These Solutions are part of NCERT Solutions for Class 12 Biology. Here we have given NCERT Solutions for Class 12 Biology Chapter 8 Human Health and Diseases
Question 1.
What are the various public health measures, which you would suggest as a safeguard against infectious diseases?
Solution:
Prevention and control of infectious diseases
I. For water-borne diseases like typhoid, amoebiasis, etc.
Practice personal and public hygienic measures.
a. Personal hygienic measures
b. Public hygienic measures
II. For air-borne diseases like common cold, pneumonia
III. For vector-borne diseases like malaria
The use of vaccines and immunization programmes has enabled us to eradicate smallpox. Diseases like polio, diphtheria, tetanus etc. have been controlled to an extent by the use of vaccines. Nowadays biotechnology is focussing on the preparation of newer and safer vaccines. A large number of antibiotics are available to treat many infectious diseases.
Question 2.
In which way has the study of biology helped us to control infectious diseases?
Solution:
Study of biology has helped us to know about causes of diseases, carriers of diseases (vectors), effects of diseases on different body functions and above all, means to control diseases. Our immune system plays a major role in preventing diseases.
Question 3.
How does the transmission of each of the following diseases take place ?
Solution:
Question 4.
What measure would you take to prevent water-borne diseases?
Solution:
Water-borne diseases can be prevented by drinking clean water. Water should be free from contamination, suspended and dissolved substances. If water is contaminated it should be boiled and filtered before drinking. Periodic cleaning and disinfection of water reservoirs, pools, and tanks should be done.
Question 5.
Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
Solution:
‘A suitable gene’ means the gene which is able to produce antigenic polypeptides of the pathogen in bacteria and yeast. Using recombinant DNA technology, it is possible to produce vaccines in large scale for immunisation. Hepatitis B vaccine is produced using this technology.
Question 6.
Name the primary and secondary lymphoid organs.
Solution:
Primary lymphoid organs are bone marrow and thymus. Secondary lymphoid organs are the spleen, lymph nodes, tonsils, Peyer’s patches of the small intestine, and mucosa-associated lymphoid tissues (MALT).
Question 7.
The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form.
Solution:
Question 8.
Differentiate the following and give examples of each.
Solution:
Question 9.
Draw a well-labeled diagram of an antibody molecule.
Solution:
Question 10.
What are the various routes by which transmission of the human immunodeficiency virus takes place?
Solution:
Various routes of entry of ADDS virus are:
Question 11.
What is the mechanism by which the AIDS virus causes a deficiency of the immune system of the infected person?
Solution:
After getting into the body, the virus enters into the macrophages and converts its RNA genome into DNA with the help of a reverse transcriptase enzyme. The viral DNA takes and directs the infected cells to produce more virus particles i.e., the infected macrophages act like an HIV factory. Simultaneously, the HIV attack the T- lymphocytes and replicate and produce more viruses. Then they are released into the blood and attack other T-lymphocytes.
This will lead to a decrease in the number of T-lymphocytes and the patient begins to show the symptoms such as fever, diarrhea, weight loss etc. Subsequently, his immune system weakens and becomes more prone to infections of bacteria (like Mycobacterium), viruses, fungi and even parasites like Toxoplasma. Finally, he is unable to protect himself.
Question 12.
How is a cancerous cell different from a normal cell?
Solution:
Cancerous cell and normal cell are different in the following aspects:
Question 13.
Explain what is meant by metastasis.
Solution:
The rapid growth of cancerous tumour causes overcrowding and disruption of normal cells. It extends to neighbouring tissues. In the last stage, bits of tumour tissue break off and are carried by the circulating blood or lymphs to other parts of the body, where they invade new tissues and start new tumors called secondary tumors. This property is called metastasis. It is fated due to increasing interference with the body’s life processes.
Question 14.
List the harmful effects caused by alcohol/drug abuse.
Solution:
Harmful effects caused by alcohol/drug abuse are as follows:
Question 15.
Do you think that friends can influence one to take alcohol/drugs? If yes, how can one protect himself/herself from such an influence?
Solution:
Yes. This can be avoided by
Question 16.
Why is it that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
Solution:
Once a person starts taking alcohol or drugs, it is difficult to get rid of this habit because he becomes addicted to it. Addiction is a psychological attachment to certain effects such as euphoria and a temporary feeling of well-being. These drive people to consume drugs/alcohol even when these are not needed, or even when their use becomes self-destructive. With repeated use, the tolerance level of the receptors present in the body increases, which consequently leads to a higher dose of drugs/alcohol and addiction.
Thus, the addictive potential of drugs and alcohol pull the user into a vicious circle leading to their regular use from which he/she may not be able to get out.
Question 17.
In your view what motivates youngsters to take alcohol or drugs and how can this be avoided?
Solution:
There are many factors that motivate youngsters to take alcohol or drug. These include:
This can be avoided by the following measures:
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