Meiosis is an essential event in the sexual cycle of any organism because:
(i) It maintains the number of chromosomes fixed (2n) from generation to generation. Haploid gametes are formed as a result of meiosis. Diploid (2n) condition is restored during fertilization.
(ii) It increases the genetic diversity and variation due to crossing over between homologous chromosomes and their random segregation.

(a) A meiocyte is diploid cell, while a gamete is haploid.
(b) A whiptail lizard develops from the female gamete, without fertilisation; hence it is parthenognetic.

Cut is an intra-uterine device (IUD) and functions as follows:
1. It suppresses sperm motility and the fertilising capacity of sperms.
2. It increases phagocytosis of sperms within the uterus.

Colostrum refers to the milk that comes out of the mammary glands of the mother during the initial few days of lactation following partuirition.
It contains several antibodies,which are essential for developing resistance in the new born babies;hence the breast-fed babies are likely to be healthy.

1. Since geitonogamy involves two different flowers of the same plant, it is genetically similar to autogamy; both autogamy and geitonogamy do not result in genetic variation in the progeny.
2. Geitonogamy and cross-pollination involve different flowers and a pollinating agent.

Yes, breast feeding is one of the natural contraceptive methods. It reduce fecundity by affecting the production of certain reproductive hormones. It is known to suppress the production of Gonadotropin Releasing Hormone (GnRh) and Follicle Stimulating Hormone (FSH).
The release of these hormones triggers ovulation. Breast feeding also leads to increased level of prolactin, a hormone that inhibits ovulation.
So, even when a woman ovulates, her likelihood of conceiving is low if she is breast feeding.

(a) Scutellum
(b) Epicotyl
(c) Polyembryony
(d) Patrhenocarpic fruits.

(a) Ovary is superior
(b) Flower is hypogynous because all the floral arise from thalamus below the level of ovary
(c) Ovule is anatropous because it is completely inverted. The micropyle is near the hilum and faces down towards the placenta.The embryo sac is straight.
(d) The ovary of the flower gets converted into fruit after fertilization.
(e) A = Stigma, B = Style, C = Ovary and D = Ovule 

(i) Oogenesis
(ii) Clitoris
(iii) Mesometrium
(iv) Tubectomy
(v) Estrogens
(vi) Female rabbit

(i) d,f (ii) e,g (iii) a (iv) b (v) c

(i) a- Spermatogonia
 b-Interstitial cells or Leydig cells
 c-Spermatozoa.
(ii)a-Spermatogonia produce the spermatozoa (sperms).
 d-Sertoli cells provide nutrition to the germ cells.

In wind pollinated flowers,
(i) The stamens are well-exposed, so that pollen grains are easily dispersed in wind currents.
(ii) The stigma is large and often feathery, to easily trap the air-borne pollen grains.
(iii) The pollen grains are light and non-sticky, to be transported in wind currents.
(iv) Pollen grains are produced in enormous quantity.
(v) Numerous small flowers are packed into an inflorescence.
(vi) There is a single ovule in the ovary of these flowers.

(i) Test tube baby programme - In this method, the ovum of the woman and the sperm of her husband or a donor, are made to fuse ,under laboratory conditions; it is called in vitro fertilisation (IVF). - The zygote or early embryo is implanted in the fallopian tube or uterus respectively for further development.
(ii) Intra Cytoplasmic Sperm Injection (ICSI) - In this method, the sperm is injected directly into the ovum to form the zygote and then embryo transfer is carried out.
(iii) Gamete Intra Fallopian Transfer (GIFn - This method involves the transfer of an ovum collected from a donor female into another female for fertilisation and further development of foetus.
(iv) Artificial insemination - In this method, the semen collected from the husband or a healthy XII donor, is artificially introduced into the vagina or into the uterus (intra uterine insemination). - It is carried out when infertility is due to the inability of the male partner to inseminate the female or due to very low sperm count in the semen.

(a) Development of female gametophyte: The female reproductive part of a flower is gynoecium, which consists of three parts-stigma, style, and ovary. The ovules are formed in the ovary and attach to it through placenta. The ovule is surrounded by one to two protective layers are called integuments leaving a small opening at one end termed as a micropyle. The stalk of the ovule is called funiculus.The ovule is composed of multi-celled cellular tissue called the nucellus. A hypodermal cell of nucellus toward at the micropylar end enlarges and becomes a megaspore mother cell that undergoes meiosis to form a linear tetrad of four megaspores. Out of four, only one remains functional and three megaspores degenerate. The functional megaspore undergoes three successive mitotic divisions to form eight nuclei, which arrange themselves into three groups. Three: nuclei migrate towards the micro-pylar end and form the egg apparatus. Other three nuclei form antipodal cells at chalazal end. The remaining two nuclei come together as polar nuclei which fuse to form secondary nucleus in the centre of the embryo sac.
(b) Role of endothecium: Microsporangium generally surrounded by wall layers like epidermis, endothecium, 2 or 3 middle layers and the tapetum. Endothecium performs the function of protection and helps in dehiscence of anther to release the pollen
Role of tapetum: It nourishes the developing pollen grains.

Functions : Sertoli cells - secrete factors which help in the process of spermiogenesis/provide nutrition to germ cells.
Spermatogonia - divide to produce spermatids / sperms.
Leydig cells - synthesis or secretion of androgens / testosterone.
(b) Pituitary hormones - LH (luteinising hormone) - acts on Leydig cells and stimulates synthesis and secretion of androgens.
FSH/follicIe stimulating hormone - acts on sertoli cells and simulates secretion of some factor that help in spermiogenesis.
Sex hormone - (Androgen/testosterone) stimulate process of spermatogenesis.

(i) A sperm consists of a head, neck, middle piece and a tail.
(ii) Middle piece  It is cylindrical and known as the power house of the sperm. It possesses many mitochondria to produce energy for the movement of the tail that facilitates sperm motility essential for fertilisation.
(iii) He is curious, intelligent, inquisitive and has scientific attitude.

(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.

(i) One can know the sex of the foetus by amniocentesis.
(ii) During the process of amniocentesis, a sterile needle is inserted through the abdominal wall into the amniotic sac. Then, a small amount of amniotic fluid is withdrawn through the needle.
The fluid contains cells, which are separated from the amniotic fluid. Tests are then performed on cultured cells by chemical analysis, DNA analysis, and chromosomal analysis.
(iii) Disclosing the sex of the foetus is banned in our country because, in the past, there have been numerous cases, where the female foetud has been aborted. this discrimination for the girl child is considered a crime. the number of females to males ration is thereby reduced.
(iv) the doctor is devoted to his duties and has professional and moral ethics.

Due to change in lifestyle and eating habits, many couples are suffering from infertility, nowadays, i.e. they are not able to conceive. Infertility may occur in both man and woman.
In order to solve the problems related to infertility, the advancement in technologies has come to the rescue.
Sperm donation has become a boon for the couple, who suffer from infertility and want their own child.
Sperm donation is helpful in following cases in males:
(i) When sperms are blocked by an abnormality in the epididymis and in the testis.
(ii) Sexual dysfunction.
(iii) The absence of sperms in males.

A typical microsporangium is surrounded by four wall layers, i.e. the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers are protective in function and help in dehiscence of anther to release pollen grains.
The innermost layer (tapetum) nourishes the developing microspores or pollen grains. The cells of tapetum possess dense cytoplasm and generally have more than one nucleus.

When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium.