Chapter 2: Sexual Reproduction in Flowering Plants – Case-Based / Source-Based Questions with Answers
CBSE Class 12 Biology – Case-Based 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 Focus: CBSE Class 12 Board Examinations (Competency-Based / Case-Based Questions)
CBSE Class 12 Biology Chapter 2 Case-Based Questions – Sexual Reproduction in Flowering Plants (NCERT)
Section A: Flower as a Reproductive Organ
Case 1
A student observes a flower with sepals, petals, stamens, and carpels arranged in whorls.
Q1. Why is this flower called a complete flower?
Ans: It is called complete because all four floral whorls—calyx, corolla, androecium, and gynoecium—are present.
Case 2
A plant bears flowers containing only stamens.
Q2. What type of flower is this?
Ans: It is a unisexual male flower because it contains only androecium.
Case 3
Brightly coloured petals are observed in insect-pollinated flowers.
Q3. State the role of petals in reproduction.
Ans: Petals attract insects, thereby facilitating pollination and successful fertilisation.
Section B: Structure of Stamen and Carpel
Case 4
A transverse section of an anther shows four pollen sacs.
Q4. Name the structure present inside pollen sacs.
Ans: Pollen sacs contain microspore mother cells that form pollen grains.
Case 5
The innermost anther wall layer degenerates after pollen formation.
Q5. Identify this layer and its function.
Ans: The tapetum nourishes developing pollen grains and later degenerates.
Case 6
Ovules are attached to a cushion-like tissue inside the ovary.
Q6. Name this tissue.
Ans: The tissue is called placenta.
Section C: Microsporogenesis and Pollen Grain
Case 7
A diploid cell in the anther undergoes meiosis.
Q7. Name the process and product formed.
Ans: Microsporogenesis; four haploid microspores are formed.
Case 8
A pollen grain survives extreme heat and chemicals.
Q8. Which component provides this resistance?
Ans: Sporopollenin present in the exine provides resistance.
Case 9
A pollen grain contains two cells at maturity.
Q9. Name these cells.
Ans: Vegetative cell and generative cell.
Section D: Megasporogenesis and Embryo Sac
Case 10
Four megaspores are formed inside an ovule, but only one survives.
Q10. What happens to the remaining megaspores?
Ans: Three megaspores degenerate, leaving one functional megaspore.
Case 11
A seven-celled structure is observed inside the ovule.
Q11. Identify this structure.
Ans: It is the embryo sac, the female gametophyte.
Case 12
Two synergids are seen near the micropyle.
Q12. Mention one function of synergids.
Ans: They guide the pollen tube towards the egg cell.
Section E: Pollination
Case 13
Pollen transfer occurs within the same flower.
Q13. Name this type of pollination.
Ans: Autogamy.
Case 14
Pollen from one flower reaches another flower of the same plant.
Q14. Identify the pollination type.
Ans: Geitonogamy.
Case 15
Pollination occurs between flowers of different plants.
Q15. Why is this type important?
Ans: Xenogamy promotes genetic variation.
Case 16
Flowers are small, light, and produce large amounts of pollen.
Q16. Which pollinating agent is involved?
Ans: Wind (anemophily).
Section F: Double Fertilisation
Case 17
Two male gametes are released into the embryo sac.
Q17. What is this phenomenon called?
Ans: Double fertilisation.
Case 18
One male gamete fuses with the egg cell.
Q18. Name the process and product.
Ans: Syngamy; a diploid zygote is formed.
Case 19
The second male gamete fuses with polar nuclei.
Q19. What is formed as a result?
Ans: Triploid primary endosperm nucleus.
Section G: Post-Fertilisation Changes
Case 20
A nutritive tissue develops before the embryo matures.
Q20. Identify this tissue.
Ans: Endosperm.
Case 21
Repeated free nuclear divisions occur in endosperm.
Q21. Name this type of endosperm development.
Ans: Nuclear endosperm development.
Case 22
A fertilised ovule develops a protective covering.
Q22. What does it form?
Ans: Seed with a seed coat derived from integuments.
Section H: Embryo, Seed, and Fruit Formation
Case 23
The zygote divides to form an embryo with two cotyledons.
Q23. Identify the type of embryo.
Ans: Dicot embryo.
Case 24
The ovary wall becomes fleshy after fertilisation.
Q24. What does it form?
Ans: Fruit.
Case 25
Some fruits develop from ovary and thalamus.
Q25. What type of fruit is this?
Ans: False fruit.
Section I: Apomixis and Polyembryony
Case 26
Seeds are formed without fertilisation in some plants.
Q26. Name this phenomenon.
Ans: Apomixis.
Case 27
Multiple embryos develop within a single seed.
Q27. What is this condition called?
Ans: Polyembryony.
Case 28
In citrus, embryos arise from nucellus.
Q28. Identify the type of polyembryony.
Ans: Adventive polyembryony.
Section J: Integrated Concept-Based Cases
Case 29
A flower shows dichogamy.
Q29. State its significance.
Ans: It prevents self-pollination and promotes cross-pollination.
Case 30
A sexually reproducing plant population adapts better to environment.
Q30. State one reason for this advantage.
Ans: Genetic variation produced during sexual reproduction enhances adaptability.
CBSE Board Exam Note
These 30 Case-Based Questions with Answers are strictly NCERT-aligned, framed as per the CBSE Class 12 competency-based assessment pattern, and ideal for board exam preparation and concept application.