question_answer

Discuss the various chemical methods of controlling human population.

OR

What do you mean by gametogenesis? Describe the structure of a human sperm.

 

Answer:

Chemical methods of controlling human population are following:

(a) Birth control pills are taken through mouth. They contain combination of progestogens and estrogen. Pills are taken daily menstruation occurs) it has to be repeated in the same pattern till the female desires to prevent conception. They inhibit ovulation and implantation.

(b) Progestogens alone or in combination with estrogen is used as by female injections or implants under the skin of the upper arm. Their mode of action is same as that of pills and their effective period lasts for 3 to 4 years.

(c) Spermicidal creams, tablets, jellies and paste are introduced in the vagina before the sexual intercourse. These kill sperms.

OR

Gametogenesis carried out in gonads, is the formation of gametes for sexual reproduction. It is controlled by gonadotrophic hormones (FSH, LH, ICSH etc.) secreted by pituitary gland. Meiosis is the most significant part of the of gametogenesis. The male reproductive organ or testis undergo spermatogenesis and the female reproductive organ or ovary, oogenesis. As a result of reduction division or meiosis, the sperms and the ova produced have only half the number of chromosomes as compared to body cells of the parent.

Human sperm is microscopic in structure. It is composed of head, neck, middle piece and tail. The whole sperm is covered by a plasma membrane. The head portion has an elongated nucleus whose anterior portion is covered by a cap like acrosome. The acrosome is derived from the Golgi complex & contains hydrolysing enzymes for the sperm penetration. The nucleus contain haploid set of chromosomes. The middle piece has several mitochondria which provide energy for sperm movement. The tail helps in motility of sperm.