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16. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit. Discuss it with your teacher.

It's called dependence and addiction. If the use or intake of alcohol is suddenly discontinued it leads to withdrawal symptoms.


7. Expand well-known abbreviations

     (e) HIV

HIV- Human Immunodeficiency Virus

 7. Expand well-known abbreviations

    (d) NACO

NACO- National AIDS Control Organisation 

7. Expand well-known abbreviations

     (c) AIDS

AIDS- Acquired Immuno Deficiency Syndrome

7. Expand well-known abbreviations.

    (b) CMI

CMI- Cell Mediated Immunity

7. Expand well-known abbreviations

   (a) MALT

MALT- Mucosal Associated Lymphoid Tissue

17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?

There are several reasons which motivate youngsters to take alcohol. Some of these are given hereunder: 1. Appreciation from friends on the use of such things. 2. Sometimes youngsters start taking these things just for pleasure 3. To get rid of depression and frustration, youngsters often move to drugs/alcohol.  4. After watching it in movies, adolescents think that taking alcohol or drugs is a...

15. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

Yes, friends can influence one to take alcohol/drugs. However, we can avoid those conditions in the following ways: 1. We should avoid the company of those friends who take drugs or alcohols. 2. We should increase our will power to stay away from these things. 3. We should have knowledge about the bad results of taking alcohols or drugs. 4. We should take the help of our parents if any question...

14. List the harmful effects caused by alcohol/drug abuse.

Harmful effects caused by alcohol/drug abuse 1. These reduce the efficiency of all the tissues of our body. Long time use of drugs and alcohol can cause many mental and physical diseases. 2. These dilate the blood vessels and affect the normal functioning of the heart. 3. Excessive drug/alcohol abuse can lead to cirrhosis in the liver. 4. Excessive drug/alcohol abuse may increase the workload...

13. Explain what is meant by metastasis.

Metastasis- It refers to the process of formation of secondary tumors from the fragments of primary tumors. The pieces of primary tumors are carried to neighbouring tissues via blood. Metastasis is the last stage of cancer.

12.  How is a cancerous cell different from a normal cell?

Differences between cancerous cells and normal cells Cancer cells   Normal cells Cancerous cells divide at a faster rate forming a mass of cells called tumour Normal cells divide at a normal rate and do not cause the formation of tumors They spread, move to another tissue and affects their normal functions. Thus, they are not restricted to one location These are restricted to one...

11. What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?

AIDS is a viral disease caused by the HIV virus. It is considered to be one of the most dangerous diseases with no cure until now. HIV affects the immune system of the body and makes it unable to perform its usual functions. The mechanism by which HIV virus causes deficiency of the immune system is as follows: 1. After entering into the system, HIV binds itself to the surface receptors present...

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

Acquired immunodeficiency syndrome is caused by the human immunodeficiency virus. The various routes by which transmission of human immunodeficiency virus takes place are: 1. Through sharing of infected needles. 2. Having sex with an infected person without using condoms. 3. Infected mother to baby through the placenta. 4. Through the transfer of blood from an infected person to normal person

9. Draw a well-labelled diagram of an antibody molecule.

The well-labelled diagram of an antibody molecule is as follows:  

8. Differentiate the following and give examples of each:
   (b) Active and passive immunity

Active immunity      Passive immunity  Active immunity develops in a person’s own body in response to an infection or any disease Passive immunity develops in a person's body when antibodies from outside are injected into the body Active immunity does not have side effects It may have side effects It is long lasting It has a short span Active immunity takes a long period...

8. Differentiate the following and give examples of each:

   (a)     Innate and acquired immunity

 Innate immunity Acquired immunity      It is a non-specific type of defence present at the time of birth and provides different kinds of barriers to the entry of foreign agents into the body. It is pathogen specific defence characterised by memory.   It remains throughout the life  It is short- lived  Innate immunity is inheritable Acquired immunity is not inheritable   

6. Name the primary and secondary lymphoid organs.

Lymphoid organs are the organs in which origin, maturation and proliferation of lymphocytes occur. Lymphoid organs are of two types i.e. primary lymphoid organs and secondary lymphoid organs. In primary lymphoid organs, the origin of lymphocytes occurs. These include bone marrow and thymus. After maturation, lymphocytes migrate to a secondary lymphoid organ like spleen, lymph nodes, tonsils,...

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

A suitable gene means that special DNA segment which can be injected into the host body to produce specific proteins. These specific proteins should be such that they can kill the particular disease-causing organism present in the host body.

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


Drinking contaminated water is one of the main reason for water born diseases such as typhoid, cholera etc. The measures that can be taken to prevent water-borne diseases are as follows 1. To prevent these diseases we should dispose of sewage, excreta etc. properly. 2. We should check our water reservoirs regularly. 3. We should consume clean, pure, contamination free water only. 

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

   (D) Pneumonia

Pneumonia- It transmits through droplet infection i.e. through a sneeze, cough, sharing utensils etc.