Class 12 Biology – Sexual Reproduction in Flowering Plants MCQs with Answers
In Class 12 Biology, many students understand the story of reproduction in flowering plants but lose marks in MCQs due to small details like ploidy, seed parts, and the correct sequence of events. This page helps you revise the chapter through exam-style questions with answers and short explanations. It is useful for CBSE board preparation and for practising NCERT-based concepts that also appear in NEET-level objective questions. Try to solve without looking at the answer first, then check the explanation.
Core Content (MCQs)
Question 1
What is the ploidy of the primary endosperm nucleus (PEN) formed after fertilisation?
A. Diploid (2n) B. Triploid (3n) C. Haploid (n) D. Tetraploid (4n)
Answer: B
Explanation: PEN forms when one male gamete (n) fuses with two polar nuclei (n + n), giving 3n.
Why the other options are wrong (quick check):
- A/C/D: They do not match the n + n + n fusion that forms the endosperm nucleus.
Question 2
Assertion (A): The micropyle remains as a small pore in the seed coat. Reason (R): The micropyle helps water and oxygen enter the seed during germination.
A. Both A and R are true and R is the correct explanation of A. B. Both A and R are true but R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
Answer: A
Explanation: The micropyle is a tiny opening left in the seed coat, and it helps in water uptake and gas exchange during germination.
Why the other options are wrong (quick check):
- B: R directly explains the function of the micropyle.
- C/D: Both A and R are correct.
Question 3
What is the ploidy level of cells in a microspore tetrad formed during microsporogenesis?
A. Diploid (2n) B. Haploid (n) C. Triploid (3n) D. Tetraploid (4n)
Answer: B
Explanation: A diploid pollen mother cell undergoes meiosis and forms four haploid microspores arranged as a tetrad.
Why the other options are wrong (quick check):
- A: 2n is the pollen mother cell before meiosis.
- C/D: These ploidies do not apply to microspores.
Revision Tip: If the word “meiosis” appears, expect the ploidy to reduce from 2n to n.
Question 4
Which seed is non-albuminous (without residual endosperm at maturity)?
A. Wheat B. Castor C. Pea D. Maize
Answer: C
Explanation: In pea, endosperm is consumed during embryo development, so the mature seed is non-albuminous.
Why the other options are wrong (quick check):
- A/D: Cereals like wheat and maize are albuminous.
- B: Castor is a classic example of albuminous seed.
Question 5
What is the correct sequence of events during microsporogenesis?
A. Sporogenous tissue → microspore mother cell → meiosis → microspore tetrad → pollen grain B. Microspore mother cell → sporogenous tissue → meiosis → pollen grain → microspore tetrad C. Sporogenous tissue → meiosis → microspore mother cell → microspore tetrad → pollen grain D. Microspore tetrad → sporogenous tissue → meiosis → microspore mother cell → pollen grain
Answer: A
Explanation: Sporogenous tissue gives rise to microspore mother cells, which undergo meiosis to form tetrads that later develop into pollen grains.
Why the other options are wrong (quick check):
- B/C/D: They place meiosis or stages in the wrong order.
Question 6
Assertion (A): Microspores develop into pollen grains after dissociation from the tetrad. Reason (R): Microspores remain attached as tetrads throughout pollen development.
A. Both A and R are true and R is the correct explanation of A. B. Both A and R are true but R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
Answer: C
Explanation: Microspores separate from the tetrad; each microspore matures into a pollen grain. They do not remain attached as tetrads.
Why the other options are wrong (quick check):
- A/B: R is false.
- D: A is true.
Revision Tip: Remember: tetrad is a temporary stage. Final pollen grains are separate units.
Question 7
Assertion (A): The mature embryo sac in angiosperms is 7-celled and 8-nucleate. Reason (R): It has two synergids, one egg cell, three antipodals, and a central cell with two polar nuclei.
A. Both A and R are true and R is the correct explanation of A. B. Both A and R are true but R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
Answer: A
Explanation: The central cell counts as one cell but contains two nuclei, giving 8 nuclei in total.
Why the other options are wrong (quick check):
- B: R explains A.
- C/D: Both statements are correct.
Question 8
Which statement about anther structure is correct?
A. An anther is single-lobed with two microsporangia. B. A typical anther is bilobed and dithecous, with two theca in each lobe. C. A microsporangium is surrounded by three wall layers. D. The filament is the terminal part that bears the anther.
Answer: B
Explanation: A typical angiosperm anther is bilobed and has four microsporangia (two in each lobe), so it is dithecous.
Why the other options are wrong (quick check):
- A: Typical anther is bilobed.
- C: There are four wall layers in the microsporangium.
- D: Anther is terminal; filament supports it.
Question 9
Which statement is true regarding hybrid seeds and apomixis?
A. Apomixis causes segregation of hybrid characters. B. Hybrid seeds produced by apomixis maintain hybrid characters without segregation. C. Hybrid seeds need not be produced every year if apomixis is absent. D. Apomixis increases the cost of hybrid seed production.
Answer: B
Explanation: Apomixis produces seeds without fertilisation, so the offspring are like the parent and hybrid characters are preserved.
Why the other options are wrong (quick check):
- A: Segregation is avoided in apomixis.
- C: Without apomixis, traits may segregate.
- D: Apomixis can reduce repeated seed production needs.
Revision Tip: “Double fertilisation = two fusions.” One gives zygote, the other gives endosperm.
Question 10
Assertion (A): Double fertilisation is unique to flowering plants. Reason (R): It involves fusion of two male gametes with two different nuclei in the embryo sac.
A. Both A and R are true and R is the correct explanation of A. B. Both A and R are true but R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
Answer: A
Explanation: One male gamete fuses with the egg to form the zygote, and the other fuses with polar nuclei to form the endosperm.
Why the other options are wrong (quick check):
- B: R explains why the process is called double fertilisation.
- C/D: Both A and R are correct.
You may also practice: Class 12 Biology – Sexual Reproduction in Flowering Plants MCQs (Mixed Practice)
Continue practicing to strengthen your understanding and build consistency.