✓ Board-verified
Biology · 2025 · 5 marks
CBSE 2025 · Region 2 · Set 1 · Q31
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…
Student to attempt either option (A) or (B).
(i)
Describe the process of megasporogenesis in an angiosperm.
(ii)
Draw a diagram of a mature embryo sac of an angiosperm. Label its any four parts.
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.
Marking-scheme solution
(i)
( Meiosis)
Megaspore mother cell
Tetrad
(2n) (n)
$\displaystyle 3$ Mitosis without cell wall formation / Degeneration of $\displaystyle 3$ cells
Free Nuclear division (one functional megaspore left)
(n)
(Cell wall formation)
$\displaystyle 8$ nuclear stage Embryo sac ($\displaystyle 7$ celled $\displaystyle 8$ nucleated stage)
(ii)
(i)
Menstrual phase → proliferative / follicular phase → ovulatory
phase → luteal / secretory phase.
(ii)
$\displaystyle 3$ – $\displaystyle 5$ days.
(iii)
Estrogen reaches its peak during proliferative phase just before ovulation, because it is secreted by the growing follicles.
Progesterone reaches its peak during luteal phase or secretory phase, it is because progesterone is secreted by corpus luteum.
(iv)
LH surge induces rupture of Graafian follicle / the release of ovum /ovulation.
All Human Reproduction questions2025 question paperNCERT solutions: Human ReproductionPractice Human Reproduction →
More from Human Reproduction
- Colostrum secreted by the mother's mammary glands in a human female during the initial days of lactation is rich in antibody:2025
- Which of the following options correctly matches the name of the hormone to its site of production in the human body?2023
- (i) Describe the events of spermatogenesis with the help of a A schematic diagram. (ii) Explain the role of hormones in spermatogenesis. OR (i) Show…2024
- Given below are few statements with reference to the human male reproductive system. (i) Paired seminal vesicles, prostate gland and bulbourethral…2025
- Given below are a few statements with reference to the human sperm. (i) Sperm head contains a large nucleus and a lot of cytoplasm. (ii) Mitochondria…2025
- Which of the following hormones is not secreted by the human placenta?2023
- Explain the neuroendocrine mechanism involved in the process of parturition in a human female leading to the expulsion of the baby out of the uterus…2025
- Given below are structural details of a human mammary gland: 1 (i) The glandular tissue in the breast has 15-20 clusters of cells called alveoli.…2023
CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.