Q.183 Zoology ⭐ 360° Option Elimination Active

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NEET 2023 Zoology Question 183 Solution

Topic: Environmental Issues · Official NTA Booklet Code G5

Question

Which of the following statements is correct?

(1)Algal Bloom decreases fish mortality
(2)Eutrophication refers to increase in domestic sewage and waste water in lakes.
(3)Biomagnification refers to increase in concentration of the toxicant at successive trophic levels.
(4)Presence of large amount of nutrients in water restricts 'Algal Bloom'

✓

Verified Against NTA Final Answer Key

Option (3) : Biomagnification refers to increase in concentration of the toxicant at successive trophic levels.

📚 Environmental Issues Easy

📋 Given Parameters & Problem Setup

Topic Environmental pollution definitions

Task Identify the statement that is CORRECT

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The 30-Second Exam Hall Shortcut: ⚡ Biomagnification Definition Anchor

⏱️ Save ~20 seconds

Verbatim NCERT sentence under Biomagnification: "Biomagnification refers to increase in concentration of the toxicant at successive trophic levels." Instant 5-second answer matching Option (3)!

1 Option (1): Algal blooms increase (not decrease) fish mortality -> False.

2 Option (2): Eutrophication refers to nutrient enrichment aging of water body, not just sewage volume -> False.

3 Option (3): Biomagnification refers to increase in toxicant concentration at successive trophic levels -> Verbatim NCERT, Correct.

4 Option (4): Nutrients stimulate (not restrict) algal blooms -> False.

5 Match Option (3).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Environmental Issues ecotoxicology definitions.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Definition of Biological Biomagnification

Non-biodegradable lipophilic toxicants (such as DDT and mercury) cannot be metabolized or excreted by organisms and get passed to higher trophic levels, progressively concentrating up the food web:

\text{Water } (0.003\text{ ppb}) \xrightarrow{\text{Zooplankton}} \text{Small Fish} \xrightarrow{\text{Large Fish}} \text{Fish-eating Birds } (25\text{ ppm})

Step 2

Verbatim NCERT Reference

NCERT states verbatim: "Biomagnification refers to increase in concentration of the toxicant at successive trophic levels. This happens because a toxic substance accumulated by an organism cannot be metabolised or excreted, and is thus passed on to the next higher trophic level."

Step 3

Refutation of False Distractors

Algal blooms cause hypoxia that sharply *increases* fish mortality (ruling out Option 1). Eutrophication is the *natural or accelerated nutrient enrichment aging* of a lake (ruling out Option 2). High nutrients *stimulate* explosive algal blooms rather than restricting them (ruling out Option 4).

⭐

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:

Algal blooms deplete dissolved oxygen and secrete toxins, causing massive increases in fish mortality.

⚠️

Student Fallacy (Why candidates pick this trap): Inverting the lethal effect of eutrophic algal blooms on fish.

2 2

✗ Incorrect

Verdict & Scientific Reason:

Eutrophication is scientifically defined as the natural or cultural nutrient enrichment (aging) of a lake, not merely wastewater addition.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing the cause (sewage input) with the ecological definition (nutrient enrichment).

3 3

✓ 100% Correct

Verdict & Scientific Reason:

Matches NCERT verbatim as the definitive ecological principle of biomagnification.

💡

Why this is airtight: None; textbook verbatim precision.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Abundant nitrogen and phosphorus triggers and accelerates algal blooms, it never restricts them.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking excess nutrients somehow suppress algal growth.

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NTA Trap Alert: Eutrophication vs. Sewage Input Semantic Trap

Students frequently equate eutrophication simply with "pollution by sewage". NCERT rigorously defines eutrophication as the natural aging of a lake by nutrient enrichment.

🛡️ How to avoid the -1 mark: Look for the verbatim match: Biomagnification = increase in concentration of toxicant at successive trophic levels.

📖

Core NEET Syllabus Standard

NCERT Biology · Environmental Issues Standard Benchmark

Core Scientific Principle Tested:

"Biomagnification refers to increase in concentration of the toxicant at successive trophic levels."

Syllabus Focus: Biological Magnification

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Zoology Question 183 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Biomagnification Definition Anchor

Step-by-Step Rigorous Workflow & Mathematical Proof

Definition of Biological Biomagnification

Verbatim NCERT Reference

Refutation of False Distractors

360° Option Elimination Engine Key Feature

NTA Trap Alert: Eutrophication vs. Sewage Input Semantic Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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