(a) (i) Explain the following phases in the menstrual cycle of a human female: (1) Menstruation (2) Follicular phase (3) Luteal phase (ii) 'A proper…

(1)Menstruation phase – This flow is due to breakdown of endometrium lining of uterus and blood vessels along with unfertilized ovum continues for $\displaystyle 3$-$\displaystyle 5$ days. This happens when ovum is not fertilized.

Follicular phase – In this phase follicle develops into mature

Graafian Follicle. This is known as proliferative phase because endometrium lining regenerates. It last for $\displaystyle 10$ days.

Luteal phase – This phase lasts for about $\displaystyle 10$-$\displaystyle 14$ days. This is also known as secretory phase. In this phase corpus luteum is formed which secretes large amount of progesterone that is required for maintenance of pregnancy.

• Yes,

• Chances of fertilization are nil if abstain from Coitus from day

$\displaystyle 10$-17th day of menstrual cycle.

• The embryo development starts only after a certain amount of

endosperm is developed because it is an adaptation for assured nutrition to the developing embryo thus endosperm development precedes embryonic development

• To provide nutrition to the embryo.

Stages in embryo development in a dicot: Zygote → Globular Embryo → Heart-Shaped Embryo (with Suspensor) → Mature embryo (Radicle, Cotyledon, Plumule).