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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।
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।
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
सूर्य
→
🌱 Producers
उत्पादक
उत्पादक
→
🐇 Primary Consumers
प्राथमिक उपभोक्ता
प्राथमिक उपभोक्ता
→
🦊 Secondary Consumers
द्वितीयक उपभोक्ता
द्वितीयक उपभोक्ता
→
🦅 Tertiary Consumers
तृतीयक उपभोक्ता
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
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।
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।
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
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
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।
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
घास
→
🐗 Grasshopper
टिड्डा
टिड्डा
→
🐸 Frog
मेंढक
मेंढक
→
🐍 Snake
साँप
साँप
→
🦅 Eagle
गरुड़
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।
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।
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
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?
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।
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?
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?
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?
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?
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.
Q6. Calculate 10% of 5,000 J.
10% × 5,000 = 500 J
3 Marks
Q7. Explain energy transfer from producers to secondary consumers.
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.
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?
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?
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.
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.
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.
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.
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?
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.”
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.
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
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.
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.
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.
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.
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.
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.
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
Energy Flow and 10% Law | ऊर्जा प्रवाह एवं 10% नियम
