Biology Class 12 NCERT Solutions: Chapter 8 Human Health and Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 7 The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:

(a) MALT

(b) CMI

(c) AIDS

(d) NACO

(e) HIV


(a) MALT – Mucosa- Associated Lymphoid Tissue

(b) CMI – Cell -Mediated Immunity

(c) AIDS – Acquired Immune Deficiency Syndrome

(d) NACO – National AIDS Control Organization

(e) HIV – Human Immune Deficiency virus

Q. 8 Differentiate the following and give examples of each:

(a) Innate and acquired immunity

(b) Active and passive immunity


  1. Innate and acquired immunity
Image of Innate and Acquired Immunity
Innate immunityAcquired immunity
1.It is a non − pathogen specific type of defense mechanism.1.It is a pathogen specific type of defense mechanism.
2.It is inherited from parents and protects the individual since birth.2.It is acquired after the birth of an individual.
3.It operates by providing barriers against the entry of foreign infectious agents.3.It operates by producing primary and secondary responses, which are mediated by B – lymphocytes and T-lymphocytes.
4.It does not have a specific


4.It is characterized by an immunological
  1. Active and Passive Immunity
Image of Active and Passive Immunity
Innate immunityAcquired immunity
1.It is a type of acquired immunity in which the body produces its own antibodies against disease-causing antigens.1.It is a type of acquired immunity in which readymade antibodies are transferred from one individual to another.
2.It has a long lasting effect.2.It does not have long lasting effect.
3.It is slow. It takes time in producing antibodies and giving responses.3.It is fast. It provides immediate
4.Injecting microbes through vaccination inside the body is an example of active immunity.4.Transfer of antibodies present in the mother՚s milk to the infant is an example of passive immunity.

Q. 9 Draw a well – labelled diagram of an antibody molecule.


Antibody Molecule

Q. 10 What are the various routes by which transmission of human immunodeficiency virus takes place?


AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human immunodeficiency virus (HIV) .

It has the following modes of transmission:

  • Unprotected sexual contact with an infected person.
  • Transfusion of blood from a healthy to an infected person.
  • Sharing infected needles and syringes.
  • From an infected mother to a child through the placenta.

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