Human Health And Disease Class 12th Biology CBSE Solution

Class 12^th Biology CBSE Solution

Exercises

1. What are the various public health measures, which you would suggest as safeguard against…
2. In which way has the study of biology helped us to control infectious diseases?…
3. Amoebiasis How does the transmission of each of the following diseases take place?…
4. Malaria How does the transmission of each of the following diseases take place?…
5. Ascariasis How does the transmission of each of the following diseases take place?…
6. Pneumonia How does the transmission of each of the following diseases take place?…
7. What measure would you take to prevent water-borne diseases?
8. Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA…
9. Name the primary and secondary lymphoid organs.
10. The following are some well-known abbreviations, which have been used in this chapter.…
11. Innate and acquired immunity Differentiate the following and give examples of each:…
12. Active and passive immunity Differentiate the following and give examples of each:…
13. Draw a well-labelled diagram of an antibody molecule.
14. What are the various routes by which transmission of human immunodeficiency virus takes…
15. What is the mechanism by which the AIDS virus causes deficiency of immune system of the…
16. How is a cancerous cell different from a normal cell?
17. Explain what is meant by metastasis.
18. List the harmful effects caused by alcohol/drug abuse.
19. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one…
20. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of…
21. In your view what motivates youngsters to take to alcohol or drugs and how can this be…

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Exercises

Question 1.

What are the various public health measures, which you would suggest as safeguard against infectious diseases?

Answer:

Common preventive public health measures are:

a) Education : People should be educated about the infectious diseases.

b) Vaccination : People should get vaccination to avoid infection.

c) Sanitation : Proper sanitation can prevent spread of diseases.

d) Isolation : The patient should be separated to avoid infection to others.

e) Sterilization : Patient's belongings should be sterilized.

f) Eradication of vectors : The breeding places of the vectors should be destroyed and adult vectors killed by suitable methods.

Question 2.

In which way has the study of biology helped us to control infectious diseases?

Answer:

The study of biology has helped us to control infectious diseases in the following ways :

a) The use of vaccines & immunization programme is due to advancements in biology.

b) Biotechnology is helping to make new and safe vaccines.

c) Discovery of antibodies and various other drugs have also enabled to treat infectious diseases.

Question 3.

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

Amoebiasis

Answer:

Amoebiasis - Faecal or oral route

Explanation: Amoebiasis is also called Amoebic dysentery. It is caused by Entamoeba histolytica. It is transmitted through faecal or oral route or sexual transmission.

Question 4.

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

Malaria

Answer:

Malaria - By the bite of female Anopheles mosquito.

Explanation: Plasmodium is the malarial parasite. Its sexual phase occurs in the female Anopheles mosquito which is its primary host. The asexual phase occurs in humans which is its secondary host. The patient displays symptoms of malarial fever after a period of 14 days from infectious bite. Body temperature may reach 106°F at the height of fever. The patient sweats a lot & the next attack takes place after 48 hours. Quinine is the oldest drug for malaria.

Question 5.

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

Ascariasis

Answer:

Ascariasis - Through contaminated food and water.

Explanation:Ascariasis is caused by Ascaris lumbricoides. A large number of adult Ascaris worms infest a single host, they obstruct the intestinal passage and cause abdominal discomfort like colic pains. The patient may suffer from indigestion, diarrhoea and vomiting. The disease can be treated by administering antihelminthic drugs like oil of chenopodium, Alcopar, Bendex, Dewormis, Zental etc.

Question 6.

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

Pneumonia

Answer:

Pneumonia - From the sputum of the patient.

Explanation: Pneumonia is caused by Streptococcus pneumoniae & Haemophilus influenzae. It is a serious disease of the lungs. Lymph and mucus collect in the alveoli and bronchioles of the lungs so lungs do not get sufficient air. No such vaccine is available. However, Penicillin, Streptomycin and Ampicillin is used.

Question 7.

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

Answer:

The following measures could ne taken to prevent waterborne diseases:

a) Fresh and clean water should be taken.

b) If water is contaminated it should be filtered before drinking.

c) Water resources should be disinfected.One should not take pond's water.

Question 8.

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

Answer:

The term 'suitable gene' refers to that gene (specific segment of DNA) that will be modified in the host to produce specific protein to kill specific disease causing organisms.

Question 9.

Name the primary and secondary lymphoid organs.

Answer:

The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen sensitive lymphocytes.

Bone marrow : Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are formed. Maturation of B-lymphocyte occurs here.

Thymus : Thymus is the site for T-lymphocytes maturation. Thymus is situated near the heart.

The secondary lymphoid organs are spleen, lymph nodes, tonsils,Payer's patches of small intestine and appendix.

Spleen : It is a bean-shaped organ which is the largest single mass of lymphoid tissue in the body. In foetus the spleen produces all type of blood cells but in adult it only produces lymphocytes.

Lymph nodes : These are small solid structures found at intervals along the lymphatic system. They are composed of lymphoid tissue and act as filters for the lymph. Lymph nodes also produce lymphocytes and plasma cells.

Tonsils : Usually there are only 6 tonsils. They act as filters to protect the body from bacteria and aid in the formation of white blood cells.

Peter's patches : They are clusters of lymph nodules found in small intestine along the ileum. They produce lymphocytes.

Mucosal-Associated Lymphoid Tissue (MALT) : MALT are significant aggregation of lymphoid tissues which are seen in relation to the mucosa of the major tracts like respiratory, alimentary canal and urinogenital tracts. It constitute about 50% of the lymphoid tissue in human body. They don't serve as filters of lymph. They are centres of lymphocytes production. Phagocytic macrophages and dendritic cells are also present.

Question 10.

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

Answer:

(a) MALT : Mucosal-associated lymphoid tissue.

Explanation: MALT is a significant aggregation of lymphoid tissue which are seen in relation to the mucosa of major tracts, like alimentary canal, respiratory tract etc. They are centres of lymphocytes production.

(b) CMI : Cell-mediated Immunity

Explanation: CMI consists of T-lymphocytes which produce 4 types of T cells. It defends the body against all pathogens including fungi and protozoa. It reacts against transplants. It provides immunity against cancer.

(c) AIDS : Acquired Immuno Deficiency Syndrome

Explanation: AIDS is a disorder of cell mediated immune system of the body. There is a reduction in the number of helper T cells which stimulate antibody production by B-cells. AIDS is caused by HIV(Human Immunodeficiency virus). AIDS was first noticed in USA amongst homosexuals in 1981.

(d) NACO : National AIDS Control Organisation

Explanation: NACO educate people about AIDS.They make people aware of the various ways and precautions to be taken to avoid the chances of AIDS.

(e) HIV : Human Immunodeficiency Virus

Explanation: HIV is a retrovirus that attacks helper T-cells. The HIV virus is spherical in shape. It consists of a single stranded RNA filament segmented into identical filaments and is associated with a reverse transcriptase enzyme.

Question 11.

Differentiate the following and give examples of each:

Innate and acquired immunity

Answer:

Question 12.

Differentiate the following and give examples of each:

Active and passive immunity

Answer:

Question 13.

Draw a well-labelled diagram of an antibody molecule.

Answer:

Antibodies are immunoglobulins(Igs) which are produced in the body in response to antigen or foreign bodies. Antibodies are produced by B lymphocytes and plasma cells. An antibody molecule consists of the following parts :

a) Heavy and light chains : An antibody molecule is made up of 4 peptide chains, two small called light chains and two longer called heavy chains. Antibody is thus represented as H2L2. The heavy chains have larger number of aminoacids while light chains have less aminoacids.

b) Constant and Variable regions : There are two different regions the constant and the variable region in each chain of the antibody.

c) Disulphide Bonds and Hinge region : A disulphide bond joins a light chain with a heavy chain. Two disulphide bond also link the two heavy chains. This part of the antibody displays considerable flexibility and is called hinge region.

Question 14.

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

Answer:

The various routes by which transmission of human immunodeficiency virus takes place are :

Virus of AIDS is transmitted via blood and semen.

a) Sexual contact with infected person.

b) Transfusion of contaminated blood and blood products.

c) By sharing infected needles & syringes in case of intravenous drug abusers.

d) From mother to child through placenta.

e)Use of contaminated razors.

f) Use of contaminated needles for boring pinnae.

g) Sexual intercourse with an infected partner without a condom.

h) Artificial insemination.

I) Organ transplant.

Question 15.

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

Answer:

In infected person, HIV enters into macrophages where virus is replicated and gets incorporated with host cell's DNA with the help of enzyme RNA transcriptase. Infected host cells produce virus particles so that host's macrophages act as HIV factors. At the same time, HIV enters into helper T-lymphocytes and replicates to form progeny virus. They again attack blood and helper T-lymphocytes . This disease in T-helper leads to deficient immunity in infected persons.

Question 16.

How is a cancerous cell different from a normal cell?

Answer:

Question 17.

Explain what is meant by metastasis.

Answer:

A phenomenon in which cancer cells spread to distant sites through the body fluids to develop secondary tumor is called metastatis.

Question 18.

List the harmful effects caused by alcohol/drug abuse.

Answer:

The effects of alcohol abuse are :

a) Deficiency of nutrients - Deficiency of nutrients such as minerals, proteins and vitamins are found in alcoholics. Low blood potassium, magnesium, calcium, zinc and phosphorus can occur in alcoholics.Vitamins like thiamine (B1), nicotinic acid(B3), pyridoxine(B6), folic acid, ascorbic acid(vitamin C) and vitamin A may be deficient in alcoholics. Thiamine (B1) deficiency causes Wernicke's and Korsakoff's syndrome.

b) Effects on brain - Alcohol is depressant to the brain. Alcohol decreases sleep and depresses rapid eye movement(REM). Cerebrum is affected first followed by cerebellum.

c) Mallory Weiss Syndrome - Dilute alcohol stimulates gastric secretion. Acute alcoholic intake can result in inflammation of the oesophagus and stomach.

d) Diseases of liver - Absorbed alcohol is carried directly to the liver, where it becomes the preferred fuel. There is destruction of hepatocytes and fibroblasts.The liver shrinks in size.

e) Increased cancer risk - Alcoholics have a rate of carcinoma 10 times higher than that expected in the general population.

f) Effect on kidneys - Diuresis is noticed after alcohol intake. Alcohol induced inhibiton of ADH secretion. Deficiency of ADH cause more urine output.

g) Impotency and Infertility - Chronic alcoholic men may show testicular atrophy with shrinkage of the seminiferous tubules and loss of sperm cells. Chronic alcoholism can produce impotence and infertility.

h) Foetal Alcohol Syndrome (FAS) - Heavy drinking during pregnancy results in the foetal alcohol syndrome which includes facial changes and mental retardation.

The effects of drug abuse are :

a) Nervousness and Psychosis - Prolonged use of drugs leads to nervousness and psychosis. Drug addicts neglect their studies, duty and bring frustration not only for themselves but also for their family and community.

b) AIDS and Hepatitis - Many drug addicts inject these drugs in their blood vessels with previously used needles. AIDS and Hepatitis-B are common in addicts using intravenous drugs.

c) Impotency, Chromosomal Aberration and production of Abnormal babies - Continuous use of narcotics and stimulants cause impotency and chromosomal aberration and production of abnormal babies.

d) Hormonal changes - Hormonal changes include an increase in cortisol levels, inhibition of vasopressin, reversible decrease in serum thyroxine and a more marked decrease in serum tripod other on one(T3).

e) Effects on kidneys - Functions of kidney of drug abused persons are impaired or maybe damaged.

Question 19.

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

Answer:

Yes, friends can influence for taking alcohol or drugs. Following measures can be taken :

a) Avoiding undue peer pressure.

b) Not taking undue pressure of failures beyond its threshold.

c) Getting counselling from some counsellor.

d) Seeking help from parents and peers.

e) Seeking medical help.

Question 20.

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.

Answer:

Once a person starts taking alcohol or drugs, he becomes addict to these substances physically and mentally. Whenever he tries to get rid of this habit, he shows unpleasant withdrawal symptoms and these include vomiting, diarrhoea, shivering, twitching, perspiration, abdominal and muscular cramps.

So, it becomes difficult for a person to get rid of this habit.

Question 21.

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

Answer:

Youngsters generally take alcohol or drugs on the basis of following factors :

a) Curiosity

b) Pleasure

c) To escape from the realities of life, to overcome frustration and depression.

d) Friends pressure

e) Desire of excitement

f) Desire to do more work

g) Unhappy married life

h) Monotony of daily life

It can be avoided by the following ways :

a) Educating and counselling the child to face problems and stresses and accept disappointments and failure as a part of life.

b) A child should not be pushed unduly to perform beyond his capacity.

c) Parents and teachers should be alert about the activities to the child.

d) Help can be taken from highly qualified psychologists and psychiatrists.