CUET UG Biology Booster Test 3-Energy Flow and Trophic Levels -

🚀

CUET UG Biology Booster Test 3-Energy Flow and Trophic Levels

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Biology Booster Test 3-Energy Flow and Trophic Levels

1 / 20

QUESTION 1 OF 20

If a localized atmospheric phenomenon were to block entirely the wavelengths comprising Photosynthetically Active Radiation (PAR) while allowing the rest of incident solar radiation to pass, what would be the analytical outcome for that ecosystem?

Answer Review

1 If a localized atmospheric phenomenon were to block entirely the wavelengths comprising Photosynthetically Active Radiation (PAR) while allowing the rest of incident solar radiation to pass, what would be the analytical outcome for that ecosystem?

A GPP would increase due to adaptation to other wavelengths.

B Primary productivity would halt, leading to the collapse of the energy flow sustaining the ecosystem.

C The detritus food chain would immediately become independent of solar energy.

D Omnivores would shift strictly to chemolithotrophy.

💡 Short Explanation

PAR is the essential spectral range for photosynthesis. Without PAR, autotrophs cannot fix energy. Energy flow in an ecosystem is entirely dependent on this primary input.

✅ Correct Answer Explanation

Photosynthesis is exclusively driven by PAR. If these wavelengths are removed, producers cannot convert solar energy into chemical energy (GPP). → Since the entire ecosystem (GFC and DFC) relies on the energy captured by producers, the removal of PAR results in a total collapse of energy flow. Option B correctly identifies this critical dependency.

❓ Why Other Options Are Incorrect

Option A → Adaptation is a long-term evolutionary process, not an analytical outcome of a sudden atmospheric block.
Option C → The DFC is fundamentally powered by dead organic matter originally created by solar energy; it cannot become "independent."
Option D → Omnivores are heterotrophs; they cannot evolve into chemolithotrophs (autotrophs) instantaneously.

🎯 Strategy

Used: Elimination

Application: Eliminating scenarios that violate biological principles (e.g., instant metabolic change or GPP increase without light).

Final Logic: No PAR = No Photosynthesis = No Ecosystem.

🧠 Memory Trick

"No Light = No Life."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow/PAR

2 Analyze the statements regarding solar incident energy:
I. Since less than 50% of incident radiation is PAR, plant gross primary productivity is fundamentally limited by available spectral quality.
II. Deep-sea hydro-thermal ecosystems completely bypass the need for incident solar radiation for their energy input.
III. Ecosystems require sporadic inputs of solar energy rather than a constant supply to function. Which are analytically true?

A II and III

B I and II

C I and III

D I, II, and III

💡 Short Explanation

I is true: Spectral limitation is a constraint on GPP. II is true: Deep-sea vents use chemosynthesis. III is false: Ecosystems require a constant supply, not sporadic.

✅ Correct Answer Explanation

Statement I is correct because light quality is a primary limiting factor for photosynthesis. → Statement II is correct because hydrothermal vents are the only known ecosystems independent of incident solar radiation. → Statement III is false because thermodynamics dictates that ecosystems must have a constant, non-sporadic energy source to overcome entropy.

❓ Why Other Options Are Incorrect

Option A → Statement III is incorrect (requires constant supply).
Option C → Statement II is true (hydrothermal vents bypass solar).
Option D → Statement III is incorrect.

🎯 Strategy

Used: Substitution

Application: Evaluating each statement against the Second Law of Thermodynamics and ecological definitions.

Final Logic: I & II are facts; III is scientifically incorrect.

🧠 Memory Trick

"Solar = Constant; Vents = Chemical."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

3 Despite capturing only 2 to 10 percent of PAR, plants sustain the entire living world. Analytically, what does this demonstrate regarding the Gross Primary Productivity (GPP) versus absolute incident energy?

A The absolute magnitude of incident PAR is immense enough that a mere 2-10% capture is biologically profound.

B GPP relies on 100% efficiency of photosynthesis.

C Net Primary Productivity (NPP) is greater than GPP.

D Respiration losses (R) account for 90-98% of PAR.

💡 Short Explanation

Efficiency is low (2-10%), but the total input is massive. Total input energy supports all global biomass. GPP is a product of this input.

✅ Correct Answer Explanation

Total solar radiation reaching Earth is vast. Even a small fraction (2-10%) converted to chemical energy (GPP) is sufficient to fuel all life processes across the biosphere. → Option A reflects the correct analytical scale of energy input versus ecological output.

❓ Why Other Options Are Incorrect

Option B → 100% efficiency is physically impossible (violates thermodynamics).
Option C → GPP is always greater than or equal to NPP (GPP = NPP + R).
Option D → Respiration consumes a portion of GPP, not a portion of the incoming PAR light itself.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Matching the scale of solar energy input to the sustained global biomass.

Final Logic: Massive Input × Small % = Sufficient Energy for Life.

🧠 Memory Trick

"Big Sun, Small Slice = Enough Life."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Productivity

4 Which pathway analytically contradicts the rule of how captured solar energy sustains the living world?

A Radiant Energy -> Autotroph -> Herbivore -> Secondary Consumer

B Radiant Energy -> Producer -> Detritus -> Saprotroph

C Radiant Energy -> Primary Carnivore -> Herbivore -> Autotroph

D Autotroph -> Dead Biomass -> Detritus Food Chain

💡 Short Explanation

Energy flows from Autotroph (Producer) upwards. Energy cannot flow from Carnivore to Herbivore to Autotroph. Option C depicts a reverse flow (anti-thermodynamic).

✅ Correct Answer Explanation

Energy flow is unidirectional (Producer → Consumer). → Option C depicts energy moving from a carnivore backwards to a producer, which is an analytical impossibility in ecology.

❓ Why Other Options Are Incorrect

Option A → Standard GFC pathway.
Option B → Pathway to DFC.
Option D → Transfer of biomass to DFC.

🎯 Strategy

Used: Elimination

Application: Finding the sequence that violates the directional flow of energy (Sun to Producer to Consumer).

Final Logic: Direction is Producer to Consumer, never Consumer to Producer.

🧠 Memory Trick

"Flow: Bottom-up, never top-down."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

5 Match the thermodynamic implication to its ecological reality:

Column 1	Column 2
1. Need for constant energy supply	A. Proves the 10 per cent law restriction.
2. Dissipation of heat	B. Energy cannot be passed from producers back to the sun.
3. Unidirectional flow	C. Counteracts universal disorderliness (2nd Law).
4. Decreasing energy at successive levels	D. Represents loss to the environment during transfer.

A 1-B, 2-D, 3-A, 4-C

B 1-A, 2-B, 3-C, 4-D

C 1-C, 2-A, 3-B, 4-D

D 1-C, 2-D, 3-B, 4-A

💡 Short Explanation

Constant energy counteracts disorder (1-C). Heat dissipation is loss (2-D). Unidirectional means no back-flow (3-B). Decreasing energy = 10% law (4-A).

✅ Correct Answer Explanation

1-C: Constant energy is required to maintain order (Second Law). → 2-D: Heat is lost during each energy transfer. → 3-B: Flow is one-way (Sun to Consumer, not back). → 4-A: Energy reduction at levels is defined by the 10% law.

❓ Why Other Options Are Incorrect

All other options scramble the correct ecological-thermodynamic definitions.

🎯 Strategy

Used: Option Grouping

Application: Mapping each thermodynamic law to its corresponding NCERT ecological definition.

Final Logic: Direct logical pairing.

🧠 Memory Trick

"1-C, 2-D, 3-B, 4-A."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

6 Which of the following analytical statements is NOT associated with the thermodynamic constraints of an ecosystem?

A Energy trapped by a producer is eventually dissipated as heat or passed on; it never remains forever.

B The First Law is upheld as radiant energy is transformed into chemical food energy without being created or destroyed.

C Ecosystems are closed systems that do not require external energy to maintain ordered standing crops.

D Increasing disorderliness is continuously counteracted by synthesizing required molecules using energy.

💡 Short Explanation

Ecosystems are open systems. They require external energy (sun). Statement C is fundamentally false.

✅ Correct Answer Explanation

Ecosystems are open systems requiring constant solar energy. Calling them "closed systems that do not require external energy" is an analytical error. → All other statements are correct thermodynamic principles applied to ecosystems.

❓ Why Other Options Are Incorrect

Option A, B, D → These are all correct thermodynamic statements per NCERT.

🎯 Strategy

Used: Elimination

Application: Identifying the statement that contradicts the definition of an ecosystem as an open system.

Final Logic: Ecosystems = Open, need energy.

🧠 Memory Trick

"Ecosystem = Open System."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Thermodynamics

7 Evaluate the functional role of producers in varied ecosystems:
I. Terrestrial herbaceous and woody plants contribute to vertical stratification while fixing PAR.
II. Aquatic phytoplankton possess high turnover rates, heavily driving the aquatic GFC.
III. Terrestrial producers provide a significantly larger input into the DFC compared to aquatic producers. Which of these deep concepts are accurate?

A I and II

B II and III

C I and III

D I, II, and III

💡 Short Explanation

I is true: Vertical strata in forests are classic. II is true: Phytoplankton have rapid growth/turnover. III is true: Terrestrial systems are DFC-dominated.

✅ Correct Answer Explanation

All three statements are accurate. Terrestrial plants create vertical structure (stratification). Phytoplankton in water have rapid generation times (turnover) fueling GFC. Terrestrial ecosystems have a large biomass (woody plants) that enters the DFC.

❓ Why Other Options Are Incorrect

A, B, C → All are incomplete as all three statements hold truth.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Checking the validity of each deep ecological concept presented.

Final Logic: All statements align with NCERT knowledge.

🧠 Memory Trick

"Producers do all three: Stratify, Turn over, Feed DFC."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Producers

8 Which of the following is NOT an analytically valid characteristic of aquatic producers compared to terrestrial producers?

A Aquatic producers like phytoplankton generally lack complex lignified (woody) structures.

B They primarily drive the Grazing Food Chain (GFC) as the major conduit of energy flow in their ecosystem.

C They capture PAR efficiently enough to sustain complex aquatic food webs.

D They act as the major conduit for energy flow through the Detritus Food Chain in aquatic systems.

💡 Short Explanation

Aquatic systems are GFC-dominated. Terrestrial systems are DFC-dominated. Statement D is false.

✅ Correct Answer Explanation

In aquatic ecosystems, the GFC is the major conduit, not the DFC. Therefore, D is analytically invalid. → A, B, and C are correct facts about aquatic producers (phytoplankton).

❓ Why Other Options Are Incorrect

Option A, B, C → All these are correct descriptions of aquatic producers.

🎯 Strategy

Used: Elimination

Application: Differentiating between aquatic (GFC-dominant) and terrestrial (DFC-dominant) energy flow.

Final Logic: Aquatic = GFC, so D is wrong.

🧠 Memory Trick

"Aquatic = GFC; Terrestrial = DFC."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

9 Arrange the following biological events conceptually to trace energy from the sun to a secondary heterotroph:
1. Primary carnivore breaks down prey tissue for its own metabolism.
2. Incident solar radiation (PAR) is fixed via photosynthesis.
3. Herbivorous insect ingests plant matter.
4. Herbivore's biomass acts as nutrition for a secondary consumer.

A 2, 3, 4, 1

B 3, 2, 1, 4

C 2, 4, 3, 1

D 1, 3, 2, 4

💡 Short Explanation

2 (Fixation) → 3 (Herbivore eats) → 4 (Secondary consumer gets biomass) → 1 (Carnivore metabolism).

✅ Correct Answer Explanation

The flow: Solar radiation fixed by producers (2) → Herbivore eats producer (3) → Herbivore is consumed by secondary carnivore (4) → Carnivore uses tissue for metabolism (1).

❓ Why Other Options Are Incorrect

B, C, D → Incorrect chronological order of biological energy transfer.

🎯 Strategy

Used: Substitution

Application: Ordering the flow from producer to primary consumer to secondary consumer.

Final Logic: Solar → Producer → Herbivore → Carnivore.

🧠 Memory Trick

"Fix → Eat → Get Energy → Burn."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Trophic Levels

10 In a deeply structured food web, a sparrow eating a seed is a primary consumer, but eating a worm makes it a secondary consumer. Analytically, what does this prove about secondary/tertiary heterotroph classifications?

A They are rigid anatomical classifications fixed at birth.

B Trophic levels represent a functional level based on the immediate source of nutrition, not a species as such.

C Sparrows violate the unidirectional flow of energy.

D The pyramid of numbers must be inverted.

💡 Short Explanation

Trophic level is functional, not species-based. One species can occupy multiple levels. This proves functionality.

✅ Correct Answer Explanation

The sparrow's trophic position depends on what it eats, not what it is. This proves that trophic levels are functional stages, not fixed species definitions.

❓ Why Other Options Are Incorrect

Option A → Incorrect; if they were rigid, the sparrow couldn't switch roles.
Option C → Incorrect; the energy still flows one way through the levels.
Option D → Incorrect; this has no bearing on pyramids.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Matching the scenario (changing diet, changing level) to the definition of "functional trophic level."

Final Logic: Diet change = Level change = Functional.

🧠 Memory Trick

"Level = Functional."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Trophic Levels

11 Match the energy flow dynamics within the GFC:

Column 1	Column 2
1. Producer to Primary Consumer	A. Major conduit for energy flow in water bodies.
2. Primary Carnivore to Secondary Carnivore	B. Herbivory transfer.
3. GFC to Detritus	C. Tertiary consumer nutrition source.
4. Aquatic GFC specific trait	D. Energy flow upon death of organism

A 1-B, 2-D, 3-A, 4-C

B 1-A, 2-B, 3-C, 4-D

C 1-B, 2-C, 3-D, 4-A

D 1-C, 2-A, 3-D, 4-B

💡 Short Explanation

1-B: Herbivory transfer. 2-C: Tertiary consumer nutrition source (the primary carnivore is the prey). 3-D: Death leads to detritus. 4-A: Aquatic systems are GFC-driven.

✅ Correct Answer Explanation

1 (Producer to C1) is the definition of herbivory (B). → 2 (Primary to Secondary carnivore) involves the secondary carnivore eating the primary, placing the primary as the nutrition source (C). → 3 (GFC to Detritus) occurs upon the death of an organism (D). → 4 (Aquatic trait) is that GFC is the major conduit (A).

❓ Why Other Options Are Incorrect

All other options incorrectly map the definitions to the specific dynamics of the GFC.

🎯 Strategy

Used: Option Grouping

Application: Logical association of biological terms to their definitions in the Grazing Food Chain.

Final Logic: Proper alignment of definitions.

🧠 Memory Trick

"1-Herb, 2-Prey, 3-Death, 4-Aquatic Major."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

12 Which statement analytically is NOT associated with the functioning of the Grazing Food Chain (GFC)?

A The number of trophic levels is functionally restricted by the rapid loss of energy (10% law).

B Energy trapped into an organism in the GFC remains in it forever if it evades predation.

C The GFC provides the primary structural basis for the upright pyramid of energy.

D It often interconnects with the DFC at various levels.

💡 Short Explanation

Energy is never permanent (thermodynamics). Metabolism dissipates energy constantly. Statement B is false.

✅ Correct Answer Explanation

Energy in an organism is continuously used for metabolic processes (respiration) and dissipated as heat, whether it is preyed upon or not. Nothing "remains forever" in a biological system.

❓ Why Other Options Are Incorrect

Option A, C, D → All these are correct analytical truths about the GFC.

🎯 Strategy

Used: Elimination

Application: Recognizing the false statement regarding the transient nature of energy in biological systems.

Final Logic: Energy is transient, never permanent.

🧠 Memory Trick

"Energy = Transient."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Flow

📄 Passage

"In an aquatic ecosystem, GFC is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC. Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web."

Based on the passage, why analytically does a much larger fraction of energy flow through the DFC in a terrestrial ecosystem compared to an aquatic one?

A Terrestrial autotrophs (like woody plants) produce massive amounts of complex biomass that heavily enters the dead organic matter pool.

B Terrestrial ecosystems possess zero primary producers.

C Aquatic ecosystems entirely lack saprotrophic fungi and bacteria.

D Terrestrial herbivores are universally inefficient at eating plants.

💡 Short Explanation

Terrestrial producers have high biomass/woody tissue. Large portions are not consumed by herbivores and thus fall as litter. This litter drives the DFC.

✅ Correct Answer Explanation

Woody plants produce large amounts of structural carbon (lignin/cellulose) that herbivores cannot easily digest or consume. This biomass accumulates as dead organic matter, fueling the DFC.

❓ Why Other Options Are Incorrect

Option B → Incorrect; terrestrial systems have abundant producers.
Option C → Incorrect; aquatic systems have plenty of decomposers.
Option D → Incorrect; inefficiency is not the primary cause of DFC dominance.

🎯 Strategy

Used: Substitution

Application: Comparing terrestrial biomass structure to energy flow dominance.

Final Logic: High Structural Biomass = DFC Dominance.

🧠 Memory Trick

"Wood = Detritus Pool."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Detritus Food Chain

📄 Passage

According to the passage, what specific mechanism allows saprotroph-driven degradation networks (DFC) to re-enter the higher trophic levels of the Grazing Food Chain (GFC)?

A Saprotrophs evolve into primary producers.

B Dead organic matter spontaneously transforms into living herbivores.

C Organisms of the DFC become prey to GFC animals, forming interconnected web links.

D Decomposers secrete enzymes that photosynthesize.

💡 Short Explanation

DFC organisms (like worms) are eaten by GFC animals (like birds). This connects the two chains.

✅ Correct Answer Explanation

The passage states that DFC organisms are prey to GFC animals. This creates a link, allowing energy to move between these two distinct pathways.

❓ Why Other Options Are Incorrect

Option A, B, D → These are biologically impossible mechanisms.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Extracting the mechanism mentioned in the passage provided.

Final Logic: DFC → Prey for GFC = Link.

🧠 Memory Trick

"DFC organism = GFC food."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Food Web

15 Arrange the conceptual steps that illustrate the complex interconnection of chains via an omnivore:
1. Plant dies, contributing to detritus.
2. Earthworm (DFC) processes the dead plant.
3. Incident PAR is fixed by a terrestrial plant.
4. A crow (omnivore) consumes the earthworm.

A 1, 2, 3, 4

B 1, 3, 4, 2

C 3, 2, 1, 4

D 3, 1, 2, 4

💡 Short Explanation

Fixation (3) → Death (1) → Decomposer (2) → Omnivore eats decomposer (4).

✅ Correct Answer Explanation

Energy flows from solar fix (3) to plant biomass, then the plant dies (1) and becomes detritus, which is processed by the worm (2), and finally consumed by the crow (4).

❓ Why Other Options Are Incorrect

A, B, C → Incorrect sequence of energy accumulation and transfer.

🎯 Strategy

Used: Substitution

Application: Tracing the path of energy from producer to detritus to consumer.

Final Logic: Solar → Dead → Detritivore → Omnivore.

🧠 Memory Trick

"Fix → Die → Worm → Crow."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Food Web

16 Analytically, which of the following is NOT a consequence of omnivore presence and natural prey interconnections in an ecosystem?

A It transforms isolated linear food chains into complex food webs.

B It allows a single species to function at multiple trophic levels simultaneously.

C It stabilizes the ecosystem by providing alternative feeding pathways.

D It invalidates the first law of thermodynamics by creating cyclic energy generation.

💡 Short Explanation

Thermodynamic laws are never invalidated. Energy is not cyclic. Statement D is false.

✅ Correct Answer Explanation

Energy flow is never cyclic (it's unidirectional). Thermodynamics cannot be invalidated.

❓ Why Other Options Are Incorrect

Option A, B, C → All these are correct ecological consequences of food webs.

🎯 Strategy

Used: Elimination

Application: Eliminating statements that violate fundamental physical laws.

Final Logic: Laws of Physics are absolute.

🧠 Memory Trick

"No Cycle = No Loop."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Thermodynamics

17 In deep analytical terms, a trophic level is best defined as:

A A strict taxonomic grouping of organisms.

B A functional level representing a specific stage of energy transfer and source of nutrition, regardless of the individual species occupying it.

C A strictly spatial layer within the ecosystem's stratification.

D The total biomass of decomposers in the soil.

💡 Short Explanation

Trophic level = Functional energy stage. Species are irrelevant to the level's definition.

✅ Correct Answer Explanation

Trophic level is a classification based on energy transfer distance from the producer. Any species can potentially fit into different levels based on its diet.

❓ Why Other Options Are Incorrect

Option A, C, D → Incorrect definitions based on taxonomy, space, or biomass.

🎯 Strategy

Used: Substitution

Application: Selecting the definition that emphasizes the "functional" nature of trophic ecology.

Final Logic: Level = Functional Energy Stage.

🧠 Memory Trick

"Trophic = Functional Level."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Trophic Levels

18 Analytically, why is it functionally impossible for a heterotroph to reside at the first trophic level?

A Heterotrophs are incapable of utilizing the sun's radiant energy to synthesize simple inorganic materials into organic food.

B Heterotrophs possess too large a standing crop.

C Heterotrophs only consume 10% of available energy.

D Heterotrophs reside permanently in the Detritus Food Chain.

💡 Short Explanation

First level = Producers (Autotrophs). Heterotrophs = Consumers. Consumers cannot fix light energy.

✅ Correct Answer Explanation

The first trophic level is reserved for autotrophs that fix solar energy (Photosynthesizers). Heterotrophs require pre-formed organic matter and lack the biological machinery to perform photosynthesis.

❓ Why Other Options Are Incorrect

Option B, C, D → These are incorrect or irrelevant justifications.

🎯 Strategy

Used: Elimination

Application: Determining the defining trait of the first trophic level (autotrophy).

Final Logic: Heterotroph ≠Autotroph (Producer).

🧠 Memory Trick

"First = Producer = Light User."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Trophic Levels

19 Consider the analytical implications of the Ten Per Cent Transfer Law:
I. It logically explains why the pyramid of energy is strictly upright and can never be inverted.
II. It is the primary limiting factor preventing grazing food chains from having an infinite number of trophic tiers.
III. It dictates that 90% of energy is perfectly assimilated into standing crop at each level. Which are analytically correct?

A I and III

B II and III

C I and II

D All of the above

💡 Short Explanation

I is true: Energy loss prevents inversion. II is true: Energy limits chain length. III is false: Energy is lost (dissipated as heat), not assimilated.

✅ Correct Answer Explanation

Statements I and II are correct. Statement III is false because 90% of energy is lost as heat/metabolism, not assimilated into biomass (standing crop).

❓ Why Other Options Are Incorrect

Option A, B, D → All contain the false Statement III.

🎯 Strategy

Used: Elimination

Application: Testing the 10% law's impact on energy pyramids vs. assimilation rates.

Final Logic: Energy is lost, not assimilated.

🧠 Memory Trick

"10% Up, 90% Heat."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Transfer

20 If a prolonged environmental stress rapidly decreases the GPP of the first trophic level, what is the mathematically inevitable thermodynamic consequence on the fourth trophic level, assuming the ten per cent law holds?

A The fourth trophic level will experience a delayed, but geometrically compounded, severe deficit in available energy.

B The fourth trophic level will independently generate its own energy to counteract the loss.

C The transfer efficiency will automatically increase to 50% to maintain apex predator biomass.

D The energy will start flowing backwards from the detritus food chain to sustain them.

💡 Short Explanation

10% law is multiplicative (exponential). GPP loss at the base compounds as it moves up. Apex predators feel the impact most severely.

✅ Correct Answer Explanation

Since each transfer is a 10% fraction (0.1ⁿ), any decrease in GPP (10,000 → 1,000) is amplified as you rise in trophic levels (Level 4: 0.001 × GPP). The deficit is "geometrically compounded" at higher levels.

❓ Why Other Options Are Incorrect

Option B, C, D → These are all thermodynamically impossible.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Showing how a base percentage decrease amplifies exponentially up the chain.

Final Logic: Compounding loss.

🧠 Memory Trick

"Base Loss = Apex Disaster."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Energy Transfer

CUET UG Biology Booster Test 3-Energy Flow and Trophic Levels

Test Complete!

Answer Review