Biology Class 12 NCERT Solutions: Chapter 8 Human Health and Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 3 How does the transmission of each of the following diseases take place?

(a) Amoebiasis

(b) Malaria

(c) Ascariasis

(d) Pneumonia


Table of Mode of Transmission


Mode of transmission
a.AmoebiasisEntamoeba histolyticaIt is a vector-borne disease that spreads by the means of contaminated food and water. The vector involved in the transmission of this disease is the
b.MalariaPlasmodium sp.It is a vector-borne disease that spreads by the biting of the female Anopheles
c.AscariasisAscaris LumbricoidesIt spreads via contaminated food and water.
d.PneumoniaStreptococcus PneumoniaIt spreads by the sputum of an infected person.

Q. 4 What measure would you take to prevent water-borne diseases?


  • Water-borne diseases such as cholera, typhoid, hepatitis B, etc. spread by drinking contaminated water.
  • These water-borne diseases can be prevented by ensuring proper disposal of sewage, excreta, periodic cleaning.
  • Also, measures such as disinfecting community water reservoirs, boiling drinking water, etc. should be observed.
Water Borne Diseases

Q. 5 Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.


  • A ‘suitable gene’ refers to a specific DNA segment which can be injected into the cells of the host body to produce specific proteins.
  • This protein kills the specific disease causing organism in the host body and provides immunity.

Q. 6 Name the primary and secondary lymphoid organs.


  • Primary lymphoid organs include the bone marrow and the thymus.

Secondary lymphoid organs are the spleen, lymph nodes, tonsils, Peyer՚s

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