Fertilisation in human beings takes place in the ampullary isthmic junction of the Fallopian tube.
The events/steps of fertilisation are as follows.
   Discharge of semen in female vagina
                                \(\downarrow \)
Movement of sperms to reach ampullary-isthmic junction of Fallopian tube
                                \(\downarrow \)
Release and transport of ovum at the same junction
                                \(\downarrow \)
                  Formation of zygote

1. Lactational Amenorrhoea refers to the absence of menstriation during the period of intense lactation following parturition.
2. It is because ovulation and other events in menstrual cycle do not occur during this period.
3. Hence as long as the mother breast feeds her child chances of conception are almost nil.

(i) It is a non-steroidal preparation.
(ii) It is a 'once' a week' pill.
(iii) It has high contraceptive value.
(iv) It has fewer side effects than other oral contraceptives.

Parturition is initiated by the foetal ejection reflex,a neural mechanism of mild contractions of the uterus,initiated by the fully developed foetus and placenta.
It triggers the release of oxyticin from material pituitary,which causes stronger contractions of uterine muscles and stimulates more secretion of oxytocin.
The stimulatory reflex between uterine contractions and secretion of oxytocin continues and results in parturition,i.e.the delivery of the baby;hence it is called an neuro-endocrine mechanism.

Advantage
1. Since cleistogamous flowers are autogamous, there is an assured seed-set.
Disadvantage
1. Continued self-pollination leads to inbreeding depression.

(a) Female partner is blamed due to social mind set/inequality of sexes/lack of awareness/male dominated society/any other relevent point.
(i) Awareness to be created that abnormality can occur in both male and females and infertility issues with suitable examples.
(ii) Mutual respect towards both the partners in case of the problem and to find the remedy from medical experts instead of visiting quacks.
(iii) Educate them to find the reason and not believe in superstitions.
(b) Physical (abnormality in reproductive system), congenital, immunological or psychological.
(c) Intra cytoplasmic sperm injection (ICSI)/artificial insemination (AI)/Intra uterine insemination (IUI).

(i) To understand the problem faced by the family and the nation due to increasing population and the benefits of having a small family.
(ii) Role of Government in controlling population explosion are:
(a) Creating public awareness through mass media.
(b) Education at all Levels.
(c) Family planning.
(d) Increasing marriageable age (18 for girls and 21 for boys)
(iii) In India, these programmes called 'family planning' were initiated in 1951.
(iv) Rohit and his friends showed understanding about the problem of population explosion, teamwork, and motivational capacity.

Fertilisation is the fusion of two gametic nuclei to form a diploid zygote.It involves a series of chemical and physical steps as follows:

The cortical cytoplasm of ovum shows the physicochemical reactions called the cortical reactions.

1.Sperm lysins dissolve the membranes around egg.centriole physically passes into ovum.

3.Normally these reactions result in the formation of fertilisation membrane outside the egg plasma membrane.

4.In man, cortical granules burst and release their contents between egg plasma membrane and zona pellucida i.e. perivitelline space (No fertilisation membrane formation).The plasma membrane shows increased permeability for water, phosphate and potassium.

5.Electrical potentiality of plasma membrane changes from positive to negative, NAD kinase enzyme becomes activated after fertilisation for the oxidation and reduction reaction of the cell.

6.Rate of DNA synthesis increases with great pace after fertilisation.Hence the ovum is now ready for mitosis(cleavage).

7.Cleavage results in multicellular in dividual.

Spermatogenesis is under the control of endocrine hormones. In human male reproductive system, spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin-releasing hormone by hypothalmus. The increased level of GnRH then acts on the anterior pituitary gland and stimulates secretion of the two gonadotropins : Luteinising hormone (LH) and follicle stimulating hormone (FSH). LH acts on leydig cells and stimulates synthesis and secretion of androgens, like testosterone which stimulates spermatogenesis. FSH acts on the sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis. Excess of testosterone inhibits the secretion of LHP and GnRH. A glycoprotein called inhibin supresses FSH synthesis. Thus normal release of testosteron is under negative feed back control.

Exine: It can withstand high temperature/strong acids/alkali. It protects pollens.
Intine: It is a thin and continuous layer made up of cellulose and pectin. The intine produces pollen tube.
Vegetative cell: It is bigger and has abundant food reserve.
Generative cell: It divides mitotically to give rise to two male gametes

(i) Medical Termination of Pregnancy-Intentional or voluntary termination of pregnancy before full term with help of an expert doctor is called MTP
(ii) (a) MTP is advised in the following situations-(i) when there is unwanted pregnancy.
(b) When continuation of pregnancy is harmful or fatal to either mother or foetus or both.
(c) When there is failure of contraceptive used during coitus or rapes in either case it is advisable to go for MTP during first trimester
 i.e., up to 12 weeks of pregnancy.
(d) MTP is also advised if the foetus suffers from incurable genetic and metabolic disorder.
(iii) Amniocentesis is a prenatal technique of studying genetic disorders of foetus by taking out anniotic fluid. But however amniocentesis and MTP has been misused for knowing the sex of the foetus and destroying the same if the foetus is female.

The modes are reproduction are listed below:
1.Bryophyllum: Reproduce asexually by formation of marginal adventitious buds in mature leaves.
2.Potato: Buds in the eyes in potato tuber grow to form aerial shoots.
3.Yeast: Budding.
4.Rhizopus: Sporangiospores formed inside sporangia.
5.Penicillium: Conidia formed on conidiophores.