Question

Give reasons for the following: (i) Why can a woman generally not conceive a child after 50 years of age? (ii) Polar bodies are formed during oogenesis and not during spermatogenesis.

Study the figures given below showing initial stages in the formation of female gametophyte and answer the questions that follow. (i) Identify (P) and (Q). (ii) I. What kind of division does cell (P) undergo to form (Q)? II. How many (Q) cells form the embryo sac? What is the name given to such kind of development? III. How many free nuclear mitotic divisions will the functional megaspore undergo to form the embryo sac? IV. Describe the structure of a mature female gametophyte.

How is triple fusion achieved in these plants ?

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.