Question

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.

Hint:

Megasporogenesis produces the megaspore that develops into the embryo sac, while the menstrual cycle’s hormonal peaks, like the LH surge, are key for ovulation and pregnancy preparation.

Answer 1

(A):
Step 1: For (i), megasporogenesis in an angiosperm is the process of forming megaspores in the ovule. It begins with a diploid megaspore mother cell (MMC) in the nucellus of the ovule. The MMC undergoes meiosis to produce four haploid megaspores. Typically, three megaspores degenerate, and one functional megaspore survives, which then develops into the embryo sac through megagametogenesis. 
Step 2: For (ii), a mature embryo sac (female gametophyte) of an angiosperm is a 7-celled, 8-nucleate structure. It consists of: (1) the egg apparatus at the micropylar end with one egg cell and two synergids, (2) three antipodal cells at the chalazal end, (3) a large central cell with two polar nuclei, and (4) the overall sac surrounded by the integuments of the ovule. The diagram would show an oval structure with these labeled parts: egg cell, synergids, central cell, and antipodal cells. 
OR 
(B): 
Step 3: For (i), the four phases of the menstrual cycle in sequence are: (1) menstrual phase, (2) follicular phase, (3) ovulatory phase, and (4) luteal phase. 
Step 4: For (ii), the menstrual phase typically lasts 3 to 5 days, during which the uterine lining sheds if no pregnancy occurs. 
Step 5: For (iii), estrogen peaks during the late follicular phase (around day 12–14) to stimulate the growth of the uterine lining and trigger the LH surge, while progesterone peaks during the luteal phase (around day 21) to maintain the endometrium for potential pregnancy. 
Step 6: For (iv), the LH surge, occurring around day 14, triggers ovulation by causing the mature follicle to rupture and release the egg, a critical step for reproduction. 
Thus, (A) describes megasporogenesis and the embryo sac structure, while (B) details the menstrual cycle phases, their duration, hormone peaks, and the role of the LH surge.