Chapter 2: Sexual Reproduction in Flowering Plants – Short Answer Type Questions

CBSE Class 12 Biology – Short Answer Type Questions with Answers

Unit I: Reproduction | Chapter 2: Sexual Reproduction in Flowering Plants (NCERT Based)

Course & Examination Details

• Course: CBSE Class 12 Biology
• Prescribed By: Central Board of Secondary Education
• Syllabus Reference: NCERT
• Unit: Unit I – Reproduction
• Chapter: Chapter 2 – Sexual Reproduction in Flowering Plants
• Exam Relevance: CBSE Class 12 Board Examinations (2–3 Mark Questions)

CBSE Class 12 Biology Chapter 2 Short Answer Questions – Sexual Reproduction in Flowering Plants (NCERT)

Section A: Flower as a Reproductive Organ

Q1. Explain why a flower is considered a reproductive organ.

Ans:
A flower is considered the reproductive organ of angiosperms because it bears the male (androecium) and female (gynoecium) reproductive structures. These organs produce gametes, facilitate pollination and fertilisation, and finally lead to seed and fruit formation, ensuring sexual reproduction.

Q2. Describe the arrangement of floral whorls in a typical flower.

Ans:
A typical flower has four concentric whorls arranged on the thalamus. From outer to inner, these are calyx, corolla, androecium, and gynoecium. Each whorl performs a specific function, collectively ensuring protection, attraction of pollinators, and sexual reproduction.

Q3. Differentiate between bisexual and unisexual flowers.

Ans:
Bisexual flowers contain both androecium and gynoecium in the same flower, enabling production of male and female gametes together. Unisexual flowers contain either androecium or gynoecium, as seen in papaya, requiring cross-pollination for fertilisation.

Q4. State two functions of petals in a flower.

Ans:
Petals attract pollinators through bright colours, fragrance, and nectar secretion. They also help guide pollinators towards reproductive organs, thereby increasing the chances of successful pollination.

Q5. What is the significance of thalamus in a flower?

Ans:
The thalamus is the swollen terminal part of the floral axis that bears all floral whorls. It provides structural support and proper arrangement of floral organs for effective reproduction.

Section B: Structure of Stamen and Carpel

Q6. Describe the structure of a stamen.

Ans:
A stamen consists of a long filament and a terminal anther. The anther is bilobed, with each lobe containing two microsporangia. These microsporangia produce pollen grains that carry male gametes.

Q7. Explain the structure of a typical anther.

Ans:
A typical anther is bilobed with four microsporangia. Its wall has four layers: epidermis, endothecium, middle layers, and tapetum. The tapetum provides nourishment to developing pollen grains.

Q8. What is the role of tapetum?

Ans:
Tapetum is the innermost layer of the anther wall. It supplies nutrients, enzymes, and sporopollenin precursors required for pollen grain development and maturation.

Q9. Describe the structure of a carpel.

Ans:
A carpel consists of stigma, style, and ovary. The stigma receives pollen grains, the style connects stigma to ovary, and the ovary contains ovules that develop into seeds after fertilisation.

Q10. What is placentation?

Ans:
Placentation refers to the arrangement of ovules within the ovary. It determines the number and position of ovules, influencing seed formation.

Section C: Microsporogenesis and Pollen Grain

Q11. Explain microsporogenesis.

Ans:
Microsporogenesis is the process by which diploid microspore mother cells undergo meiosis to form four haploid microspores. These microspores later develop into pollen grains.

Q12. Describe the structure of a pollen grain.

Ans:
A pollen grain has a double-layered wall: an outer exine made of sporopollenin and an inner intine. It contains a vegetative cell and a generative cell responsible for male gamete formation.

Q13. Why are pollen grains highly resistant?

Ans:
Pollen grains are resistant due to sporopollenin in the exine, which protects them from heat, chemicals, and enzymatic degradation.

Q14. What is the function of the generative cell?

Ans:
The generative cell divides mitotically to form two male gametes that participate in double fertilisation.

Q15. What is pollen viability?

Ans:
Pollen viability refers to the ability of pollen grains to remain functional and capable of fertilisation for a certain period after release.

Section D: Megasporogenesis and Embryo Sac

Q16. Explain megasporogenesis.

Ans:
Megasporogenesis is the formation of haploid megaspores from a diploid megaspore mother cell through meiosis inside the ovule.

Q17. Describe the development of embryo sac.

Ans:
The functional megaspore undergoes mitotic divisions to form a seven-celled, eight-nucleate embryo sac, representing the female gametophyte.

Q18. What is the egg apparatus?

Ans:
The egg apparatus consists of one egg cell and two synergids located at the micropylar end of the embryo sac, aiding fertilisation.

Q19. State the function of synergids.

Ans:
Synergids secrete chemical attractants that guide the pollen tube towards the egg cell for fertilisation.

Q20. What is the role of antipodal cells?

Ans:
Antipodal cells are believed to provide nourishment and support during embryo sac development.

Section E: Pollination

Q21. Define pollination and its importance.

Ans:
Pollination is the transfer of pollen grains from anther to stigma. It is essential for bringing male gametes close to female gametes, enabling fertilisation.

Q22. Differentiate between autogamy and xenogamy.

Ans:
Autogamy involves pollination within the same flower, while xenogamy involves transfer of pollen between different plants of the same species, promoting variation.

Q23. Explain geitonogamy.

Ans:
Geitonogamy occurs when pollen is transferred between different flowers of the same plant. Though genetically similar, it requires pollinating agents.

Q24. What are abiotic agents of pollination?

Ans:
Abiotic agents include wind and water, which transfer pollen without involvement of living organisms.

Q25. Mention two outbreeding devices.

Ans:
Dichogamy and self-incompatibility prevent self-pollination and promote cross-pollination.

Section F: Double Fertilisation

Q26. Explain double fertilisation.

Ans:
Double fertilisation involves syngamy forming zygote and triple fusion forming primary endosperm nucleus within the same embryo sac.

Q27. Why is double fertilisation important?

Ans:
It ensures simultaneous development of embryo and nutritive endosperm, preventing wastage of resources.

Q28. What is triple fusion?

Ans:
Triple fusion is the fusion of one male gamete with two polar nuclei, forming a triploid endosperm nucleus.

Q29. Define syngamy.

Ans:
Syngamy is the fusion of one male gamete with the egg cell, forming a diploid zygote.

Q30. Why is double fertilisation unique to angiosperms?

Ans:
Only angiosperms show fertilisation of two different cells by two male gametes within the embryo sac.

Section G: Post-Fertilisation Changes

Q31. Describe endosperm development.

Ans:
Endosperm develops from the primary endosperm nucleus and provides nutrition to the developing embryo.

Q32. What are the types of endosperm development?

Ans:
The three types are nuclear, cellular, and helobial endosperm development.

Q33. Explain embryo development in dicots.

Ans:
The dicot embryo consists of two cotyledons, plumule, and radicle formed through organised cell divisions of the zygote.

Q34. What changes occur in ovule after fertilisation?

Ans:
The ovule develops into a seed, and integuments form the seed coat.

Q35. How does ovary transform after fertilisation?

Ans:
The ovary enlarges and matures into a fruit enclosing seeds.

Section H: Apomixis and Polyembryony

Q36. What is apomixis?

Ans:
Apomixis is seed formation without fertilisation, producing genetically identical offspring.

Q37. State one agricultural advantage of apomixis.

Ans:
It preserves hybrid vigor and desirable traits across generations.

Q38. Define polyembryony.

Ans:
Polyembryony is the occurrence of more than one embryo in a single seed.

Q39. Name a plant showing polyembryony.

Ans:
Citrus commonly exhibits polyembryony.

Q40. From where do adventive embryos arise?

Ans:
Adventive embryos arise from nucellus or integuments instead of zygote.

Section I: Conceptual Understanding

Q41. Why is pollination essential before fertilisation?

Ans:
Pollination transfers pollen to stigma, allowing pollen tube growth and fertilisation.

Q42. What is the role of pollen tube?

Ans:
The pollen tube transports male gametes to the embryo sac.

Q43. Why are seeds advantageous to plants?

Ans:
Seeds protect embryos and aid dispersal and survival.

Q44. Why is sexual reproduction important in plants?

Ans:
It generates genetic variation, ensuring adaptability and evolution.

Q45. What is the function of seed coat?

Ans:
The seed coat protects the embryo from mechanical damage and desiccation.

Section J: Higher-Order Understanding

Q46. Why is xenogamy preferred evolutionarily?

Ans:
Xenogamy introduces maximum genetic variation, enhancing adaptability.

Q47. How do flowers ensure cross-pollination?

Ans:
Through outbreeding devices like dichogamy and herkogamy.

Q48. Why is endosperm necessary?

Ans:
It provides nutrition to the developing embryo.

Q49. How does fruit formation aid seed dispersal?

Ans:
Fruits attract animals or develop structures aiding dispersal.

Q50. Summarise the significance of sexual reproduction in flowering plants.

Ans:
It ensures seed formation, variation, adaptability, and species continuity.

CBSE Board Exam Note

These Short Answer Type Questions (60–80 words each) are strictly NCERT-based, aligned with CBSE Class 12 Biology board examination standards, and ideal for 2–3 mark answers and concept clarity.