Because
(i) Mothers milk is a perfect diet for neonates and young infants.
(ii) Mother milk has antibodies(lgA,lgG) and several biochemicals for providing resistance against several pathogens.
(iii) Mother provides phagocytes to the baby for killing germs.
(iv) Breastfeeding is a natural method for preventing another pregnancy soon after.

1. Surgical procedures block gamete transport and thereby prevent conception.
2. Sterilisation procedure in human males is called vasectomy; in this method a small part of the vas deferens is removed or tied up through a small incision on the scrotum.

(i) In mullticellular organisms, cells/ tissues are specialised for various functions; the function of reproduction is performed by one group of speciallised cells.
(ii) Not all cells of a multicellular organism retains the power of division at maturity; the cells which retain the power of division are localised and they alone can help in reproduction.

Primary endosperm cell forms the kernel of coconut.
Difference
The kernel of coconut is the cellular endosperm, while the coconut water is the free-nuclear endosperm.

1. It is difficult to get rid of them because they propagate vegetatively at a rate faster than we could remove them.
2. It drains oxygen from the water.
3. It leads to fish mortality, i.e. death of fishes.

1. In crop breeding programmes, pollen grains from the selected male parent only are used.
2. So, to prevent contamination of the stigma of the unisexual/female flower, they are bagged.

Pollen grains are best preserved as fossils because of the following reasons:
(i) The sporopollenin of exine is highly resistant to the action of strong acids and alkali and can withstand a high temperature.
(ii) It is not easily degraded by any of the enzyme known so far.

(a) User friendly, no side effect, reversible, effective, should not interfere with sexual drive desire of the user, easily available.
(b) Copper T/ Multiload 375

(a) Motivate smaller families.
(b) Use media/poster showing a happy couple with two children with slogan 'hum do hamare do'.
(c) Statutory raising of marriageable age of the female to 18 years and male to 21 years.

Difference between vasa efferentia and vasa deferentia are as follows

Formation of the parts in a fruit areas follows:-

T.S.of Ovary

The target cells for luteinising hormone in males are the Leydig cells and in females are the mature follicles.

LH in males stimulates the Leydig cells of testes to secrete androgens (testosterone) which controls spermatogenesis.

LH in females stimulates ovulation formation of corpus luteumfrom the reptured follicle and secretion of progesterone by corpus luteum.

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.

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.

Development of Female Gametophyte:
- The megaspore mother cell undergoes meiosis to form four megaspores.
- Three of them degenerate and the functional megaspore enlarges to form the embryo sac.
- Its haploid nucleus undergoes a mitotic division and the two daughter nuclei move towards the poles.
- Each of them undergoes two successive mitotic divisions.
- Cell wall formation starts in the 8-nucleate stage.
- Three of them at the micropylar end form the egg apparatus, consisting of a female gamete and two synergids.
- Three of them at the chalazal end form the antipodal cells.
- One nucleus from each of the poles moves to the centre; they are called polar nuclei.
- The two polar nuclei fuse in the centre (now the central cell) to form a diploid secondary nucleus.
- Thus, the mature embryo sac is 7-celled and 8-nucleate.