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Class 9 SELINA Solutions Biology Chapter 17 - Aids To Health

Aids To Health Exercise Ex. 1

Solution A.1(a)

(iii) an antibiotic

Solution A.1(b)

(i) Innate immunity

Solution A.1(c)

(iv) previous infection with a disease-causing organism

Solution A.1(d)

(ii) Diphtheria, Pertussis and Tetanus 

Solution A.1(e)

(ii) An extract of dead and weakened microbes 

Solution A.1(f)

(iv) Bacillus 

Solution A.1(g)

(ii) Immunity

Solution A.1(h)

(iv) Mucus

Solution A.1(i)

(i) Blood

Solution A.1(j)

(iii) Antigens

Solution B.1

(a) Salvarsan

(b) Penicillin

(c) Artificially acquired passive immunity

(d) Pentidsulph

(e) Alexander Fleming

Solution B.2

(a) AIDS: Acquired Immuno Deficiency Syndrome

(b) BCG: Bacillus of Calmette Guerin

(c) DPT: Diphtheria, Pertussis and Tetanus

(d) DDT: Dichlorodiphenyl trichloro ethane

(e) WHO: World Health Organisation

(f) HIV: Human Immunodeficiency Virus

(g) STD: Sexually Transmitted Disease

(h) WBC: White Blood Cell

(i) TAB: Typhoid-Paratyphoid A and B

(j) COVID-19: Corona virus disease-19

Solution B.3

(a) Carbolic acid, Iodine, Benzoic acid, Boric acid and Mercurochrome

(b) Cresol, Phenol, Lysol, Lime and DDT

(c) Penicillin and Streptomycin

(d) Sulphadiazine and Sulphanilamide

(e) Syphilis and Gonorrhea

Solution C.1

(a) Immunity is the capacity of our body to fight with foreign substances such as bacteria, viruses and toxins that enter our body and render them harmless.

(b) Antibodies are special chemicals found in the blood which act against the germs or their secretions.

(c) Prophylaxis is the practice of artificially introducing the germs or the germ substance into the body for developing resistance to particular diseases.

(d) Vaccine is a biological preparation of a weakened or killed pathogen (disease-causing microbe) which stimulates the formation of antibodies and develops immunity against a particular disease.

(e) Immunisation is the process of developing resistance to disease-producing germs or their toxins by introducing killed germs or germ substances to induce the production of specific antibodies.

Solution C.2

(a) Lysol is an antiseptic/disinfectant. (Penicillin is an antibiotic)

(b) The treatment of diseases by the use of chemical substances is known as chemotherapy.

(c) WBCs are germ-fighting cells of our body.

(d) Antibodies are the proteins that belong to the class of immunoglobulins.

(e) Polio drops are given to small babies orally.

Solution C.3



The Nature of Vaccine 


1. Typhoid

2. Killed germs

Salk's vaccine

3. Poliomyelitis

4. Killed germs


5. Tuberculosis

Living weakened germs

Vaccines for measles


6. Living weakened germs

Cowpox virus

7. Small pox

8. Living fully poisonous germs



9. Diphtheria and

10. Tetanus

Inactivated toxins secreted by bacteria


Solution C.4

(1) Innate immunity

(2) Acquired immunity

(3) Specific immunity

(4) Active acquired immunity

(5) Passive acquired immunity

(6) Natural acquired active immunity

(7) Artificial acquired active immunity

(8) Natural acquired passive immunity

(9) Artificial acquired passive immunity

Solution C.5

(a) Formalin (Rest are antiseptics)

(b) Mercurochrome (Rest are disinfectants)

(c) ATP (Rest are vaccines) 

(d) Skin (Rest are germ-killing secretions)

(e) Streptomyces (Rest are antibiotics)

Solution C.6

1.  Antibiotics have a wide use in medicine to fight infections.

2.  Certain antibiotics are used as food preservatives, especially for fresh meat and fish.

3.  Some antibiotics are used in treating animal feed to prevent internal infection.

4.  Some antibiotics are used for controlling plant pathogens.

Solution C.7

Merits of local defence systems:

1.  Local defence systems start working instantaneously.

2.  These systems are not dependent on previous exposure to infections.

3.  They are effective against a wide range of potentially infectious agents.

Solution D.1

(a) Antiseptic is a mild chemical substance which is applied to the body to kill germs, whereas an antibiotic is a chemical substance produced by a microorganism which can kill or inhibit the growth of some other disease-producing microorganisms.

(b) Antiseptic is a mild chemical substance which is applied to the body to kill germs, whereas a disinfectant is a strong chemical applied to spots or places on the body where germs thrive and multiply.

(c) Disinfectant is a strong chemical applied to spots or places on the body where germs thrive and multiply, whereas deodorants are neither antiseptics nor disinfectants; they are aerosols used to mask a bad smell.

(d) Vaccination is the introduction of any kind of dead or weakened germs into the body of a living being to develop immunity (resistance) against a disease, whereas sterilisation is a process of eliminating or killing all the microbes present on a surface, contained in a fluid, in medication or in a compound such as biological culture media.

(e) Active immunity is the immunity developed by an individual due to a previous infection or antigen which enters the body naturally, whereas passive immunity is the immunity provided to an individual from an outside source in the form of 'readymade' antibodies.

(f) Innate immunity is the immunity by the virtue of genetic constitutional makeup, i.e. it is inherited from parents. It is present in the body without any external stimulation or a previous infection, whereas acquired immunity is the resistance to a disease which an individual acquires during a lifetime. It may be the result of either a previous infection or from readymade antibodies supplied from outside.

Solution D.2

  Vaccination is the practice of artificially introducing germs or the germ substance into the body for developing resistance to particular diseases.

  Scientifically, this practice is called prophylaxis and the material introduced into the body is called the vaccine.

  The vaccine or germ substance is introduced into the body usually by injection and sometimes orally (e.g. polio drops).

  Inside the body, the vaccine stimulates lymphocytes to produce antibodies against the germs for that particular disease.

  Antibodies are an integral part of our immunity. Their function is to destroy the unwanted particles which enter the body.

  Vaccines give our immunity a signal to produce specific antibodies. Hence, the principle of vaccination is to produce immunity against a disease.

Solution D.3

Whenever a germ or infection invades the body, a signal is sent to the immune system to produce specific antibodies. To cope with the number of germs being multiplied inside the body, white blood cells start multiplying rapidly. This enables them to produce more number of antibodies and stop the infection in time. So, abnormally large numbers of WBCs in the blood are usually an indication of some infection in our body.

Solution D.4

(a) Antiseptics:

Antiseptics are mild chemical substances applied to the body which prevent the growth of some bacteria and destroy others.  

Examples: Lysol and iodine


(b) Disinfectants:

Disinfectants are chemicals which kill microorganisms they come in contact with. Disinfectants are usually too strong to be used on the body.

Examples: Cresol and phenol


(c) Vaccines: 

Vaccines are materials administered in the body to provide passive immunity. The materials are generally germs or substances secreted by germs.

Examples: OPV (oral polio vaccine) and DTP (diphtheria, tetanus and pertussis)

Solution D.5

Diphtheria is a serious bacterial infectious disease. It leads to cold, coughing, sneezing and, in severe cases if undiagnosed, it might result in heart failure or paralysis.

Treatment includes a combination of medications and supportive care. The most important step is prompt intravenous administration of diphtheria toxoid which is made harmless. The harmless toxoid once administered in a patient's body triggers the production of antibodies against the pathogens causing diphtheria.

Solution D.6

It is important to know how the germs leave the body of a patient as there are some diseases and infections which are transmitted through air, water or just by direct contact. Therefore, to take precautions and protect others from further infections, it is a must to know how the germs leave the body of an infected person.

Solution E.1

(a) Figure A shows the process of diapedesis. Diapedesis is the process by which white blood cells get squeezed out of the wall of the blood capillaries into the surrounding environment in the event of an injury.

(b) The blood vessels shown in figure A are capillaries. Capillaries have thin walls. Oxygen and nutrients from the blood can move through the capillary walls and enter inside the organs and tissues. The capillaries also transport waste products away from the tissues.

(c) Figure-B shows the process of phagocytosis. Phagocytosis is the process by which white blood cells surround and engulf the bacteria or the germs and destroy them.

(d) White blood cells (WBCs) are shown in the given figures. The technical name of white blood cells is phagocytes.

(e) The specific type of cell containing 4 lobed nucleus of the phagocyte is called a neutrophil.

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