HS II Sexual Reproduction Questions with answer

Multiple Choice Questions (MCQs)

1. The gynoecium represents:
A. Male reproductive part
B. Female reproductive part
C. Sterile part
D. Accessory organ
Answer: B

2. A flower with fused carpels is called:
A. Apocarpous
B. Syncarpous
C. Monocarpellary
D. Bisexual
Answer: B

3. The part of pistil that receives pollen grains is:
A. Style
B. Ovary
C. Stigma
D. Placenta
Answer: C

4. The ovules are attached to:
A. Style
B. Stigma
C. Placenta
D. Micropyle
Answer: C

5. The opening in the ovule through which pollen tube enters is:
A. Hilum
B. Chalaza
C. Micropyle
D. Nucellus
Answer: C

6. Megasporogenesis involves:
A. Mitosis
B. Meiosis
C. Fertilization
D. Pollination
Answer: B

7. Number of megaspores formed after meiosis of MMC:
A. 2
B. 3
C. 4
D. 8
Answer: C

8. Typical angiosperm embryo sac is:
A. 8-celled, 7-nucleate
B. 7-celled, 8-nucleate
C. 6-celled, 8-nucleate
D. 8-celled, 8-nucleate
Answer: B

9. The synergids are located at:
A. Chalazal end
B. Micropylar end
C. Center
D. Nucellus
Answer: B

10. Cells present at chalazal end are:
A. Synergids
B. Egg cell
C. Antipodals
D. Polar nuclei
Answer: C

11. During monosporic development, the embryo sac develops from:

A. All four megaspores
B. Two megaspores
C. One functional megaspore
D. Megaspore mother cell directly

Answer: C

12. Free nuclear divisions in embryo sac formation imply:

A. Cytokinesis occurs before mitosis
B. Nuclear division without cell wall formation
C. Only one nucleus divides
D. Meiosis without cytokinesis

Answer: B

13. Which structure is directly responsible for guiding pollen tube?

A. Egg cell
B. Antipodals
C. Synergids
D. Polar nuclei

Answer: C

14. If the MMC fails to undergo meiosis, the resulting embryo sac would be:

A. Haploid
B. Diploid
C. Triploid
D. Sterile only

Answer: B

15. Which of the following correctly represents the sequence?

A. MMC → Megaspore → Embryo sac → Ovule
B. Ovule → MMC → Megaspore → Embryo sac
C. MMC → Ovule → Embryo sac → Megaspore
D. Megaspore → MMC → Ovule → Embryo sac

Answer: B

16. The central cell becomes triploid after:

A. Syngamy
B. Double fertilization
C. Triple fusion
D. Pollination

Answer: C

17. Which of the following is NOT haploid?

A. Egg cell
B. Synergids
C. Antipodals
D. Nucellus

Answer: D

Reasoning Questions (Answer briefly)

1. Why is meiosis important in megaspore mother cell (MMC)?
Answer: It reduces chromosome number to haploid and produces genetic variation.

2. Why is only one megaspore functional?
Answer: The other three degenerate to provide nourishment to the functional megaspore.

3. Why are synergids important?
Answer:  They guide the pollen tube into the embryo sac using the filiform apparatus.

4. Why is the embryo sac called female gametophyte?
Answer:  Because it produces female gametes (egg cell) and is haploid.

5. Why is nucellus rich in food materials?
Answer: It nourishes the developing embryo sac.

Assertion–Reason Questions

1.
Assertion (A): The embryo sac is 8-nucleate and 7-celled.
Reason (R): Two nuclei remain free in the central cell.
Answer: Both A and R are true, and R is the correct explanation

2.
Assertion (A): Meiosis occurs in MMC.
Reason (R): It helps maintain chromosome number across generations.
Answer: Both A and R are true, and R is correct

3.
Assertion (A): Synergids help in fertilization.
Reason (R): They possess filiform apparatus.
Answer: Both A and R are true, and R is correct

4.
Assertion (A): All four megaspores develop into embryo sacs.
Reason (R): Megasporogenesis produces four megaspores.
Answer: A is false, R is true

5.
Assertion (A): The ovule is attached to placenta.
Reason (R): Placenta is present inside ovary.
Answer: Both A and R are true, but R is not the correct explanation

6.

Assertion (A): Embryo sac is called female gametophyte.
Reason (R): It produces egg cell and is haploid.

Answer: Both A and R are true, and R is correct

7.

Assertion (A): All megaspores are functional in angiosperms.
Reason (R): Meiosis produces four megaspores.

Answer: A is false, R is true

8.

Assertion (A): Synergids degenerate after fertilization.
Reason (R): They help in pollen tube entry.

Answer: Both A and R are true, but R is not the correct explanation

9.

Assertion (A): Embryo sac is 8-nucleate but 7-celled.
Reason (R): Two polar nuclei are present in one central cell.

Answer: Both A and R are true, and R is correct

10.

Assertion (A): Nucellus is haploid.
Reason (R): It surrounds the embryo sac.

Answer: A is false, R is true

Exam Tip (Very Important)

Remember these high-yield points:

• 7-celled, 8-nucleate embryo sac

• Monosporic development

• MMC → meiosis → 4 megaspores → 1 functional

• Synergids + filiform apparatus = pollen tube guidance

• Triple fusion → triploid endosperm

• 

Why Choose B.Sc, B.A & B.Com After Class 12: A Complete Career Guide

In today’s competitive world, many students blindly follow engineering or medical courses. But the reality is clear—B.Sc, B.A, and B.Com offer equal or even greater long-term success when chosen wisely.

These degrees are not “second options”—they are smart, flexible, and powerful career pathways.

🎓 1. Career Opportunities After Graduation

🔬 B.Sc (Science Stream)

🏛️ Government Jobs

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• Scientific Assistant
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• ₹2.2 LPA – ₹9 LPA for various government roles

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• Research Analyst
• Lab Technician
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• Average research roles around ₹3.4 LPA

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🏛️ Government Jobs

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• Banking Jobs (PO, Clerk)
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💰 Salary Range:

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• Civil services starting ~₹56,100/month + perks

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💰 Starting Salary:

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• MBA
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👉 Best for leadership roles, administration, and social impact careers

💼 B.Com (Commerce Stream)

🏛️ Government Jobs

• Bank PO / Clerk (IBPS, SBI)
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💰 Salary Range:

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🏢 Corporate / Private Jobs

• Accountant
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• Auditor
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💰 Starting Salary:

• ₹2.5 – ₹5 LPA
• ₹3 – ₹8 LPA depending on specialization

🎓 Higher Study Scope

• M.Com
• CA (Chartered Accountant)
• CS (Company Secretary)
• CMA / MBA

👉 Best for finance, business, and entrepreneurship careers

📊 2. Salary Comparison (After Graduation)

Degree	Government Jobs	Private Jobs
B.Sc	₹2.2 – ₹9 LPA	₹2.5 – ₹6 LPA
B.A	₹3 – ₹12 LPA	₹2 – ₹5 LPA
B.Com	₹3 – ₹15 LPA	₹2.5 – ₹8 LPA

👉 Salaries increase significantly with experience and higher studies.

🚀 3. Why These Degrees Can Be Better Than Engineering

• ✅ Less financial burden
• ✅ Wider career flexibility
• ✅ More chances in government jobs
• ✅ Strong base for UPSC & competitive exams
• ✅ Opportunities in emerging sectors

👉 Many engineers today prepare for UPSC, banking, and SSC, which are already open to B.A, B.Sc, and B.Com graduates.💡 4. Reality Check: What Truly Matters

No course guarantees success—not even engineering.

Success depends on:

• Skill development
• Hard work
• Smart career planning

👉 A dedicated B.Sc, B.A, or B.Com student can easily outperform others in career growth.

🌿 Final Message to Students

Do not follow the crowd. Follow your interest, strength, and long-term vision.

B.Sc, B.A, and B.Com are not ordinary degrees—they are gateways to:

• Government power (IAS, Banking, SSC)
• Corporate success
• Research & innovation
• Entrepreneurship

✨ Conclusion

👉 A degree does not decide your future—your determination does.

Choose wisely. Build skills. Stay focused.
And you will create a brighter career than any traditional path.

কেন্দ্ৰীয় আৰু ৰাজ্য চৰকাৰৰ বিভিন্ন চাকৰিৰ খবৰ- এপ্ৰিল মাহ ২০২৬

কেন্দ্ৰীয় আৰু ৰাজ্য চৰকাৰৰ বিভিন্ন বিভাগে বিজ্ঞাপন প্ৰকাশ কৰি নিম্নোলিখিত পদ পূৰণৰ বাবে আবেদন বিচৰা হৈছে। 

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What would be the ploidy of the cells of the tetrad?

The cells of a tetrad (formed during microsporogenesis in the anther) are haploid (n).

Explanation:

A diploid microspore mother cell (MMC, 2n) undergoes meiosis.

Meiosis consists of two successive divisions (Meiosis I and II).

This reduces the chromosome number by half.

As a result, four microspores are produced, arranged in a tetrad.

Final ploidy:

👉 Each of the four cells in the tetrad = haploid (n)

Why this is important:

These haploid microspores later develop into pollen grains (male gametophytes).

Haploidy ensures that during fertilization, fusion with the female gamete restores the diploid (2n) condition.

In short:

Tetrad cells are haploid (n) because they are produced by meiotic division of a diploid mother cell.

What is ploidy?

Ploidy refers to the number of complete sets of chromosomes present in a cell.

Basic idea:

Every organism has chromosomes that carry genetic information.

Ploidy tells you how many full sets of these chromosomes are present.

Common types of ploidy:

Haploid (n): One set of chromosomes

→ Example: gametes (sperm and egg cells)

Diploid (2n): Two sets of chromosomes (one from each parent)

→ Example: most body (somatic) cells in humans

Polyploid (3n, 4n, etc.): More than two sets of chromosomes

→ Common in many plants

Simple example:

In humans:

Haploid (n) = 23 chromosomes

Diploid (2n) = 46 chromosomes

In short:

👉 Ploidy = number of chromosome sets in a cell

How tapetal cells could become bi-nucleate?

Tapetal cells (of the anther) commonly become bi-nucleate through a process called endomitosis (or nuclear division without cytokinesis).

How it happens:

1. Normal mitotic division begins inside a tapetal cell.
2. The nucleus divides (karyokinesis occurs).
3. However, cytokinesis (cell division) does not take place.
4. As a result, two nuclei remain within a single cell, making it bi-nucleate.

Key mechanism:

• This process is often referred to as endomitosis or endomitotic division.
• In some cases, repeated cycles can even lead to multinucleate or polyploid tapetal cells.

Why this occurs:

Tapetal cells are highly metabolically active and play a crucial role in pollen development (nutrition, enzyme secretion, sporopollenin precursors).
Having two or more nuclei:

• Enhances metabolic capacity
• Supports rapid synthesis of materials needed for pollen wall formation

In short:

👉 Tapetal cells become bi-nucleate because nuclear division occurs without cell division, resulting in two nuclei within one cell.

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Paper Chromatography

 1. Introduction

Paper chromatography is a simple and widely used analytical technique for separating mixtures of substances based on their differential movement over a paper support. It is especially useful for separating amino acids, sugars, pigments, and small organic molecules.

2. Principle

Paper chromatography is mainly based on partition chromatography, where components distribute themselves between:

• Stationary phase: Water molecules adsorbed on cellulose fibers of the paper
• Mobile phase: Organic solvent moving through the paper

Explanation:

• Different substances travel at different rates depending on their solubility in the solvent and affinity for the paper.
• The separation is expressed using the Rf (retardation factor) value.

3. Types of Paper Chromatography

(A) Ascending Chromatography

• Solvent moves upward by capillary action
• Most commonly used method

(B) Descending Chromatography

• Solvent moves downward due to gravity
• Faster than ascending method

(C) Radial (Circular) Chromatography

• Solvent moves outward from the center
• Used for rapid qualitative analysis

(D) Two-Dimensional Chromatography

• Separation carried out in two directions using different solvents
• Useful for complex mixtures

4. Procedure

1. Preparation of Paper

   • Draw a baseline with pencil

2. Sample Application

   • Apply small spots of sample on the baseline

3. Development

   • Place paper in a chamber containing solvent
   • Solvent rises through capillary action

4. Separation

   • Components move at different rates

5. Detection

   • Spots visualized using:
     • UV light
     • Chemical reagents (e.g., ninhydrin for amino acids)

5. Applications

• Separation of amino acids and sugars
• Identification of plant pigments (chlorophyll, carotenoids)
• Detection of drugs and metabolites
• Food analysis (coloring agents, additives)
• Educational and research purposes

6. Merits (Advantages)

• Simple and inexpensive
• Requires minimal equipment
• Easy to perform and interpret
• Suitable for small sample quantities
• Multiple samples can be analyzed simultaneously

7. Demerits (Disadvantages)

• Low resolution compared to advanced techniques like HPLC
• Time-consuming for some separations
• Not suitable for large-scale analysis
• Limited sensitivity
• Environmental factors (humidity, temperature) may affect results

8. Conclusion

Paper chromatography is a fundamental and cost-effective technique for separating and identifying components of mixtures. Although it has lower precision compared to modern methods, it remains important for basic laboratory work, teaching, and preliminary analysis.

High Performance Liquid Chromatography (HPLC)

 1. Introduction

High Performance Liquid Chromatography (HPLC) is an advanced chromatographic technique used to separate, identify, and quantify components in a mixture. It operates under high pressure to push the liquid mobile phase through a tightly packed column, allowing efficient and rapid separation.

2. Principle

HPLC works on the principle of differential distribution (partitioning) of components between a stationary phase (solid adsorbent packed in a column) and a mobile phase (liquid solvent).

Where:

• = distribution coefficient
• = concentration of solute in stationary phase
• = concentration of solute in mobile phase

Explanation:

• Components with stronger interaction with the stationary phase move slowly.
• Components with weaker interaction move faster and elute earlier.
• This difference in retention time leads to separation.

3. Instrumentation (Main Components)

1. Solvent Reservoir – Contains mobile phase
2. Pump – Generates high pressure (up to ~400 bar or more)
3. Injector – Introduces sample into the system
4. Column – Packed with stationary phase (e.g., silica)
5. Detector – UV, fluorescence, or refractive index detector
6. Recorder/Data System – Produces chromatogram

4. Types of HPLC

• Normal Phase HPLC – Polar stationary phase, non-polar mobile phase
• Reverse Phase HPLC (RP-HPLC) – Non-polar stationary phase, polar mobile phase (most commonly used)
• Ion Exchange HPLC – Separation based on charge
• Size Exclusion HPLC – Separation based on molecular size

5. Applications

• Pharmaceutical analysis – Drug purity, quality control
• Biochemistry – Separation of proteins, peptides, amino acids
• Environmental analysis – Detection of pollutants, pesticides
• Food industry – Analysis of additives, vitamins, preservatives
• Clinical diagnostics – Blood and urine analysis

6. Merits (Advantages)

• High resolution and sensitivity
• Rapid and accurate analysis
• Can handle complex mixtures
• Quantitative and qualitative analysis possible
• Automation and reproducibility

7. Demerits (Disadvantages)

• Expensive instrumentation and maintenance
• Requires skilled operation
• High purity solvents required
• Limited sample capacity
• Possibility of column degradation over time

8. Conclusion

HPLC is a powerful analytical tool widely used in scientific research and industry. Its ability to provide precise, fast, and reliable separation makes it essential in modern chemistry, biology, and pharmaceutical sciences.

Ion Exchange Chromatography (IEC) –

1. Introduction

Ion exchange chromatography (IEC) is a separation technique based on the reversible exchange of ions between a charged stationary phase and ions in a solution (mobile phase). It is widely used to separate proteins, amino acids, nucleotides, and inorganic ions.

2. Principle

The technique works on electrostatic attraction between charged molecules and oppositely charged groups attached to the stationary phase.

• : Negatively charged resin
• : Initially bound ion
• : Ion from sample

Key idea:

• Positively charged ions (cations) bind to negatively charged resins.
• Negatively charged ions (anions) bind to positively charged resins.

3. Types of Ion Exchange Chromatography

(A) Cation Exchange Chromatography

• Stationary phase: Negatively charged (e.g., –COO⁻, –SO₃⁻ groups)
• Binds: Positively charged ions (cations like Na⁺, Ca²⁺, proteins with positive charge)

Examples of resins:

• Carboxymethyl cellulose (CM-cellulose)
• Sulfonated polystyrene resins

(B) Anion Exchange Chromatography

• Stationary phase: Positively charged (e.g., –NH₃⁺ groups)
• Binds: Negatively charged ions (anions like Cl⁻, PO₄³⁻, negatively charged proteins)

Examples of resins:

• DEAE-cellulose (Diethylaminoethyl cellulose)
• Q-sepharose

4. Components of the System

1. Stationary Phase (Ion Exchange Resin)

   • Insoluble matrix with charged functional groups
   • Can be organic polymers or cellulose-based materials

2. Mobile Phase (Eluent/Buffer)

   • Liquid that carries the sample
   • pH and ionic strength are crucial

3. Column

   • Glass or plastic tube packed with resin

5. Working Procedure

1. Column Equilibration

   • Column is equilibrated with a buffer of specific pH

2. Sample Application

   • Mixture of ions is introduced into the column

3. Binding

   • Oppositely charged ions bind to the resin

4. Washing

   • Unbound molecules are washed away

5. Elution

   • Bound ions are removed by:
     • Increasing salt concentration (ionic strength)
     • Changing pH

6. Detection

   • Collected fractions are analyzed

6. Factors Affecting Separation

• pH of buffer
  Determines charge on molecules (especially proteins)

• Ionic strength
  Higher salt concentration weakens electrostatic interactions

• Nature of resin
  Strong vs weak ion exchangers

• Flow rate
  Affects resolution and separation efficiency

7. Applications

• Separation and purification of proteins and enzymes
• Water softening (removal of Ca²⁺ and Mg²⁺ ions)
• Amino acid analysis
• Purification of nucleotides and nucleic acids
• Pharmaceutical and biochemical industries

8. Advantages

• High resolution and efficiency
• Selective separation based on charge
• Reusable resins
• Suitable for large-scale purification

9. Disadvantages

• Sensitive to pH and temperature changes
• Requires careful buffer preparation
• Some biomolecules may denature
• Cost of resins can be high

10. Summary

Ion exchange chromatography is a powerful and widely used analytical and preparative technique that separates molecules based on their charge. By adjusting pH and ionic strength, highly selective separations can be achieved, making it essential in biochemistry, environmental science, and industrial processes.

Paper Chromatography

Chlorophyll Separation

Preparation of Solvent 

✔ Recommended Solvent Mixture (Standard)

A widely used solvent mixture is:

Petroleum ether : Acetone = 9 : 1 (v/v)

👉 This is ideal for separating:

Carotene (orange)

Xanthophyll (yellow)

Chlorophyll a (blue-green)

Chlorophyll b (yellow-green)

🧪 Preparation of Solvent (Step-by-Step)

Materials Required:

Petroleum ether (boiling range 40–60°C)

Acetone (analytical grade)

Measuring cylinder

Stoppered bottle / reagent bottle

Procedure:

1. Take a clean, dry measuring cylinder.

2. Measure 90 ml of petroleum ether.

3. Add 10 ml of acetone slowly.

4. Transfer the mixture into a stoppered bottle.

5. Close tightly and mix gently by shaking.

6. Label the bottle:

👉 “Chromatography solvent: Petroleum ether : Acetone (9:1)”

⚠️ Important Precautions

Prepare solvent in a well-ventilated area (both solvents are volatile).

Keep away from open flames (highly flammable).

Use fresh solvent for better separation.

Ensure airtight container to prevent evaporation.

🔬 Alternative Solvent Systems (Optional)

You can also use:

1. Petroleum ether : Ethanol (9:1)

2. Hexane : Acetone (8:2)

3. Benzene : Acetone (9:1) (less preferred due to toxicity)

🎯 Role of Solvent

The solvent (mobile phase) carries pigments upward.

Separation occurs based on polarity differences:

Carotene (non-polar) → moves fastest

Chlorophyll b (more polar) → moves slowest

Identification of pigments 

To identify chlorophyll pigments after they move on the stationary phase (paper or TLC), you rely on a combination of colour, position (distance moved), and Rf value.

🌿 Typical Separation Pattern of Plant Pigments

After development, you will observe distinct coloured bands arranged from top to bottom:

Pigment Colour Relative Position Polarity Movement

Carotene Orange Top (farthest) Non-polar Fastest

Xanthophyll Yellow Below carotene Slightly polar Fast

Chlorophyll a Blue-green Middle Moderately polar Medium

Chlorophyll b Yellow-green Bottom (near origin) Most polar Slowest

📏 Identification Using Rf Value

The Rf (Retention factor) helps confirm pigment identity:

Rf = \frac{\text{Distance travelled by pigment}}{\text{Distance travelled by solvent front}}

✔ Steps to Calculate Rf:

1. Measure distance from origin to pigment band (cm).

2. Measure distance from origin to solvent front (cm).

3. Apply the formula.

📊 Typical Rf Values (approximate)

Pigment Rf Value (approx.)

Carotene 0.90 – 0.95

Xanthophyll 0.70 – 0.80

Chlorophyll a 0.50 – 0.60

Chlorophyll b 0.30 – 0.45

👉 Note: Values may vary depending on solvent system and conditions.

🔍 Key Principles Behind Identification

Polarity rule:

Non-polar pigments travel farther with non-polar solvent.

Polar pigments stick more to polar stationary phase (paper/silica).

Colour recognition:

Each pigment has a characteristic colour.

Order of movement:

👉 Top → Bottom:

Carotene → Xanthophyll → Chlorophyll a → Chlorophyll b

⚠️ Precautions for Accurate Identification

Mark the solvent front immediately after removal.

Do not disturb the bands while drying.

Use fresh extract for clear separation.

Avoid overloading the sample spot.