Q. 29

Explain the proce

Answer :

a) The process of rupture of graffian /tertiary follicle and the release of ovum is known as ovulation. It takes place in the mid of the cycle i.e. approx. at 14th day, due to LH surge.

b) The process of fusion of male gamete (sperm) and female gamete (ovum) and formation of Zygote is known as fertilisation. It takes place at ampulla– isthmus junction.


c) Implantation is the process of attachment of the zygote in blastocyst stage to the endometrial layer of the uterus. The attachment on the endometrial layer is by the trophoblast cells of the blastocyst.


OR


a) The anther also known as Microsporangium is surrounded by 4 wall layers :-


1) Epidermis


2) Endothecium


3) Middle Layer


4) Tapetum


The outer three layers i.e. epidermis, endothecium and middle layer have the function of protection and dehiscence.


The innermost layer i.e. the tapetum nourishes the developing pollen grain.


b) Once the pollen tube reaches the synergid it releases 2 male gametes. One male gamete fuses with egg cell and other male gamete fuses with polar nuclei.


When the male gamete fuses with egg cell it is called as syngamy thus leads to formation of zygote.


When the male gamete fuses with polar nuclei it forms Primary Endosperm Nucleus (PEN). It is formed by triple fusion.


Both the fusions together are called as Double fertilization.


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