CBSE Class 12 Science Biology · Ch 1: Sexual Reproduction in Flowering Plants

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Difficulty: 3 easy · 8 medium · 19 hard

Sample questions with answers

The first 5 questions of this free test.

1. Q1. Flowering plants have developed several devices to prevent self-pollination and encourage cross-pollination. Which one of the following is the odd one out?

   • A. Pollen release and stigma receptivity at different times
   • B. Self-incompatibility
   • C. Cleistogamy
   • D. Anther and stigma placed at different positions
   Solution

   Cleistogamy (flowers that never open) guarantees self-pollination/autogamy, whereas the other three are contrivances that discourage self-pollination.

2. Q2. Consider the following statements about pollen grains: (i) Sporopollenin of the exine can be easily degraded by high temperature and strong acids or alkalis. (ii) Germ pores are the regions where the exine is absent or thin. (iii) In most angiosperms pollen is shed at the 2-celled stage. (iv) Pollen grains can be stored for years in liquid nitrogen for use in pollen banks. Which statements are correct?

   • A. (i) and (iv) only
   • B. (i), (ii), (iii) and (iv)
   • C. (ii), (iii) and (iv)
   • D. (i), (ii) and (iii)
   Solution

   Sporopollenin is one of the most resistant materials and is NOT degraded by heat or acids/alkalis, so (i) is wrong while (ii), (iii) and (iv) are correct.

3. Q3. Assertion (A): Fertilization in angiosperms is termed double fertilization. Reason (R): One male gamete fuses with the egg forming the zygote while the other male gamete fuses with the two polar nuclei forming the primary endosperm nucleus. Select the correct option.

   • A. Both A and R are true and R is the correct explanation of A
   • B. A is true but R is false
   • C. A is false but R is true
   • D. Both A and R are true but R is not the correct explanation of A
   Solution

   Both syngamy and triple fusion occur in each embryo sac, so two fusion events (double fertilization) take place, and the reason correctly explains the assertion.

4. Q4. Match Column I with the correct ploidy in Column II and choose the right option. Column I: (A) Antipodal cells (B) Primary endosperm nucleus (C) Nucellus (D) Egg cell Column II: (i) $3n$ (ii) $n$ (iii) $2n$

   • A. A-ii, B-iii, C-i, D-ii
   • B. A-iii, B-i, C-ii, D-ii
   • C. A-i, B-ii, C-iii, D-ii
   • D. A-ii, B-i, C-iii, D-ii
   Solution

   Antipodals and egg are haploid $n$, the nucellus is diploid $2n$ sporophytic tissue, and the primary endosperm nucleus is triploid $3n$ because two polar nuclei fuse with one male gamete.

5. Q5. After meiosis in the ovule, three megaspores degenerate and the single functional megaspore forms the embryo sac. The number of successive free-nuclear mitotic divisions needed to produce the 8 nuclei of this embryo sac is:

   • A. 3
   • B. 7
   • C. 4
   • D. 8
   Solution

   The functional megaspore nucleus divides mitotically three times (1→2→4→8), producing 8 nuclei by free-nuclear division.

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