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📝 Energy flow in ecosystems food chain (7 MCQs)

📖 From Campbell Biology • 1. Evolution and the theme of Biology and Scientific Inquiry • 7 questions available

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What is Energy flow in ecosystems food chain?

Definition:
Energy flow in an ecosystem describes the movement of energy from the Sun to producers and then through consumers in a food chain. Energy is transferred between organisms when one organism eats another, while much energy is ultimately released as heat.

Working:
Producers capture energy, usually from sunlight, and store it as chemical energy. Consumers obtain energy by feeding on producers or other consumers.

Example:
In the chain grass $\rightarrow$ grasshopper $\rightarrow$ frog $\rightarrow$ snake, energy moves from grass to grasshopper, then frog, and finally snake.

Reason:
Energy decreases at higher trophic levels because organisms use much of the acquired energy for metabolism, movement, growth, and maintenance, with significant amounts dissipated as heat.

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📝 All Energy flow in ecosystems food chain MCQs

Q1. A grassland receives sunlight, but producers capture only a small fraction of that energy. Which sequence best represents what happens to most captured energy as it moves through the ecosystem?

A.It is repeatedly recycled as usable energy among trophic levels

B.It is transferred upward and eventually released as heat through metabolic processes ✅

C.It is stored permanently in consumers and never lost

D.It is converted back into sunlight by decomposers

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Energy enters ecosystems primarily as sunlight and is captured by producers. As energy passes to consumers, much is used in metabolism and ultimately released as heat. Unlike matter, usable energy is not repeatedly recycled through trophic levels.

Q2. Two ecosystems receive equal amounts of sunlight. Ecosystem X has highly productive plants, while ecosystem Y has plants with low photosynthetic efficiency. If all other conditions are similar, which prediction is most reasonable?

A.Ecosystem Y must contain more energy at every consumer level

B.Ecosystem X can support greater energy transfer to consumers because more solar energy becomes chemical energy ✅

C.Both ecosystems must support identical consumer biomass because sunlight input is equal

D.Ecosystem X will lose all captured energy immediately as heat

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Equal sunlight input does not guarantee equal energy available to consumers. Producers differ in how efficiently they convert light into chemical energy, so higher producer productivity can provide a larger energy base for herbivores and higher trophic levels.

Q3. A researcher estimates that plants store 20,00020{,}000 kJ of chemical energy. Herbivores obtain approximately 10%10\% of the producer energy, and carnivores obtain approximately 10%10\% of herbivore energy. Ignoring other losses, about how much energy reaches carnivores?

A.2 kJ

B.20 kJ ✅

C.200 kJ

D.2,000 kJ

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: The herbivores receive about 10%10\% of 20,00020{,}000 kJ, giving 2,0002{,}000 kJ. Carnivores then receive approximately 10%10\% of that amount, or 200200 kJ. However, because the question asks about the stated sequential transfers, the correct value is 200200 kJ.

Q4. A student claims, Because consumers eat producers, nearly all chemical energy in plants becomes consumer biomass." Which part of the reasoning is incorrect?"

A.Consumers cannot obtain any chemical energy from producers

B.Much of the consumed energy is used for metabolism, movement, maintenance, and other processes rather than becoming new biomass ✅

C.Plants contain only heat energy rather than chemical energy

D.Consumer biomass is converted directly into sunlight

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The misconception is assuming that consumption equals biomass production. Consumers use absorbed energy for cellular respiration, movement, maintenance, growth, and reproduction. A substantial portion is ultimately dissipated as heat, so only part contributes to new consumer biomass.

Q5. A graph shows available energy decreasing from 12,00012{,}000 kJ in producers to 1,2001{,}200 kJ in primary consumers and 120120 kJ in secondary consumers. If the pattern continues, which prediction is most consistent with the graph?

A.Tertiary consumers would receive approximately 1212 kJ ✅

B.Tertiary consumers would receive approximately 1,2001{,}200 kJ

C.Tertiary consumers would receive approximately 120,000120{,}000 kJ

D.Tertiary consumers would receive exactly 10,00010{,}000 kJ

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: The graph indicates an approximately tenfold decrease in available energy at each successive trophic transfer. Applying the observed pattern, 120120 kJ would decrease to about 1212 kJ for tertiary consumers.

Q6. An ecosystem loses most of its producer biomass because of drought. At the same time, decomposers continue functioning normally. Which outcome best explains the likely effect on higher consumers?

A.Higher consumers will increase because decomposers create additional solar energy

B.Energy available to higher consumers will decline because less producer-derived chemical energy enters the food web ✅

C.Higher consumers will remain completely unaffected because heat replaces lost producer energy

D.Higher consumers will gain energy directly from atmospheric oxygen

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Producers form the primary energy entry point for most ecosystems. A reduction in producer biomass lowers the amount of chemical energy available to herbivores, which then reduces energy available to higher consumers despite continued decomposer activity.

Q7. A simplified ecosystem model receives 100,000100{,}000 energy units from sunlight. Producers capture 2%2\%, primary consumers obtain 10%10\% of producer energy, and secondary consumers obtain 10%10\% of primary-consumer energy. Which conclusion is best supported?

A.Secondary consumers receive 2,0002{,}000 units

B.Secondary consumers receive 2020 units ✅

C.Only 2%2\% of sunlight reaches producers, so secondary consumers receive 200200 units

D.Secondary consumers receive 10,00010{,}000 units because consumer transfer is more efficient than producer capture

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: First, producers capture 2%2\% of 100,000100{,}000, giving 2,0002{,}000 units. Primary consumers receive 10%10\%, or 200200 units. Secondary consumers then receive 10%10\% of 200200, producing 2020 units. The multi-step model shows why little energy remains at higher trophic levels.

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