Q.149 Botany ⭐ 360° Option Elimination Active

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NEET 2023 Botany Question 149 Solution

Topic: Environmental Issues · Official NTA Booklet Code G5

Question

Which one of the following statements is NOT correct?

(1)The amount of some toxic substances of industrial waste water increases in the organisms at successive trophic levels.
(2)The micro-organisms involved in biodegradation of organic matter in a sewage polluted water body consume a lot of oxygen causing the death of aquatic organisms.
(3)Algal blooms caused by excess of organic matter in water improve water quality and promote fisheries.
(4)Water hyacinth grows abundantly in eutrophic water bodies and leads to an imbalance in the ecosystem dynamics of the water body.

✓

Verified Against NTA Final Answer Key

Option (3) : Algal blooms caused by excess of organic matter in water improve water quality and promote fisheries.

📚 Environmental Issues Easy

📋 Given Parameters & Problem Setup

Topic Water pollution and ecological consequences

Task Identify the statement that is NOT correct (incorrect)

⚡

The 30-Second Exam Hall Shortcut: ⚡ Negative Question Trap: Algal Blooms HARM Water & Kill Fish!

⏱️ Save ~20 seconds

The question asks for the statement that is NOT correct. Statement (3) claims algal blooms "improve water quality and promote fisheries". Algal blooms cause severe water deterioration, oxygen depletion, toxin secretion, and massive fish kills! Statement (3) is false and the correct answer!

1 Statement (1): Biomagnification causes increase in toxic substances at higher trophic levels -> Correct statement.

2 Statement (2): Microorganisms decomposing organic sewage consume dissolved O2 causing death of aquatic life -> Correct statement.

3 Statement (3): Algal blooms improve water quality and promote fisheries -> Blatantly False statement.

4 Statement (4): Water hyacinth (Eichhornia) thrives in eutrophic waters and disrupts ecosystem dynamics -> Correct statement.

5 Since (3) is false, select Option (3).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Environmental Issues aquatic eutrophication impact facts.

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Pathophysiology of Algal Blooms

Runoff of domestic sewage and agricultural fertilizers introduces excessive nitrogen and phosphorus into water bodies (cultural eutrophication), inducing explosive proliferation of planktonic algae:

\text{Excess Inorganic Nutrients (N, P)} \longrightarrow \text{Algal Bloom} \implies \begin{cases} \text{Depletes Dissolved Oxygen (DO } \downarrow) \\[3pt] \text{Imparts foul odor and taste} \\[3pt] \text{Secretes potent cyanotoxins} \\[3pt] \mathbf{\text{Causes massive fish mortality}} \end{cases}

Step 2

Verbatim NCERT Reference

NCERT states verbatim: "Presence of large amounts of nutrients in waters also causes excessive growth of planktonic (free-floating) algae, called an algal bloom. Algal blooms impart a distinct colour to the water bodies. Algal blooms cause deterioration of the water quality and fish mortality. Some bloom-forming algae are extremely toxic to human beings and animals."

Step 3

Evaluation of Other Statements

Statement (1) accurately defines biomagnification (e.g., DDT and mercury). Statement (2) accurately describes biochemical oxygen demand (BOD) and suffocating hypoxia. Statement (4) accurately describes the "Terror of Bengal" ( $\textit{Eichhornia crassipes}$ ).

⭐

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:

This statement is scientifically true (biomagnification); hence not the incorrect option sought.

⚠️

Student Fallacy (Why candidates pick this trap): Selecting a true statement without noticing the negative prompt "NOT correct".

2 2

✗ Incorrect

Verdict & Scientific Reason:

This statement is factually true (BOD spike causing hypoxia); hence not the incorrect option.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing high BOD impact with incorrect statement.

3 3

✓ 100% Correct

Verdict & Scientific Reason:

This statement is completely false (algal blooms severely deteriorate water quality and kill fish), making it the correct answer to the negative prompt.

💡

Why this is airtight: None; identifies the blatantly false claim.

4 4

✗ Incorrect

Verdict & Scientific Reason:

This statement is factually true (Eichhornia chokes eutrophic waters); hence not the incorrect option.

⚠️

Student Fallacy (Why candidates pick this trap): Failing to eliminate the true invasive plant statement.

⚠️

NTA Trap Alert: Negative Query "NOT Correct" Overlook Trap

Students reading too fast miss the capitalized "NOT correct" and select Option (1) because it is a true textbook fact about biomagnification.

🛡️ How to avoid the -1 mark: Always circle "NOT correct" in the question stem and actively hunt for the false statement.

📖

Core NEET Syllabus Standard

NCERT Biology · Environmental Issues Standard Benchmark

Core Scientific Principle Tested:

"Algal blooms cause deterioration of the water quality and fish mortality. Some bloom-forming algae are extremely toxic."

Syllabus Focus: Water Pollution and Its Control

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2023 Botany Question 149 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Negative Question Trap: Algal Blooms HARM Water & Kill Fish!

Step-by-Step Rigorous Workflow & Mathematical Proof

Pathophysiology of Algal Blooms

Verbatim NCERT Reference

Evaluation of Other Statements

360° Option Elimination Engine Key Feature

NTA Trap Alert: Negative Query "NOT Correct" Overlook Trap

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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