Biology 12 Human Health and Disease Chapter 8 – Exercise

Q 1. What are the various health measures which you would suggest to safeguard us against infectious diseases?

Ans 1. Preventive measures are precautionary steps taken to check the transmission of infectious diseases. Common preventive measures include education, isolation, vaccination, sanitation, and sterilization.

  1. Education: People should be educated about the communicable diseases so that they may protect themselves against infection.
  2. Isolation: a person suffering from an infectious disease should be segregated so that other do not catch infection from him.
  3. Vaccination: people should get vaccination to avoid infection, perticularly, during epidemic. Vaccination is available against cholera, typhoid, tuberculosis and many other diseases.
  4. Sanitation: Garbage heaps, polluted water, foods exposed to dust and flies are the chief sources of disease-causing organisms. Sanitary surroundings can prevent spread of diseases.
  5. Sterilization: Patient’s surroundings and articles of use should be sterilized. Soap, phenyl, Dettol, and antiseptic lotion may be used parts of the country.

Q 2. How does transmission of each of the following diseases take place?

(a) Amoebiasis (b) Malaria      (c) Ascariasis  (d)

Ans 2. (a) Amoebiasis: is caused by Entamoeba histolytica. Infection occurs by ingesting cysts with food and drinks. These cysts are carried by flies from faeces to food and drinks.

  • Malaria: Malaria is caused by Plasmodium sp. Malarial parasites are carried from the infected to the healthy persons by the female anopheles mosquito. The mosquito picks up the parasites along with the blood when it bites an infected person. When this mosquito bites healthy person, parasites migrates into his blood with saliva. Which the mosquito injects before sucking up blood to prevent its clotting.
  • Ascariasis: Man gets infection by taking Ascaris eggs with food and water. Children become infected by ingesting soil.
  • Pneumonia: it spreads by sputum of the patient. Pneumococci are inhaled and get lodged in the bronchioles.
Q 3. What measure would you take to prevent water-borne diseases?
Ans. Water borne diseases can be prevented by using clean drinking water and also periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks.

Q 4. Name the primary and secondary lymphoid organs.

Ans 4. (a) Primary lymphoid organs are bone marrow and thymus.

(b) Secondary lymphoid organs are spleen, lymph nodes, tonsils, peyer’s patches of small intestine and appendix.

Q 5. The following are some well-known abbreviations which have been used in this chapter. Expand each one of its full from.

  1. MALT
  2. CMI
  3. AIDS
  4. NACO
  5. HIV

Ans 5.  MALT – Mucosal Associated Lymphoid Tissues

CMI – Computerized Magnetic Imaging.

AIDS – Acquired Immunodeficiency Syndrome.

NACO – National Aids Control Organization.

HIV – Human Immunodeficiency Virus.

Q 6. Differentiate between following and give examples of each:

  1. innate and acquired immunity
  2. active and passive immunity

Ans 6.

  1. Innate or Inborn immunity: certain animals do not suffer from some infectious diseases. The reason is that the microbes that cause these diseases fail to flourish in such animals. This type of immunity is inherited by the organism from the parents and protects it from birth throughout life. It is known as innate or inborn immunity.

For example: human beings have innate immunity against distemper, a fatal diseases of dogs.

Acquire or adaptive Immunity: This is the immunity developed by an animal in response to a disease caused by infection of microbes. It is specific and is mediated by antibodies or lymphoid cells or both which make the antigens inactive or harmless. It not only relieves the victim of the infectious disease but also prevents its further attack in future. The acquired immunity lasts for the whole life of the animal in case of certain diseases and for a few years in case of other diseases. Such diseases have already been mentioned. The memory cells formed by B- and T-cells are the basis of acquired immunity. They have long lives and provide antibodies and killer T-cells in subsequent infections.


Active Immunity Passive Immunity
1.     immunity is said to be active when person’s own cells produce antibodies in response to infection or vaccination.

2.     It takes time in the formation or antibodies.

3.     It is harmless.

4.     It is long lasting.

1.     Immunity is said to be passive when antibodies produced in other organisms are injected into a person to counteract antigen such as snake venom.

2.     It provides immediate relief.

3.     It may create problems. Foreign antibodies may cause reaction and body may destroy them by forming its own antibodies.

4.     It is not long lasting.

Q 7. Draw a well-labelled diagram of an antibody molecule.


biology antibody molecular

Q 8. What are the various routs by which transmission of human immunodeficiency virus takes place?

Ans 8. AIDS is transmitted only by a contact of infected cells containing blood of a patient which the blood of a healthy person as in

  • unprotected (without condom) sexual intercourse with the infected partner if there is tissue injury to permit blood contact.
  • Use of contaminated needles and syringes to inject drugs or vaccines.
  • Use of contaminated razors for sharing.
  • Use of contaminated needles for bring pinnae.
  • Transfusion of infected blood or blood products.
  • Organ transplant.
  • Artificial insemination.
  • Parturition from mother to body due to rupturing of blood vessels.

Ans 9. What is the mechanism by which the aids virus causes deficiency of immune system of the infected person?

Ans. (i) After getting into the body of the person, the HIV enters into macrophages where RNA genome of the virus replicates to from DNA with the help of reverse transcription enzyme. The viral DNA then gets incorporated into host cell’s DNA to direct the syntheses of virus particles.

(ii) HIV also enters into helper T-lymphocytes. It replicates and produces viral progeny. These viruses are then released into the blood and attack other helper T-lymphocytes. In this way, there occurs progressive decrease in number of helper T-lymphocytes in the body of the infected person. Due to decrease in helper T-lymphocytes, person starts suffering from infections.

Q 10. How is a cancerous cell (neoplastic cell) different from normal cell?

Ans 10. Cancer cell are different from normal cells as they

    1. Continue dividing ceaselessly.
    2. Divide in an uncontrolled manner.
    3. Do not undergo differentiation.
    4. From an ever-growing tumour by accumulation.
    5. Do not remain confined to the part of the body where they are formed.
    6. Invade the neighboring tissue and dislocate their functions.
    7. Spead throughout the body, forming secondary tumours.

Q 11. Explain what is meant by metastasis.

Ans 11. Malignant tumours are a mass of proliferating cells called neoplastic cells. They grow rapidly and invade and damage the surrounding normal tissue. As the tumour cells divide actively and grow, they even starve the normal cells by competing for necessary nutrients. Cells get sloughed from such tumours and migrate to distant sites through blood. At new places of establishment, they start a new tumour. This property is called metastasis.

Q 12. Enlist the various harmful effects which alcohol/drug abuse may have.

Ans 12. List of various harmful effects of alcohols and drugs.

List of harmful effects of alcohols.

  1. Effect on Nervous system.
  2. Effect on Stomach
  3. Effect on Liver
  4. Effect on Heart
  5. Effect on Kidneys
  6. Effect on Immunity
  7. Effect on babies.
  8. Effect on Society
  9. Effect on the Famil

Effects of drug abuse.

  1. Lesion tension and anxiety without sedation and inducing sleep.
  2. Depress CNS3 activity, give feeling of calmness, relaxation, drowsiness. High doses induce deep sleep.
  3. Suppress brain activity, relieve pain, stimulate nervous system.
  4. Make a person more wakeful, alert and active, cause excitement.
  5. Alter thoughts, feeling and perceptions. Cause illusions.
Q 13. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

Ans 13. Yes, friends can influence person to take alcohol/drugs. One can protect himself/herself from such an influence by avoiding experimental use of alcohol/drug for curiosity or pleasure and avoiding the company of such friends.

Q 14. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of habit? Discuss it with your teacher.

Ans 14. It is really difficult to get rid of the habit of taking alcohols or drugs. Because, s/he take alcohol because of social pressure, desire for excitement, feeling or independence, liking or taste, desire to escape from such realities of life as disappointments and failures, and desire to offset the hardships and monotony of daily life and when they come out of that problems they don’t know they are habitual of alcohols or drugs, and addiction to alcohol is called alcoholism. It could be the reason, that it is difficult to get rid of it.

Q 15. In your views, what motivates the youngsters to take of alcohol or drugs and how can this be avoided?

Ans 15. In my views, curiosity, friend’s pressure, frustration and depression, desire for more work, looking for a different world, relief from pain, family history, excitement and adventure and ability of drugs motivates the youngsters to take of alcohol or drugs.

It can be avoided when, the physicians should prescribe the habituating drug only to the genuine persons and only for the essential duration. Pharmacists should not sell these drugs without the physician’s prescription. These steps can restrict drug abuse.

Some people make pain an excuse to get drug prescription from a physician. The person who continue to have pain should be offered an alternative for the control of the pain so that they may give up the use of the drug. They may be advised to put up with a certain amount of discomfort in order to avoid drug independence.

The parents should keep a watch on the children and should check them from using drug as soon as they find signs of addiction in them.

Social workers and policemen, if they find a drug abuser, should inform the parents or deaddiction centers.

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