BIOLOGY [5 Mark Question Answer]

It is a viral disease caused by the virus called HIV ( Human immunodeficiency virus) This virus makes the defence mechanism of the human body very weak. The immune system in the body as W.B.C. becomes weak. Thus the person catches the infectious diseases very easily. This disease spreads through sexual contact as one of the partners may be a carrier of the disease. It may spread through the blood transfusion and infected syringes, blades of the barbers, it may infect the developing baby through the blood by the 1087 mother. It is a very deadly disease.

Allergy is an unpredictable reaction to a particular substance. This type of substance is called an allergen. Different people are allergic to different substances. A few common allergens are dust, spores, pollen, certain clothes, particular cosmetics, etc. The common areas of the body parts which are affected by allergies are skin, respiratory and digestive tracts. Asthma, eczema, diarrhea, vomiting, nausea, etc. are some of the common allergic reactions.

It means we make the body immune to certain diseases by introducing respective weakened germs into the body. Thus we develop resistance to the concerned disease this process is called immunisation. The germs or the material introduced into the body to make it resistant to the concerned disease is called a vaccine. This produces antibodies in the body of the person and the person can be saved by these antibodies. The vaccine can be given by the injection or orally as polio drops, tap vaccine for typhoid, BCG vaccine for tuberculosis.

Preparation:

1. Killed germs are introduced into the body These act as a vaccine for TAB, the vaccine for typhoid, Salk’s vaccine for poliomyelitis. Rabies vaccine for a dog bite.
2. Living weakened germs: The living germs are treated in such a way that they become very weak and as such, they cannot cause the disease. They can induce antibody formation such as the vaccine for measles and the frozen dried BCG vaccine for tuberculosis.
3. Living fully virulent germs: These virulent germs in small doses are introduced into the body as vaccine and these ArunDeep’s M-S-Biology-7 109
   produce antibodies in the body and these do not allow the germs of a particular type to cause that disease. In this vaccination, the person is inoculated with cowpox virus. It is very similar to the smallpox virus.
4. Toxoids: Toxoids are prepared from the extracts of toxins secreted by bacteria. These toxins are poisons and these are made harmless by adding formalin into them. They retain their capacity and as a result, when introduced into the body they produce antibodies into the body and do not allow the germs to grow in the body as vaccines for diphtheria and tetanus.

For developing resistance in the body we introduce germs or germ substances in the body to develop resistance in the body against a particular disease. The material introduced into the body is called vaccine, this practice is called prophylaxis.
The germ or the germ substance is put into the body orally as polio drops or it is introduced by injection as TAB vaccine. Vaccine or vaccination was attached with small pox, but it is now used in a general sense.