The following is the illustration of the sequence of ovarian events “a” to “i” in a human female:

(a) Identify the figure that illustrates corpus luteum and name the pituitary hormone that influences its formation.

(b) Specify the endocrine function of corpus luteum. How does it influence the uterus? Why is it essential?

(c) What is the difference between “d” and “e”?

(d) Draw a neat labelled sketch of Graafian follicle.

OR

(a) Why is fertilisation in an angiosperm referred to as double fertilisation? Mention the ploidy of the cells involved.

(b) Draw a neat labelled sketch of L.S. of an endospermous monocot seed.

a. Corpus luteum is depicted by “g”. Luteinizing hormone (LH) influences its formation.

b. Corpus luteum produces the hormone progesterone.
Progesterone causes proliferation of the endometrium.
It is essential for the implantation of the fertilized ovum and maintains the same during pregnancy

c. D is a developing tertiary follicle while e is a Graafian follicle.

d.

Figure 6. Structure of Graafian follicle.

OR

a. Fertilization in angiosperms is called double fertilization which is a complex fertilization mechanism specific to flowering plants. It is called so because it involves the process of syngamy and triple fusion in an embryo sac.

i. After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy. This results in the formation of a diploid cell, the zygote.

ii. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN). As this involves the fusion of three haploid nuclei it is termed triple fusion.

b.

Figure 7. L.S. of monocot seed (Maize).