wastes. They convert complex organic matter into simpler substances and release nutrients back into the environment. These nutrients can then be absorbed by plants. Thus decomposers link dead biological material with the abiotic environment and help maintain nutrient cycling.

6 Marks Q23. Explain the complete pathway of energy and nutrients involving producers, consumers and decomposers.

Sunlight provides the initial energy. Producers convert it into chemical energy in food. Consumers obtain this energy by feeding on producers or other consumers. When organisms die, decomposers break down their remains and release nutrients. These nutrients become available to producers again, while energy is not recycled in the same way and progressively dissipates as heat.

6 Marks Q24. What would happen if producers disappeared from an ecosystem?

The major entry of energy into the food chain would stop. Primary consumers would lose their main food source, followed by secondary and higher consumers. Food chains would collapse and the ecosystem would be severely disturbed.

6 Marks Q25. What would happen if decomposers disappeared?

Dead organic matter would accumulate, decomposition would slow dramatically and nutrient recycling would be disrupted. Over time, producers would face reduced nutrient availability, affecting consumers and the whole ecosystem.

6 Marks Q26. Explain why producers are the foundation of most ecosystems.

Producers capture solar energy and convert it into chemical energy stored in food. This energy supports herbivores and, indirectly, all higher consumers. Therefore producers form the energetic foundation of most ecosystems.

6 Marks Q27. Explain the role of decomposers in soil fertility.

Decomposers break down dead plant and animal matter and release simpler nutrients into the environment. These nutrients can become available to plants, helping maintain nutrient availability and soil fertility.

6 Marks Q28. Explain why consumers cannot be removed from a food chain without consequences.

Consumers transfer energy between trophic levels and regulate populations through feeding relationships. Removing a consumer can alter the abundance of its food organisms and predators, disturbing the balance of the food web.

6 Marks Q29. Explain the statement: "Decomposers are nature's recyclers."

Decomposers process dead organic matter and return nutrients to the environment. These nutrients can be reused by producers. In this way, decomposers help recycle essential elements within ecosystems.

6 Marks Q30. Write a detailed note on producers, consumers and decomposers.

Producers, consumers and decomposers are the major functional groups of organisms in an ecosystem. Producers such as green plants manufacture food and capture solar energy. Consumers obtain food directly or indirectly from other organisms and transfer energy through trophic levels. Decomposers such as bacteria and fungi break down dead organic matter and recycle nutrients. These three groups are interconnected and essential for ecosystem functioning.

23. Assertion–Reason Questions

Assertion (A): Green plants are producers.
Reason (R): Green plants generally prepare their own food by photosynthesis.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Decomposers are important for nutrient recycling.
Reason (R): Decomposers break down dead organic matter.

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Primary consumers generally occupy the first trophic level.
Reason (R): Primary consumers feed directly on producers.

Answer: Assertion is false, but Reason is true.
The first trophic level is occupied by producers.

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

Answer: Both A and R are true, and R correctly explains A.

Assertion (A): Consumers depend directly or indirectly on producers.
Reason (R): Producers form the base of most food chains.

Answer: Both A and R are true, and R correctly explains A.

24. HOTS | Higher Order Thinking Questions

HOTS 1: Why would a forest ecosystem be seriously affected if green plants were removed?

Green plants are the main producers. Their removal would stop the main entry of solar energy into the food chain and reduce food availability for herbivores and higher consumers.

HOTS 2: Why is decomposition essential even though decomposers do not produce food?

Decomposers recycle nutrients from dead organic matter. These nutrients become available again to producers, making decomposition essential for continued ecosystem functioning.

HOTS 3: Why is the energy pathway different from nutrient cycling?

Energy enters mainly from the Sun and flows through trophic levels, with much being dissipated as heat. Nutrients, however, are repeatedly recycled between organisms and the physical environment.

HOTS 4: A field has many plants but very few decomposers. What long-term problem could develop?

Dead organic matter could accumulate and nutrient recycling would decrease. Over time, nutrient availability to plants could decline.

HOTS 5: Why can an ecosystem not depend only on producers?

Producers provide food and energy, but consumers transfer this energy through feeding relationships and decomposers recycle nutrients. All groups perform complementary roles.

25. Important Exam Diagrams

Remember these three diagrams:

1. Energy Flow:
☀ Sun → 🌱 Producers → 🐇 Consumers

2. Decomposition:
Dead Matter → 🍄 Decomposers → Nutrients

3. Complete Ecosystem Relationship:
Sun → Producers → Consumers → Dead Matter → Decomposers → Nutrients → Producers

26. Golden Points | परीक्षा के लिए महत्वपूर्ण

✔ Green plants are major producers.

✔ Producers form the first trophic level.

✔ Primary consumers generally feed on producers.

✔ Secondary consumers generally feed on primary consumers.

✔ Tertiary consumers occupy higher trophic levels.

✔ Humans are generally omnivorous consumers.

✔ Bacteria and fungi are important decomposers.

✔ Decomposers recycle nutrients.

✔ Energy flow is generally unidirectional.

✔ Approximately 10% of energy is transferred to the next trophic level.

✔ Energy is not recycled through the ecosystem in the same way nutrients are.

27. One-Minute Revision

Producer → Makes food

Primary Consumer → Eats producer

Secondary Consumer → Eats primary consumer

Tertiary Consumer → Higher-level consumer

Decomposer → Breaks dead matter

Energy Flow → Sun → Producer → Consumer

Nutrient Cycling → Dead matter → Decomposer → Nutrients

Ten Percent Law → About 10% energy moves to the next trophic level

28. Concept Map | अवधारणा मानचित्र

29. Final Summary

Producers are organisms that generally prepare their own food and form the first trophic level.

Consumers depend directly or indirectly on other organisms for food. They include primary, secondary, tertiary and omnivorous consumers.

Decomposers such as bacteria and fungi break down dead organic matter and recycle nutrients.

The three groups are closely connected:

☀ Sun → 🌱 Producers → 🐇 Consumers → ☠ Dead Matter → 🍄 Decomposers → Nutrients → 🌱 Producers

The key distinction to remember is:

Producers = Make food
Consumers = Obtain food
Decomposers = Break down dead matter & recycle nutrients

🌍 Class 10 Science | Our Environment

Producers • Consumers • Decomposers • Food Chain • Trophic Levels • Energy Flow • Nutrient Cycling

CBSE + Foundation + Competitive Preparation