(i) Horne 'X' is Luteinising Hormone (LH) and 'Y' is Follicle Stimulating Hormone (FSH).
(ii) (a) Follicular phase (proliferative phase).
(b) Ovulatory phase (release of ovum) followed by luteal phase.
(c) Luteal phase.
(iii) (a) FSH is secreted by the anterior pituitary, which stimulates the ovarian follicle to secrete oestrogen, which in turn stimulates the proliferation of the endometrium of the uterine wall.
(b) Both LH and FSH attain a peak level in the middle of cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle is called LH surge. It induces rupture of Graafian follicle and thereby the release of ovum (ovulation). Due to these events, this phase is termed as evulatory phase of menstruate cycle.
(c) The remaining cells of ovarian follicles are stimulated by the LH to develop corpos luteum. The corpus luteum secretes large amount of progesterone, which is essential for the maintenance of endometrium. This is known as luteral phase.

The menstrual cycle is controlled by rhythmic synthesis and release of ovarian hormones under feedback control from the hormones of anterior pituitary. These are discussed below:
(i) Pituitary hormones The gonadotroph cells, of anterior pituitary secrete FSH and LH in females. Their role in menstrual cycle are:
(a) Follicle Stimulating Hormone (FSH) It is secreted during the follicular phase of the cycle and is responsible for follicular development on induction of LH receptors on granulosa cells of the ovary.
(b) Luteinising Hormone (LH) Its primary function is to stimulate the formation of corpus luteum and secretion of estradiol and progesterone from ovary.
(ii) Ovarian hormones Ovary secretes the following hormones under the effect of FSH and LH.
(a) Oestrogen It influences proliferation of the uterine endometrium to prepare for implantation of the fertilised oocyte.
(b) Progesterone secreted from corpus luteum under LH influence, maintains endometrium for implantation It rising level inhibits LH.

(i)  Yes, It effects not only health of smoker but also persons around the smoker.
(ii)  Smoke contains toxic gasses and tar which is not good for health and may cause cancer of oral cavity and respiratory.
(iii)  Long use of tobacco product may damage the genetic material and as a result malformed infants may be formed in women who use tobacco products regularly.

Structure of Epithelio-chorial placenta. Epithelio-chorial placenta is the simple and basic type of placenta as formed in cow, goat etc. In this case some of the components are derived from the uterine wall of mother while the other parts are derived from the foetus itself.

The maternal components of placenta are:
1. Mucous membrane of the uterine wall.
2. Uterine connective tissue.
3. Maternal endothelium (wall of maternal blood capillaries).
Foetal components of placenta are:
1.Wall of foetal blood capillaries.
2. Foetal connective tissue.
3. Foetal chorionic epithelium

A fertilised egg divides mitotically to form number of cells.These cells show morphogenetic movements to arrange themselves in three germinal layers.This arrangement initiates the phases of differentiation and specialisation.Different groups of cells of a particular germinal layer change their shape and get differentiated into structure or organs of the individual.All the cells with different organs(brain, eye, heart, skin etc).

Thus it is quite clear that fertilised egg is blueprint for future development.Fertilised egg contains genetic information from both the parents.It is stored in DNA.During differentiation, the characters are expressed as a result of sequence of events.Precisely every fertilised egg is specific blueprint for development of particular animal.

Formation of three germ layers in a mammalian embryo.The blastodermic vesicle is surrounded by outer cellular
layer(trophoectoderm).The blastodermic vasicle shows internal cluster of cells due to differentiation.This cluster of cells is called inner cell mass.Now the morphogenetic movements(epiboly,emboly etc.)of the cells in small masses or sheets take place.As a result three germinal layers (i.e.endoderm, mesoderm and ectoderm) are formed.
Formation of Endoderm.
 Some cells from the inner cell mass detach.Cells move in sheets or masses in the blastocoel.Cells move in sheets or masses in the blastocoel.These are the potential endodermal cells.These cells arrange themselves as second layer inner to outer layer of blastodermic vesicle.The blastocoel disappears and a new cavity appears.This new cavity is called archenteron or primitive gut.This archenteron will give rise to gut tract.
Formation of Mesoderm. At the margin of the embryonic disc, cells multiply at the increased rate.The thickness of the embryonic disc increase.These cells detach from the embryonic disc and give rise to mesoderm.
Formation of Ectoderm. After the formation of mesoderm, the cells of the embryonic disc arrange themselves so as to form the ectoderm.

Cleavage is holoblastic type but there is tendency to show size differences of the blastomeres from the very start. Cleavage occurs during its passage through fallopian tube to uterus.

The first cleavage takes place in the cytoplasm of ovum on an imaginary axis (Animal pole to vegetal pole). The first division results into two blastomeres. One blastomere is slightly larger than the other. The larger cell divides first and thus forms the three blastomeres. Then the smaller blastomere divides and thus four blastomeres are formed. It is 4 celled stage.
2nd cleavage is at right angle to the 1st cleavage. One member of the large blastomeres of 4-cell stage divides forming 5-cell condition followed 6-7 stage ultimately 8 celled stage. Successive cleavage divisions result in the formation of solid mass of cells. Thus solid ball-like stage is called morula stage.
Conversion of morula into blastula is initiated by dynamic rearrangement of small blastomeres. A central fluid filled cavity called blastocoel (segmentation cavity) appears. Externally placed blastomeres lose their rounded form and become flat. This trophoblast along with lining of uterus forms extra-embryonic membranes. This provides protection and nourishment to the developing embryo.

Simultaneouslyzonapellucidadisappears and embryo gets implanted to the uterus. Below the blastodermic vehicle there appears formative tissue i.e. inner cellmass. From this inner cell mass, proper embryo is formed.

Hormonal Control of Menstrual Cycle.
Gonadotropin-releasing hormone (GnRH) also called Gonadotropin-releasing Factor (GnRF), is secreted by the hypothalamus of the brain, which stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).FSH stimulates the ovarian follicles to produce oestrogens during proliferative phase.LH stimulates the corpus luteum of the ovary to secrete progesterone.
1.Menstrual phase is caused by the reduction of progesterone and oestrogens.
2.Proliferative phase is caused by the increased production of oestrogens.
3.LH causes ovulation.
LH also causes transformation of empty Graafian follicle into corpus luteum by luteinisation inside the ovary. LH also stimulates corpus luteum to secrete progesterone hormone to help in implantation, placentation and maintenance of pregnancy.
4.Secretary phase is caused by increased production of progesterone.

(a) sexually
(b) viviparous
(c) internal
(d) haploid
(e) diploid
(f) ovulation
(g) luteinising hormone
(h) syngamy
(i) ampullary-isthmic junction
(j) blastula
(k) umbilical cord.

(a) False
Androgens are formed by Leydig cells.
(b) True.
(c) False
Oogenesis takes place in the ovarian follicles.
(d) True
(e) False
Oogenesis occurs in the female embryo before birth but does not complete until puberty.
(f) True.
(g) True.