Q.140 Botany ⭐ 360° Option Elimination Active

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NEET 2021 Botany Question 140 Solution

Topic: Biological Classification · Official NTA Booklet Code M1

Question

Which of the following statements is correct?

(1)Fusion of two cells is called Karyogamy.
(2)Fusion of protoplasms between two motile on non-motile gametes is called plasmogamy.
(3)Organisms that depend on living plants are called saprophytes.
(4)Some of the organisms can fix atmospheric nitrogen in specialized cells called sheath cells.

✓

Verified Against NTA Final Answer Key

Option (2) : Fusion of protoplasms between two motile on non-motile gametes is called plasmogamy.

📚 Biological Classification Easy

📋 Given Parameters & Problem Setup

Phenomenon Sexual reproduction in fungi & microbial definitions

Target Identify the statement that is CORRECT

⚡

The 30-Second Exam Hall Shortcut: ⚡ Plasmogamy = Protoplasm Fusion | Karyogamy = Nuclear Fusion

⏱️ Save ~20 seconds

The sexual cycle in fungi proceeds through three sequential stages: 1. Plasmogamy (fusion of protoplasms between two motile or non-motile gametes), 2. Karyogamy (fusion of two haploid nuclei), and 3. Meiosis in zygote! Statement (2) is verbatim NCERT text. Match Option (2)!

1 Check Statement (1): Fusion of two cells/nuclei is not karyogamy; karyogamy specifically means fusion of two nuclei

\implies

INCORRECT.

2 Check Statement (2): Fusion of protoplasms between two motile or non-motile gametes is called plasmogamy

\implies

CORRECT verbatim NCERT.

3 Check Statement (3): Organisms that depend on living plants are parasites, NOT saprophytes (saprophytes absorb nutrients from dead substrates)

\implies

INCORRECT.

4 Check Statement (4): Organisms fix nitrogen in specialized cells called heterocysts, NOT sheath cells

\implies

INCORRECT.

5 Match Option (2).

🛡️

Why You Can 100% Trust This Shortcut: Canonical NCERT Biological Classification on Kingdom Fungi Sexual Cycle.

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

The Tripartite Sexual Cycle in Fungi

In Kingdom Fungi, sexual reproduction involves three fundamental sequential events:

\begin{aligned} \mathbf{1.\text{ Plasmogamy:}} & \quad \mathbf{\text{Fusion of protoplasms between two motile or non-motile gametes}} \\[4pt] \text{\textbf{2. Karyogamy:}} & \quad \text{Fusion of the two compatible haploid nuclei } (n + n \to 2n) \\[4pt] \text{\textbf{3. Meiosis:}} & \quad \text{Reduction division in zygote resulting in haploid spores} \end{aligned}

Step 2

Evaluation and Refutation of Distractors

- Statement (1): Karyogamy refers strictly to the fusion of two nuclei ( $karyon$ = nucleus), not the fusion of entire vegetative cells. - Statement (3): Organisms that depend directly on living host plants are parasites; saprophytes feed strictly on dead, decaying organic matter. - Statement (4): Atmospheric nitrogen-fixing cyanobacteria (e.g., *Nostoc*, *Anabaena*) fix nitrogen in specialized thick-walled cells called heterocysts, not sheath cells (the gelatinous mucilaginous sheath simply protects the colony).

⭐

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:

Incorrect. Karyogamy is the fusion of two nuclei, whereas cell/protoplast fusion is plasmogamy.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing nuclear fusion (karyogamy) with protoplast fusion.

2 2

✓ 100% Correct

Verdict & Scientific Reason:

This statement is completely TRUE and represents the verbatim canonical NCERT definition of plasmogamy.

💡

Why this is airtight: None. Verbatim textbook definition.

3 3

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Organisms depending on living hosts are parasites; saprophytes absorb soluble organic matter from dead substrates.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing parasites with saprophytes.

4 4

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Nitrogen fixation takes place inside specialized cells called heterocysts.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing protective mucilaginous sheath with nitrogen-fixing heterocysts.

⚠️

NTA Trap Alert: Plasmogamy vs Karyogamy Root Confusion

"Plasma" = cytoplasm/protoplasm; "Karyon" = nucleus. Misreading these prefixes leads to selecting Statement (1).

🛡️ How to avoid the -1 mark: Remember: Plasmogamy = Protoplasm fusion; Karyogamy = Karyon (nuclear) fusion.

📖

Core NEET Syllabus Standard

NEET / NCERT Biology · Biological Classification Standard Benchmark

Core Scientific Principle Tested:

"The sexual cycle involves three steps: (i) Fusion of protoplasms between two motile or non-motile gametes called plasmogamy, (ii) Fusion of two nuclei called karyogamy, and (iii) Meiosis in zygote resulting in haploid spores."

Syllabus Focus: Kingdom Fungi: Reproduction

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

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NEET 2021 Botany Question 140 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Plasmogamy = Protoplasm Fusion | Karyogamy = Nuclear Fusion

Step-by-Step Rigorous Workflow & Mathematical Proof

The Tripartite Sexual Cycle in Fungi

Evaluation and Refutation of Distractors

360° Option Elimination Engine Key Feature

NTA Trap Alert: Plasmogamy vs Karyogamy Root Confusion

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Biological Classification

Symbiotic Mutualistic Association Between Algae and Fungi (Lichens)

Prions as Causative Agents of Bovine Spongiform Encephalopathy (Mad Cow Disease)

Morphological Shapes of Bacteria

Sequential Steps of the Fungi Sexual Reproduction Cycle

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