CUET UG Biology Booster Test 2-Productivity and Decomposition Dynamics -

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CUET UG Biology Booster Test 2-Productivity and Decomposition Dynamics

⏱️ 30 Minutes

❓ 20 Questions

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

CUET UG Biology Booster Test 2-Productivity and Decomposition Dynamics

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QUESTION 1 OF 20

If two different types of ecosystems receive the same amount of solar input, their primary productivity will still vary. This is because primary productivity also depends on:

Answer Review

1 If two different types of ecosystems receive the same amount of solar input, their primary productivity will still vary. This is because primary productivity also depends on:

A The amount of detritus present in the soil

B The plant species inhabiting the area and their photosynthetic capacity

C The rate of secondary productivity by heterotrophs

D The number of tertiary consumers in the area

💡 Short Explanation

Primary productivity is a biological process. It depends on the efficiency of photosynthetic machinery. Environmental factors and species composition determine this capacity.

✅ Correct Answer Explanation

While solar energy is the energy source, primary productivity is fundamentally a biological process determined by the photosynthetic efficiency of the producer community. Different plant species have varying rates of carbon fixation, pigment content, and adaptations to their specific environment. Thus, productivity varies even with identical solar input.

❓ Why Other Options Are Incorrect

Option A → Incorrect; detritus relates to decomposition, not photosynthetic input.
Option C → Incorrect; secondary productivity is the result of primary production, not a cause.
Option D → Incorrect; tertiary consumers are at the top of the food chain and do not dictate the rate of photosynthesis.

🎯 Strategy

Used: Elimination

Application: Identifying that primary production is a "producer-driven" process eliminates consumer and decomposer factors.

Final Logic: Photosynthetic efficiency is a species-specific trait that determines productivity.

🧠 Memory Trick

"Species = Efficiency = Productivity."

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

2 Match the ecological expressions to what they accurately represent:

Column 1	Column 2
1. gm–2	P. Rate of biomass production in terms of weight
2. kcal m–2	Q. Biomass produced expressed in terms of energy
3. gm–2 yr–1	R. Rate of biomass production in terms of energy
4. (kcal m–2) yr–1	S. Biomass produced expressed in terms of weight

A 1-P, 2-R, 3-S, 4-Q

B 1-S, 2-Q, 3-P, 4-R

C 1-Q, 2-S, 3-R, 4-P

D 1-S, 2-P, 3-Q, 4-R

💡 Short Explanation

g m⁻² = Biomass (weight). kcal m⁻² = Energy. Adding yr⁻¹ turns a measurement into a rate.

✅ Correct Answer Explanation

1 (g m⁻²) represents biomass in weight (S). 2 (kcal m⁻²) represents biomass in energy (Q). 3 (g m⁻² yr⁻¹) is the rate of biomass production in weight (P). 4 (kcal m⁻² yr⁻¹) is the rate of biomass production in energy (R).

❓ Why Other Options Are Incorrect

Options A, C, and D mismatch the rate-based units with total biomass units.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Distinguishing between static units (m⁻²) and rate-based units (m⁻² yr⁻¹).

Final Logic: Addition of "yr" converts state to rate.

🧠 Memory Trick

"yr = Rate."

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

3 Which of the following is NOT a direct factor affecting the Gross Primary Productivity (GPP) of an ecosystem?

A Availability of nutrients

B Plant species inhabiting a particular area

C Rate of catabolism by soil fungi

D Photosynthetic capacity of plants

💡 Short Explanation

GPP is the output of producers (photosynthesis). Catabolism by fungi is part of decomposition. GPP occurs before decomposition even begins.

✅ Correct Answer Explanation

GPP is the total amount of organic matter synthesized by producers. Nutrients (A), species identity (B), and photosynthetic capacity (D) directly influence how well plants capture sunlight. Fungal catabolism (C) occurs after death (decomposition) and is unrelated to the initial synthesis of biomass by producers.

❓ Why Other Options Are Incorrect

Option A → Incorrect; nutrients limit photosynthesis.
Option B → Incorrect; plant type limits photosynthesis.
Option D → Incorrect; capacity limits photosynthesis.

🎯 Strategy

Used: Elimination

Application: Separating "Production" factors from "Decomposition" factors.

Final Logic: Fungi are decomposers; GPP is a producer process.

🧠 Memory Trick

"GPP = Plants; Catabolism = Fungi."

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

4 Which of the following statements about NPP are logically correct?
I. NPP is always less than GPP.
II. NPP represents the total solar energy fixed by producers without any deductions.
III. An increase in plant respiration rate, assuming constant GPP, will decrease NPP.
IV. NPP is only available to decomposers, not herbivores.

A I and III only

B I and II only

C II and IV only

D III and IV only

💡 Short Explanation

I: NPP = GPP - R. II: Incorrect, NPP is the net amount after respiration. III: NPP = GPP - R; higher R means lower NPP. IV: Incorrect, herbivores consume NPP too.

✅ Correct Answer Explanation

Statement I is true because GPP is the total and R is always a positive value subtracted from it. Statement III is true because the formula NPP = GPP - R dictates that as R increases, NPP decreases. Statement II describes GPP, not NPP. Statement IV is incorrect as herbivores are primary consumers of NPP.

❓ Why Other Options Are Incorrect

Option B → Incorrect as statement II defines GPP.
Option C → Incorrect as statements II and IV are false.
Option D → Incorrect as statement IV is false.

🎯 Strategy

Used: Elimination

Application: Testing the formula GPP - R = NPP against the statements.

Final Logic: Mathematically, NPP is GPP minus respiration.

🧠 Memory Trick

"Net = Gross - Respiration."

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

5 In the calculation GPP - R = NPP, the 'R' represents respiration losses. Ecologically, this 'R' implies that:

A Plants use a considerable amount of organic matter to sustain their own metabolic needs.

B Herbivores consume a large fraction of the gross production.

C Energy is lost as heat directly from the sun before reaching plants.

D Decomposers respire heavily during fragmentation.

💡 Short Explanation

R = Plant respiration. It is a metabolic cost of living. It is an internal loss, not an external one (like herbivory).

✅ Correct Answer Explanation

The term 'R' in the ecosystem equation stands for the energy utilized by plants during cellular respiration to maintain their cellular functions. This is a cost paid by the producer to survive and grow. Option B is external consumption, and C/D are unrelated to plant-level respiration.

❓ Why Other Options Are Incorrect

Option B → Incorrect; this is herbivory, not plant respiration.
Option C → Incorrect; this is thermodynamic inefficiency of the sun, not plant respiration.
Option D → Incorrect; this is decomposition respiration.

🎯 Strategy

Used: Substitution

Application: Replacing "R" with its definition "Plant Respiration."

Final Logic: Respiration = Self-maintenance metabolism.

🧠 Memory Trick

"R = Respiration = Self-maintenance."

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

6 Why is NPP specifically referred to as the "available biomass"?

A It is the total biomass generated before the plants use any for themselves.

B It is the exact biomass that decomposers turn into humus.

C It represents the net organic matter left over to sustain the next trophic levels (heterotrophs).

D It is the biomass that remains after leaching has occurred.

💡 Short Explanation

"Available" refers to consumers. Producers have already taken their "cut" (Respiration). NPP is the surplus.

✅ Correct Answer Explanation

NPP is the energy left in the plant biomass after the plant has satisfied its own respiratory requirements. Because this biomass is essentially "surplus" energy, it is the only portion available for primary consumers (herbivores) and other heterotrophs.

❓ Why Other Options Are Incorrect

Option A → Incorrect; this defines GPP.
Option B → Incorrect; decomposers also consume living tissue and other forms.
Option D → Incorrect; leaching is a separate soil process.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Matching "Available" to "Next trophic levels."

Final Logic: NPP = Surplus for the food chain.

🧠 Memory Trick

"Available = Surplus = Net."

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

7 Secondary productivity is NOT associated with the metabolic activities of:

A Primary consumers

B Secondary consumers

C Heterotrophs

D Photosynthetic algae

💡 Short Explanation

Secondary productivity = Consumers (Heterotrophs). Algae = Producers (Autotrophs). Autotrophs perform Primary productivity.

✅ Correct Answer Explanation

Secondary productivity is the rate of new organic matter formation by consumers (heterotrophs). Since photosynthetic algae are autotrophs (producers), their activity is associated with primary productivity, not secondary.

❓ Why Other Options Are Incorrect

Option A → Incorrect; these are heterotrophs.
Option B → Incorrect; these are heterotrophs.
Option C → Incorrect; all heterotrophs are involved in secondary production.

🎯 Strategy

Used: Odd One Out

Application: Differentiating between autotrophs (Primary) and heterotrophs (Secondary).

Final Logic: Algae = Producer = Primary Productivity.

🧠 Memory Trick

"Secondary = Consumer = NOT Algae."

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

8 Arrange the flow and transformation of organic matter/energy in an ecosystem sequentially:
1. Net Primary Productivity (NPP)
2. Solar energy input
3. Secondary Productivity
4. Gross Primary Productivity (GPP)

A 4 → 2 → 1 → 3

B 2 → 1 → 4 → 3

C 2 → 4 → 1 → 3

D 2 → 4 → 3 → 1

💡 Short Explanation

2 (Solar input) triggers 4 (GPP). 4 - R = 1 (NPP). 1 supports 3 (Secondary production).

✅ Correct Answer Explanation

The correct flow is Solar Input → GPP (fixed) → NPP (fixed minus respiration) → Secondary Productivity (consumer utilization of NPP).

❓ Why Other Options Are Incorrect

Other sequences suggest Secondary production happens before NPP, which is biologically impossible.

🎯 Strategy

Used: Substitution

Application: Tracing the energy path: Sun to Producer (GPP) to Surplus (NPP) to Consumer (Secondary).

Final Logic: Energy flows from source to producer surplus to consumer.

🧠 Memory Trick

"Solar-Gross-Net-Consumer."

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

9 Out of the 170 billion tons of total global NPP, oceans contribute only 55 billion tons despite occupying 70% of the surface. This paradox indicates that:

A Oceanic plants have no respiration losses.

B The rate of secondary productivity in oceans is higher than terrestrial ecosystems.

C Terrestrial ecosystems have significantly higher productivity per unit area than oceans.

D Oceanic detritus limits photosynthetic light.

💡 Short Explanation

Area: 30% (Land) vs 70% (Ocean). Output: 115 (Land) vs 55 (Ocean). Conclusion: Land is much more productive per unit.

✅ Correct Answer Explanation

Because land occupies only 30% of the Earth but produces 115 billion tons, while oceans occupy 70% but produce only 55 billion, it mathematically implies that land-based ecosystems are far more productive per unit area than oceanic ecosystems.

❓ Why Other Options Are Incorrect

Option A → Incorrect; all living things respire.
Option B → Incorrect; this does not explain the GPP/NPP total.
Option D → Incorrect; this is a hypothesis, not the primary logical deduction.

🎯 Strategy

Used: Dimensional/Unit Analysis

Application: Comparing percentage of area vs. total productivity values to determine yield per area.

Final Logic: Higher productivity in a smaller area = higher density of production.

🧠 Memory Trick

"Land = Small Area, Big Output; Ocean = Big Area, Small Output."

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

10 Match the productivity figures to their respective domains:

Column 1	Column 2
1. 170 billion tons	P. NPP of the oceans
2. 55 billion tons	Q. Area of the Earth's surface occupied by oceans
3. 115 billion tons	R. Annual NPP of the whole biosphere
4. 70 percent	S. NPP of the land (terrestrial ecosystems)

A 1-R, 2-S, 3-P, 4-Q

B 1-R, 2-P, 3-S, 4-Q

C 1-P, 2-R, 3-Q, 4-S

D 1-S, 2-Q, 3-P, 4-R

💡 Short Explanation

170 = Total (R). 55 = Ocean (P). 115 = Land (S). 70% = Ocean Area (Q).

✅ Correct Answer Explanation

The correct values are: 170 (Total Biosphere) = R; 55 (Ocean) = P; 115 (Land) = S; 70% (Ocean Area) = Q.

❓ Why Other Options Are Incorrect

Options A, C, and D incorrectly assign the values to the wrong categories.

🎯 Strategy

Used: Recall

Application: Recalling NCERT statistics for biosphere productivity.

Final Logic: Match specific values to established ecological facts.

🧠 Memory Trick

"Total 170, Land 115, Sea 55."

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

11 Decomposition is an essential ecosystem function. Which of the following is NOT a characteristic of this process?

A Breakdown of complex organic matter into inorganic substances

B Utilisation of detritus as a raw material

C Release of nutrients back into the ecosystem

D Conversion of inorganic materials into organic biomass

💡 Short Explanation

Decomposition is a degradative process, not a constructive one. Option D defines primary productivity (photosynthesis). Decomposition converts organic into inorganic, not vice versa.

✅ Correct Answer Explanation

Decomposition is the process of breaking down organic matter (detritus) into simple inorganic substances (mineralisation). Converting inorganic materials into organic biomass is the definition of photosynthesis/primary productivity. Thus, Option D is not a characteristic of decomposition.

❓ Why Other Options Are Incorrect

Option A → Incorrect; this is the primary definition of decomposition.
Option B → Incorrect; detritus is the substrate for decomposition.
Option C → Incorrect; nutrient release (mineralisation) is the final phase of decomposition.

🎯 Strategy

Used: Elimination

Application: Identifying the functional mismatch between "degradation" (decomposition) and "production" (photosynthesis).

Final Logic: Decomposition is destructive/reductive, not constructive.

🧠 Memory Trick

"Decomposition = Inorganic end; Production = Organic end."

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

12 Which of the following correctly identify the composition of detritus?
I. Dead plant remains such as leaves and bark.
II. Living phytoplankton in a pond.
III. Fecal matter of animals.
IV. The inorganic salts precipitated in the soil horizon.

A I and III only

B I and II only

C II and IV only

D III and IV only

💡 Short Explanation

Detritus = dead organic matter + waste. I is correct (plant remains). II is incorrect (living). III is correct (waste). IV is incorrect (inorganic salts).

✅ Correct Answer Explanation

Detritus is defined as non-living organic matter. Dead plant remains (I) and fecal matter (III) are both organic and dead, fitting the definition. Phytoplankton (II) are living, and inorganic salts (IV) are mineral, not organic matter.

❓ Why Other Options Are Incorrect

Option B → Incorrect; II is living.
Option C → Incorrect; II is living, IV is inorganic.
Option D → Incorrect; IV is inorganic.

🎯 Strategy

Used: Extreme Word Filter

Application: Filtering for "Dead" and "Organic" identifies the correct items (I and III).

Final Logic: Detritus must be both dead and organic.

🧠 Memory Trick

"Dead + Organic = Detritus."

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

📄 Passage

"Humification and mineralisation occur during decomposition in the soil. Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients."

Based on the passage, the extremely slow rate of humus decomposition is primarily due to its:

A Colloidal nature

B High resistance to microbial action

C Dark colour

D Ability to undergo mineralisation

💡 Short Explanation

Humus is chemically complex. This structure resists enzymatic attack by microbes. Hence, decomposition is slow.

✅ Correct Answer Explanation

The passage explicitly states that humus is "highly resistant to microbial action and undergoes decomposition at an extremely slow rate." This resistance is the primary driver for the slow turnover of humus.

❓ Why Other Options Are Incorrect

Option A → Incorrect; being colloidal makes it a nutrient reservoir, not slow to decompose.
Option C → Incorrect; color is a physical trait unrelated to rate.
Option D → Incorrect; mineralisation is the process that occurs after/during the slow degradation.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Directly referencing the cause-effect relationship described in the provided passage.

Final Logic: Resistance to microbes directly causes slow decomposition.

🧠 Memory Trick

"Resistance = Slow rate."

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

📄 Passage

What specific physical property allows humus to act effectively as a nutrient reservoir?

A It is colloidal in nature

B It is highly resistant

C It is amorphous

D It is water-soluble

💡 Short Explanation

Colloids have large surface areas. This allows adsorption of nutrients. Hence, it acts as a reservoir.

✅ Correct Answer Explanation

The passage states, "Being colloidal in nature it serves as a reservoir of nutrients." Colloidal particles are physically suited for adsorbing charged nutrients, preventing them from washing away and keeping them available.

❓ Why Other Options Are Incorrect

Option B → Incorrect; resistance relates to decomposition rate, not storage.
Option C → Incorrect; amorphous shape is not the driver for nutrient storage.
Option D → Incorrect; humus is largely insoluble.

🎯 Strategy

Used: Substitution

Application: Using the text directly to link "colloidal" to "nutrient reservoir."

Final Logic: Colloid = High surface area = Nutrient storage.

🧠 Memory Trick

"Colloidal = Storage."

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

15 The fragmentation of detritus by earthworms primarily aids the overall decomposition process by:

A Releasing inorganic nutrients directly into the air

B Breaking down detritus into smaller particles, thereby increasing the surface area for microbial enzymes

C Precipitating water-soluble salts deep in the soil

D Converting humus into inorganic nutrients

💡 Short Explanation

Enzymes work on surfaces. Smaller particles = More surface area. More area = Faster enzymatic action (Catabolism).

✅ Correct Answer Explanation

Fragmentation increases the surface area of detritus. Since microbial catabolism (chemical decomposition) is an enzymatic process that acts on the surface of organic particles, more surface area allows for significantly faster and more efficient enzyme interaction.

❓ Why Other Options Are Incorrect

Option A → Incorrect; nutrients are released in soil, not air.
Option C → Incorrect; this is leaching.
Option D → Incorrect; this is mineralisation.

🎯 Strategy

Used: Elimination

Application: Focusing on the primary purpose of fragmentation: facilitating the next step (Catabolism).

Final Logic: Fragmentation = Surface Area = Microbial Efficiency.

🧠 Memory Trick

"Smaller pieces = More surface = Faster enzymes."

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

16 Which of the following is NOT a consequence of the leaching process during decomposition?

A Downward movement of water-soluble nutrients

B Precipitation of nutrients in the soil horizon

C Nutrients becoming unavailable as salts

D Conversion of detritus into dark amorphous humus

💡 Short Explanation

Leaching is a physical transport process. Humification (Option D) is a separate chemical/biological process. Leaching and humification are distinct.

✅ Correct Answer Explanation

Leaching involves the downward movement and precipitation of inorganic nutrients. Humification is the formation of humus, which is a complex biochemical process. Leaching does not convert detritus into humus.

❓ Why Other Options Are Incorrect

Option A → Incorrect; this is the definition of leaching.
Option B → Incorrect; this is a consequence of leaching.
Option C → Incorrect; this is a consequence of leaching.

🎯 Strategy

Used: Odd One Out

Application: Identifying "Humification" as a different stage of decomposition compared to "Leaching."

Final Logic: Leaching ≠ Humification.

🧠 Memory Trick

"Leaching = Moving; Humification = Changing."

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

17 Arrange the environmental conditions according to how they favor the catabolic steps of decomposition, from most favorable to most inhibitory:
1. Warm environment
2. Moist environment
3. Low temperature
4. Anaerobiosis

A 1 and 2 (favour) → 3 and 4 (inhibit)

B 3 and 4 (favour) → 1 and 2 (inhibit)

C 4 and 1 (favour) → 2 and 3 (inhibit)

D 2 and 4 (favour) → 1 and 3 (inhibit)

💡 Short Explanation

Microbes thrive in warm, moist (aerobic) conditions. Cold or lack of oxygen (anaerobiosis) slows down enzymatic activity.

✅ Correct Answer Explanation

Catabolism is an enzymatic process. Enzymes work optimally in warm and moist conditions (1 and 2). Low temperature (3) reduces metabolic speed, and anaerobiosis (4) limits the oxidative power of most decomposers. Thus, 1 and 2 favor, while 3 and 4 inhibit.

❓ Why Other Options Are Incorrect

Other sequences misclassify the impact of environmental conditions on microbial enzymatic rates.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Recalling the "optimal" vs. "stressful" conditions for decomposer microbes.

Final Logic: Enzymes love warmth/moisture; they hate cold/anaerobic.

🧠 Memory Trick

"Warm+Moist = Fast; Cold+Airless = Slow."

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

18 While catabolism uses bacterial enzymes to degrade detritus, the later step of mineralisation relies on microbes to further degrade:

A Fresh detritus

B Humus

C Living autotrophs

D Precipitated salts

💡 Short Explanation

Humus is the final accumulation. Mineralisation releases minerals from this humus. Therefore, microbes must degrade the humus itself.

✅ Correct Answer Explanation

Mineralisation is the process by which inorganic nutrients are released from the humus. For this to occur, microbes must decompose the humus to liberate the trapped minerals. Fresh detritus is catabolized first; humus is the secondary substrate for final mineralisation.

❓ Why Other Options Are Incorrect

Option A → Incorrect; catabolism acts on fresh detritus.
Option C → Incorrect; microbes do not decompose living autotrophs.
Option D → Incorrect; salts are the product of mineralisation, not the substrate.

🎯 Strategy

Used: Substitution

Application: Linking "mineralisation" to the "release from humus."

Final Logic: Mineralisation = Breaking down Humus.

🧠 Memory Trick

"Humus breakdown = Mineralisation."

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

19 If a soil environment becomes waterlogged and anaerobic (lacking oxygen), what is the most likely consequence for the decomposition cycle?

A Decomposition will be inhibited, resulting in a build-up of organic materials.

B The rate of humification will immediately increase.

C Leaching will accelerate, providing more available salts.

D Bacterial enzymes will catabolize detritus faster.

💡 Short Explanation

Decomposition requires oxygen. No oxygen = Slow/No decomposition. Materials accumulate (peat/muck).

✅ Correct Answer Explanation

Most decomposers are aerobic. In waterlogged/anaerobic conditions, they cannot thrive, and enzymatic rates drop. Since decomposition slows down, organic materials cannot be broken down and start to accumulate in the soil.

❓ Why Other Options Are Incorrect

Option B → Incorrect; humification also requires microbial action.
Option C → Incorrect; leaching is restricted in waterlogged, stagnant conditions.
Option D → Incorrect; anaerobic conditions slow down catabolism.

🎯 Strategy

Used: Elimination

Application: Knowing that oxygen is the "decomposer fuel," its absence logically leads to system slowing (A).

Final Logic: Anaerobic = No fuel = No breakdown = Accumulation.

🧠 Memory Trick

"Waterlogged = No Air = No Decomposition."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Factors affecting Decomposition

20 A researcher compares two types of leaf litter. Leaf A is rich in lignin and chitin, while Leaf B is rich in nitrogen and sugars. Under identical climatic conditions:

A Leaf A will decompose quicker than Leaf B

B Both leaves will decompose at the exact same rate

C Leaf B will decompose quicker than Leaf A

D Leaf B will bypass fragmentation and directly undergo leaching

💡 Short Explanation

Nitrogen + Sugars = Easy food. Lignin + Chitin = Hard/Tough. Easy food = Fast decay.

✅ Correct Answer Explanation

Decomposition rates are determined by chemical quality. High nitrogen and sugars are readily available for microbial uptake (fast). Lignin and chitin are highly complex and recalcitrant, requiring specialized enzymes and much more time (slow).

❓ Why Other Options Are Incorrect

Option A → Incorrect; lignin/chitin is the slowest combination.
Option B → Incorrect; composition is the primary factor.
Option D → Incorrect; fragmentation is a standard step.

🎯 Strategy

Used: Contextual/Tonal Matching

Application: Comparing "High Quality" (N+Sugar) vs "Low Quality" (Lignin+Chitin) substrate.

Final Logic: Simple molecules = Fast microbial degradation.

🧠 Memory Trick

"Sweet & Nitrogen = Fast; Tough (Lignin) = Slow."

📚 Class XII – Biology – Chapter: Ecosystem – Topic: Factors affecting Decomposition

CUET UG Biology Booster Test 2-Productivity and Decomposition Dynamics

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