Differentiate between microsporogenesis and megasporogenesis. Which type of cell division occurs during these events? Name the structures formed at the end of these two events.
Solution and Explanation
(a)
| Microsporogenesis | Megasporogenesis | |
| 1. | It is the process of the formation of microspore tetrads from a microspore mother cell through meiosis. | It is the process of the formation of the four megaspores from a megaspore mother cell in the region of the nucellus through meiosis |
| 2. | It occurs inside the pollen sac of the anther. | It occurs inside the ovule. |
(b) Both events (microsporogenesis and megasporogenesis) involve the process of meiosis or reduction division which results in the formation of haploid gametes from the microspore and megaspore mother cells.
(c) Microsporogenesis results in the formation of haploid microspores from a diploid microspore mother cell. On the other hand, megasporogenesis results in the formation of haploid megaspores from a diploid megaspore mother cell.
Top Questions on sexual reproduction in flowering plants
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.- CBSE CLASS XII - 2025
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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.
- CBSE CLASS XII - 2025
- Biology
- sexual reproduction in flowering plants
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.
- CBSE CLASS XII - 2025
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- What are the significances of double fertilization?
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- How many meiotic divisions are required for the formation of 300 seeds in angiosperm?
- Maharashtra Class XII - 2025
- Biology
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Concepts Used:
Pre-fertilization events - Monoecious Plant
Fertilization in plants may be a process during which they undergo amphimixis in consequence of pollination and germination. During a physicochemical process, the male gametes (known as pollen) infusion with the feminine gametes (known as ovum) forms diploid zygote after carpal pollinates. The whole process happens in a zygote which later germinates into a seed. During the method, what happens is male gametes are transferred into female reproductive organs through pollinators (butterflies, birds, honey bees, bats, and flower beetles). This leads to an embryo being formed during a seed. Flowers are the reproductive organs of angiosperms and reproduce in a completely different method.
Read More: Flower Structure
The two important pre-fertilization procedures are gametogenesis and gamete transfer. The female and male reproductive forms in flowers are the androecium and the gynoecium which distinguishes and goes through development.
"Mono" means single so a monoecious plant is one that bears both male and female sex organs on same plant. The monoecious plant can produce bisexual flowers or unisexual flowers. A dioecious plant is one that bears both male and female sex organs on different plants.
Read Further: Sexual Reproduction in Flowering Plants