Give reasons: a. Placenta is extremely essential for foetal development. b. Blocking of vas deferens prevents pregnancy. c. Wind acts as a pollinating agent. d. Use of condoms prevents pregnancy. e. Blocking of Fallopian tubes prevents pregnancy.
Answers
Answer:
Ans. (i) Placenta is extremely essential for foetal development because it helps in nutrition, respiration, excretion, etc., of the foetus through the maternal supply.
(ii) Blocking of vas deferens prevents passage of sperms, hence, there is no fertilisation thus preventing pregnancy.
(iii)Wind acts as a pollinating agent because it helps in transfer cf pollen grains from anther to stigma of a flower.
(iv)Condoms prevent entry of sperms into vagina, hence preventing pregnancy.
(v)If Fallopian tube is blocked, sperm and egg do not meet and fuse and fertilisation does not take place.
Answer:
(i) The placenta is an organ found only in mammals during development of foetus. It is made up of cells derived from both mother and foetus.
Placenta allows the exchange of materials between mother and foetus.
It allows the transfer of nutrients and oxygen from mother to foetus.
Waste products excreted by the foetus like urea, uric acid and even carbon dioxide are diffused to maternal blood stream by the placenta.
Antibodies pass through the placenta that provides immunity to the foetus.
Placenta secretes several hormones that are essential for foetal development.
These above mentioned reasons prove that placenta is extremely essential for foetal development.
(ii) In male reproductive system, vas deferens is a straight long tube which carries sperms produced in testes to the urethra. If this vas deferens is blocked, the sperms cannot reach to the semen. Thus, the semen produced by the person will be without sperm. Without sperm fertilization will not occur. Vasectomy is a type of sterilization process for man in which the vas deferens is cutted and tied.
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