List of top Biology Questions on sexual reproduction in flowering plants asked in CBSE CLASS XII

Answer the following questions:

[(i)] Explain the structure of a mature embryo sac of a typical flowering plant.

[(ii)] How is triple fusion achieved in these plants?

OR

[(i)] Describe the changes in the ovary and the uterus as induced by the changes in the level of pituitary and ovarian hormones during menstrual cycle in a human female.

Flowering plants with hermaphrodite flowers have developed many reproductive strategies to ensure cross-pollination. Study the given outbreeding devices adopted by certain flowering plants and answer the questions that follow.

Note : All plants belong to the same species. No pollen tube growth/inhibition of pollen germination on stigma. Pollen germination on stigma.

  • [(a)] Name and define the outbreeding device described in the above table.
  • [(b)] Explain what would have been the disadvantage to the plant in the absence of the given strategy.
Select the statements that are true for the seed of angiosperm from the given options:
(i) Non-albuminous seeds have no residual endosperm.
(ii) Residual, persistent nucellus in wheat is known as perisperm.
(iii) Integuments of ovules harden as tough protective seed coat.
(iv) Metabolic activity of the embryo slows down in dormancy.
Choose the correct option:
Unisexuality of flowers prevents which process?

Student to attempt either option (A) or (B).
(A) 
(i) Describe the process of megasporogenesis in an angiosperm. 
(ii) Draw a diagram of a mature embryo sac of the angiosperm. Label its any four parts. 
OR
(B) The reproductive cycle in the female primates is called menstrual cycle. The first menstruation begins at puberty. 
Answer the following questions: 
(i) Name the four phases of menstrual cycle in a proper sequence. 
(ii) How long does the menstrual phase last in a menstrual cycle? 
(iii) When and why hormones estrogen and progesterone reach their peak levels respectively, in the menstrual cycle? 
(iv) Give the significance of LH surge.

Student to attempt either option (A) or (B):
(A) 
(i) Write two crucial changes, the seed undergoes while reaching maturity that enable them to be in a viable state until the onset of favourable conditions. 
(ii) Name the oldest viable seed excavated from Arctic Tundra as per the records. 
OR (B) 
(i) Pea flower produced seed sets. Give reason. 
(ii) In case of Polyembryony, an embryo ‘P’ develops from a synergid and the embryo ‘Q’ develops from the nucellus. State the ploidy of embryo ‘P’ and ‘Q’.

(a) A bilobed dithecous anther has 200 microspore mother cells per microsporangium. How many male gametophytes can be produced by this anther?
(b) Write the composition of intine and exine layers of a pollen grain.

Given below is a diagram of T.S. of a monocot seed with parts I, II & III labelled :

Choose the option where parts I, II and III are identified correctly.

Select the statements that are true for outbreeding devices in the flowering plants.
    [(i)]
  • They discourage cross-pollination and ensure self-pollination.
  • They are advantageous as they lead to inbreeding depression.
  • Self-incompatibility prevents self-pollen from fertilising the ovules.
  • To prevent self-pollination in some species pollen release and stigma receptivity are not synchronised.
Choose the correct answer:
Select the statements that are true for a typical megasporangium of flowering plants:
(i) It is attached to the placenta by hilum.
(ii) It has a chalaza end that represents the basal part of the ovule.
(iii) It has nucellus enclosed by integuments.
(iv) Its micropylar end is known as chalaza.
Choose the correct answer:

Given below is a flower with its characteristic features specialised for the most common type of abiotic pollination.

Answer the following questions based on the above diagram:
(a) Name the mode of abiotic pollination that will be adopted by the given plant species in the above picture.
(b) State the need of exposed large feathery stigmas for the flower.
(c) What will be the two important adaptations in the pollen grains of the flowers pollinated by the above mode of pollination?
(d)What could be the probable reason for the petals being small and non-green?

Assertion (A): Perisperm is a diploid tissue.
Reason (R): Perisperm is the remains of nucellus which surrounds the embryo in certain seeds.
Select the statements that are true for pollination mechanism in flowering plants from the given options:

(a) (i) Explain the structure of a typical monocotyledonous embryo of a flowering plant.
(ii) How are multiple embryos formed in a citrus fruit? What is the mechanism known as?

OR

(b) (i) Name and explain the structural organization of the male sex accessory ducts in the human male reproductive system.
(ii) Describe the role of gonadotropin FSH (Follicle-Stimulating Hormone) in the regulation of spermatogenesis.

How many pollen grains and ovules are likely to be formed in the anther and ovary of an angiosperm bearing 50 microspore mother cells and 50 megaspore mother cells respectively?
Explain the structure of a mature embryo sac of a typical flowering plant.
How is triple fusion achieved in these plants ?
Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with the help of any two examples.
Assertion (A): In some species of asteraceae and grasses, seeds are formed without fertilization.
Reason (R): Formation of fruit without fertilization is called parthenocarpy.
Select the statements that are true for the embryo of the flowering plants from the given options:
1. The zygote forms a proembryo and subsequently heart-shaped, globular and mature embryo.
2. Most zygotes divide to form embryo only after a certain amount of endosperm is formed.
3. The embryo develops at the micropylar end of the embryo sac.
4. A typical dicotyledonous embryo consists of an embryonal axis and a scutellum.
Choose the correct option from the following:
Explain the development of male gametophyte in an angiosperm.
Draw a labelled diagram of a three-celled male gametophyte.
Mention two strategies evolved to prevent self-pollination in flowers.
If one can induce parthenocarpy through the application of growth substances which fruits would you select to induce parthenocarpy and why?
Why do you think the zygote is dormant for sometime in a fertilized ovule?