CBSE Board Class 12 - NCERT Biology (Zoology)
Chapter 4, Reproductive Health
NCERT Solutions of Chapter 4 Biology Textbook Exercise Questions
(For
Solutions of Questions 1 - 7, please click below:
Question 8: Amniocentesis for sex determination is banned in our
country. Is this ban necessary? Comment.
Solution:
Amniocentesis is a prenatal diagnostic technique, which helps us in
detecting chromosomal abnormalities, Down’s syndrome, Klinefelters syndrome, Turners
syndrome, and some other disorders of the foetus. If the foetus is found to be
suffering from an incurable abnormality then abortion before 6 months of
pregnancy is suggested.
Although amniocentesis is a useful technique in
preventing unwanted birth nevertheless it is banned because this method was more
often misused to find out the sex of the foetus leading to a steady increase in
female foeticides in India. Therefore it was necessary to ban amniocentesis to
legally check female foeticides.
Question 9: Suggest some methods to assist infertile couples to
have children.
Solution:
Infertility refers to the inability of a couple to produce a child in
spite of unprotected sexual cohabitation.
The reasons for infertility could be physical, congenital, diseases, use of
certain drugs, immunological reactions or even psychological. Specialized
health care units, called Infertility
Clinics, could diagnose the problem and give corrective treatments for many
of these problems. Following are some of the special techniques, called Assisted Reproductive Technologies
(ARTs) to help the infertile couples to have children -
Test Tube Baby
In test tube baby technique, ova from the wife or a
donor female is taken and is fused with the semen of the husband or from an
unknown donor or from a semen bank. This technique is used when the woman can
or cannot ova or when the man can or cannot produce sperm. In this technique,
the ova and the sperm are fused outside the body of the mother in a petridish
containing nutrient medium under simulated condition (as that of the body) in
the laboratory; it is called in vitro
fertilization.
The zygote obtained is electrically stimulated to
undergo cleavage and form blastomers. When 8 blastomeres are formed is
transferred into the fallopian tube, it is called Zygote Intra Fallopian Transfer (ZIFT).
Embryos with more than 8 blastomeres are transferred
into the uterus; it is called Intra
Uterine Transfer (IUT). The success rate of this technique of producing
test tube babies is less than 20 per cent.
Artificial Insemination (AI)
Artificial Insemination (AI) is a technique which is
employed when the man has impotency, coitus problem, Oligospermia, less sperm
motility or woman with infertile nature due to more anti-sperm antibodies or
defective uterus. In such a condition, the semen is collected either from
Artificial Insemination Husband (AIH) or Artificial Insemination Donor (AID) is
introduced into the vagina or into the uterus (IUI - intrauterine insemination) of the female. Semen can also be
collected from semen bank where sperms are stored at –196OC called
Cryopreservation. The sperm is introduced into the uterus or the fallopian tubes.
Gamete Intra Fallopian Transfer (GIFT)
In this technique, the gametes (ova and sperm) are
transferred into the fallopian tube of the mother. If the woman is having
Anovulation or Oligoovulation, she is injected with FSH to undergo super
ovulation (many ova produced). In woman who has a problem of picking up the ova
from the abdominal cavity, this technique is benefitted. It is also done for
man who needs AI.
If the fallopian tube of the woman is defective, IVF
is carried out by selecting the ovum and sperm leaving at a distance of 4 cm.
Later, ET (Embryo Transfer Technique) is employed.
Intra Cytoplasmic Sperm Injection (ICSI)
This is a highly costly and sophisticated technique
which requires a trained and skilled person. ICSI is based on micro manipulation
of gametes like, SUZI (Sub-zonal Injection). ICSI is effective over SUZI. In
this method, with the help of micropipette the sperm is micro-injected into the
cytoplasm of the ovum to form an embryo in the laboratory and then embryo
transfer is carried out. For this, the sperm can be collected from ejaculated
semen or TESE (Testicular Sperm Extraction) or MESA (Micro-injecting Epididymal
Sperm Abstraction).
Question 10: What are the measures one has to take to prevent
from contracting STDs?
Solution:
Diseases or infections which are
transmitted during an unprotected sexual intercourse with infected persons are
collectively called Sexually Transmitted Diseases
(STDs) or Venereal Diseases (VD)
or Reproductive Tract Infections
(RTI). The measures one has to take to prevent from contracting STDs are as
follows:
- Avoid sex with unknown or multiple partners.
- One should always use condoms during sexual intercourse.
- Maintain sex hygiene.
- If a person is in doubt he/she must consult with a qualified doctor. If STD is detected one should immediately go for complete treatment.
Question 11: State true / false with explanation.
- Abortions could happen spontaneously too.
- Infertility is defined as the inability to produce a viable offspring and is always due to abnormalities / defects in the female partner.
- Complete lactation could help as a natural method of contraception.
- Creating awareness about sex related aspects is an effective method to improve reproductive health of the people.
Solution:
- True, abortions could happen spontaneously too because of external as well as internal reasons.
- False, female partner is not always responsible for infertility. Male partner can be equally responsible for infertility whenever the sperm count or their motility is less.
- True, during complete lactation, there is no ovulation and hence no menstrual cycle so, chances of fertilization are ruled out.
- True since creating awareness about sex related aspects removes many misconceptions and confusions about sex-related problems.
Question 12: Correct the following statements:
a) Surgical methods of contraception prevent gamete formation.
b) All sexually transmitted diseases are completely curable.
c) Oral pills are very popular contraceptives among the rural
women.
d) In E.T. techniques, embryos are always transferred into the
uterus.
Solution:
a) Surgical methods of contraception are called as sterilization. These are permanent means
of contraception. These methods do not prevent formation instead they prevent
the transport of gametes.
b) Not all but, most of the sexually transmitted diseases are
curable if detected at the very early stage and treatment is done timely.
c) Oral contraceptives are small doses of progestogen and
estrogen combinations are taken orally in the form of pills. Oral pills are
popular contraceptives more among the urban women than rural women.
d) In ET (Embryo Transfer) technique, the embryo is transferred
into the uterus or to the fallopian tube depending if the embryo is more or less
than 8 blastomere stage respectively.
For Chapter 4, Reproductive Health (Question
No. 1 - 7) please visit:
CBSE Class XII, NCERT Biology - Also study:
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