question_answer

Which process help the sperms to gain entry into female oocyte during fertilisation? Mention the significance of the point of entry of sperm.

Or

Differentiate between the following.

(i) Gametogenesis and embryogenesis

(ii) Oestrus cycle and menstrual cycler

Answer:

The sperms in the female tract are made capable of fertilising the ovum by secretions of female genital tract. This process is called sperm activation or capacitation. The capacitated sperms release sperm lysin from the acrosome which contains hyaluronidase enzyme. This enzyme helps to digest the hyaluronic acid by which cells of corona radiata remain glued together, so that the sperm can penetrate the oocyte. After the penetration of a sperm into the cell membrane of oocyte, the zona pellucida becomes impervious to other sperms and thus, polyspermy is prevented.
The point of entry of sperm's head into the ovum is of great significance. It is the area which extrudes the polar bodies. This area is called animal pole. It decides the polarity and first cleavage of the zygote, which is along the animal - vegetal pole.
Or
(i) Differences between gametogenesis and embryogenesis are as follows
Gametogenesis	Embryogenesis
It is the process of development of gametes from the meiocytes.	It is the process of development of embryo from the zygote.
It is a pre - fertilisation event.	It is a post - fertilisation event.
It involves meiosis.	It involves mitosis and cell differentiation.
(ii) Differences between oestrus and menstrual cycle are as follows
Oestrus cycle	Menstrual cycle
The cyclic changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase of non - primate mammals is called oestrus cycle.	The cyclic changes in the activities of ovaries and accessory ducts as well as hormones during the reproductive phase of primate mammals is called menstrual cycle.
Females show strong irresistible sexual urge.	Females do not show irresistible sexual urge.
There is heat production at the time of ovulation and copulation occurs only at that period.	There is no heat period and copulation can occur during anytime of the cycle.
The shedding of endometrium and bleeding does not occur, e.g. cows, sheep, rats, deers, dogs, tigers, etc.	The shedding of endometrium and bleeding occurs, e.g. monkeys, apes, humans, etc.