Question

(a) (i) Explain how does double fertilisation take place in a flowering plant.
(ii) Write the fate of the products of double fertilization in these plants.

OR

(b) (i) Explain the structure of testicular lobules in the human male reproductive system. Name the two types of cells present in the seminiferous tubules and state their role.
(ii) Describe the role of hypothalamic hormone GnRH in spermatogenesis.

Hint:

In flowering plants, double fertilisation ensures both embryo and endosperm formation. In humans, GnRH is a master regulator of reproductive function, initiating the hormonal cascade leading to sperm production.

Answer 1

(a) (A) Double fertilisation in flowering plants: It is a unique event in angiosperms where two male gametes are involved. One male gamete fuses with the egg cell to form a diploid zygote (syngamy), and the other fuses with the two polar nuclei to form a triploid primary endosperm nucleus (PEN). This process is called triple fusion. Together, syngamy and triple fusion constitute double fertilization.
(B) Fate of products:
OR 
(b) (A) Structure of testicular lobules: Each testis has about 250 compartments called testicular lobules. Each lobule contains 1–3 highly coiled seminiferous tubules. These tubules are the sites of spermatogenesis. Two main types of cells are present:(D) Role of GnRH in spermatogenesis: The hypothalamus releases GnRH (Gonadotropin Releasing Hormone), which stimulates the anterior pituitary to secrete: