Q.154 Zoology ⭐ 360° Option Elimination Active

NEET 2025 Zoology Question 154 Solution

Topic: Sexual Reproduction in Flowering Plants · Official NTA Booklet Code 45

Question

How many meiotic and mitotic divisions need to occur for the development of a mature female gametophyte from the megaspore mother cell in an angiosperm plant?

(1)2 Meiosis and 3 Mitosis
(2)1 Meiosis and 2 Mitosis
(3)1 Meiosis and 3 Mitosis
(4)No Meiosis and 2 Mitosis

✓

Verified Against NTA Final Answer Key

Option (3) : 1 Meiosis and 3 Mitosis

📚 Sexual Reproduction in Flowering Plants Easy

📋 Given Parameters & Problem Setup

Starting Cell Megaspore mother cell (MMC, diploid 2n)

End Product Mature female gametophyte / embryo sac (7-celled, 8-nucleate)

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The 30-Second Exam Hall Shortcut: ⚡ Embryo Sac Division Math Fingerprint

⏱️ Save ~25 seconds

MMC (2n) undergoes 1 MEIOSIS -> 4 megaspores (3 degenerate, 1 functional); 1 functional megaspore undergoes 3 MITOSES (1->2->4->8 nuclei) -> 7-celled embryo sac! Exactly 1 Meiosis and 3 Mitosis!

1 Count the cell divisions step-by-step from NCERT Section 2.2.2:

2 Diploid MMC (2n) undergoes MEIOSIS to form a linear tetrad of 4 haploid megaspores (n). -> Count: 1 Meiosis.

3 Three micropylar megaspores degenerate, leaving 1 functional chalazal megaspore.

4 Functional megaspore nucleus divides mitotically: 1 -> 2 nuclei (Mitosis 1).

5 The 2 nuclei divide mitotically: 2 -> 4 nuclei (Mitosis 2).

6 The 4 nuclei divide mitotically: 4 -> 8 nuclei (Mitosis 3).

7 Total: 1 Meiosis + 3 Mitosis!

8 Select Option (3) 1 Meiosis and 3 Mitosis!

🛡️

Why You Can 100% Trust This Shortcut: Outbreeding Devices in Angiosperms (NCERT Biology · Sexual Reproduction in Flowering Plants: Self-incompatibility and dichogamy).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Megasporogenesis (Meiotic Phase)

The process of formation of megaspores from the megaspore mother cell is called megasporogenesis:

• A single diploid megaspore mother cell (MMC) differentiates in the micropylar region of the nucellus.
• The MMC undergoes a single meiotic division (1 Meiosis) to produce a linear tetrad of four haploid megaspores.
• In a majority of angiosperms (monosporic development), three megaspores at the micropylar end degenerate, and only one functional megaspore (chalazal) develops into the female gametophyte.

Step 2

Megagametogenesis (Mitotic Phase)

Development of the female gametophyte from the functional megaspore:

• Mitosis 1: The nucleus of the functional megaspore divides mitotically to form two nuclei, which move to the opposite poles, forming the 2-nucleate embryo sac.
• Mitosis 2: Another mitotic division results in the formation of the 4-nucleate embryo sac.
• Mitosis 3: A third mitotic division leads to the formation of the 8-nucleate stage of the embryo sac.
• Total mitotic divisions = 3 Mitosis (free nuclear).

Step 3

Conclusion

The complete development of a mature female gametophyte from an MMC requires precisely 1 Meiotic division followed by 3 Mitotic divisions.

\text{MMC (2n)} \xrightarrow{1\text{ Meiosis}} 1\text{ Megaspore (n)} \xrightarrow{3\text{ Mitoses}} \text{Embryo Sac (8-nucleate)}

⭐

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 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. An MMC undergoes only one meiotic division, never two.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing Meiosis I and Meiosis II as two separate full meioses.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. 2 mitoses would yield only 4 nuclei, whereas the mature embryo sac requires 8 nuclei.

⚠️

Student Fallacy (Why candidates pick this trap): Under-counting mitotic cycles (

2^2 = 4 \neq 8

3 C

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. Exactly matches the monosporic developmental sequence: 1 meiosis to form megaspores + 3 free nuclear mitoses to generate 8 nuclei.

💡

Why this is airtight: None; pristine botanical math.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Omits meiosis entirely, which would fail to reduce ploidy.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing gametophyte development with vegetative apomixis.

⚠️

NTA Trap Alert: Embryo Sac (Female) vs Pollen Grain (Male) Divisions

To form a mature pollen grain from a Microspore Mother Cell: 1 Meiosis + 2 Mitosis (yielding 3-celled pollen). To form a mature Embryo Sac from MMC: 1 Meiosis + 3 Mitosis (yielding 8-nucleate embryo sac)!

🛡️ How to avoid the -1 mark: Female gametophyte needs 8 nuclei (

2^3

), so it takes 3 MITOSES!

📖

Core NEET Syllabus Standard

NEET Biology Core Syllabus · Sexual Reproduction in Flowering Plants Standard Benchmark

Core Scientific Principle Tested:

"Development of an 8-nucleate monosporic embryo sac from an MMC requires 1 meiotic and 3 mitotic divisions."

Syllabus Focus: Megasporogenesis & Development of Female Gametophyte

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

1 Meiosis makes the Spore, 3 Mitoses build the Embryo Sac door (2³ = 8 nuclei)!

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NEET 2025 Zoology Question 154 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Embryo Sac Division Math Fingerprint

Step-by-Step Rigorous Workflow & Mathematical Proof

Megasporogenesis (Meiotic Phase)

Megagametogenesis (Mitotic Phase)

Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Embryo Sac (Female) vs Pollen Grain (Male) Divisions

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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