Q.122 Botany ⭐ 360° Option Elimination Active

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NEET 2021 Botany Question 122 Solution

Topic: Ecosystem · Official NTA Booklet Code M1

Question

In the equation GPP − R = NPP, R represents:

✓

Verified Against NTA Final Answer Key

Option (4) : Respiration losses

📚 Ecosystem Easy

📋 Given Parameters & Problem Setup

Ecological Equation GPP - R = NPP

Target Variable Physical meaning of term R

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The 30-Second Exam Hall Shortcut: ⚡ R = Respiration Loss in Ecosystem Productivity

⏱️ Save ~15 seconds

Gross Primary Productivity (GPP) is the total rate of organic matter production. A fraction of GPP is metabolized by autotrophs during respiration ( $R$ ). The remaining biomass available to heterotrophs is Net Primary Productivity ( $NPP = GPP - R$ ). Thus, $R$ = Respiration losses! Match Option (4)!

GPP

= Gross Primary Productivity (total rate of photosynthetic synthesis).

2 Autotrophs consume energy for cellular respiration (

R

NPP

= Net Primary Productivity (accumulated biomass available to herbivores).

4 Equation:

GPP - R = NPP \implies R

represents Respiration losses.

5 Match Option (4).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Ecosystem principles on Energy Flow and Productivity.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Definition of Ecosystem Productivity Terms

Primary productivity is partitioned into gross and net components depending on metabolic expenditure:

\begin{aligned} \text{\textbf{GPP (Gross Primary Productivity):}} & \quad \text{Total organic matter synthesized during photosynthesis} \\[4pt] \mathbf{R} & \quad \mathbf{\text{Respiration losses by primary producers}} \\[4pt] \text{\textbf{NPP (Net Primary Productivity):}} & \quad \text{Biomass available for consumption by heterotrophs} \end{aligned}

Step 2

Algebraic Relationship

The fundamental balance equation is:

\mathbf{GPP - R = NPP} \iff \mathbf{R = GPP - NPP}

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 1

✗ Incorrect

Verdict & Scientific Reason:

Radiant energy is the incoming solar flux (PAR), not the subtracted variable R.

⚠️

Student Fallacy (Why candidates pick this trap): Associating "R" with radiation/radiant energy.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Retardation factor ( $R_f$ ) is an analytical chemistry parameter in chromatography, completely irrelevant to ecosystem energetics.

⚠️

Student Fallacy (Why candidates pick this trap): Importing terminology from organic chemistry chromatography.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Environmental factors regulate GPP rates, but R specifically denotes metabolic respiratory loss.

⚠️

Student Fallacy (Why candidates pick this trap): Vague conceptual guessing.

4 4

✓ 100% Correct

Verdict & Scientific Reason:

In the productivity equation, R specifically stands for respiratory losses incurred by producers.

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Why this is airtight: None. Direct textbook formula definition.

⚠️

NTA Trap Alert: Mnemonic Confusion: Radiant Energy vs Respiration Loss

Under exam pressure, students who see the letter "R" in an energy equation instinctively think of "Radiation" or "Radiant energy" rather than "Respiration".

🛡️ How to avoid the -1 mark: Remember: Plants respire to stay alive;

R

is the respiration tax deducted from gross photosynthetic profit.

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Core NEET Syllabus Standard

NEET / NCERT Biology · Ecosystem Standard Benchmark

Core Scientific Principle Tested:

"A considerable amount of GPP is utilized by plants in respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP)."

Syllabus Focus: Productivity: Gross and Net Primary Productivity

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2021 Botany Question 122 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ R = Respiration Loss in Ecosystem Productivity

Step-by-Step Rigorous Workflow & Mathematical Proof

Definition of Ecosystem Productivity Terms

Algebraic Relationship

360° Option Elimination Engine Key Feature

NTA Trap Alert: Mnemonic Confusion: Radiant Energy vs Respiration Loss

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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