Class 8 SELINA Solutions Biology Chapter 8: Diseases and First Aid

(iii) Malaria

(ii) Virus

(iv) Edward Jenner

(iv) Penicillin

(i) Measles

(a) AIDS

(b) Malaria

(c) Malaria

(d) Dengue fever and Chikungunya

(e) Tuberculosis

(a) AIDS: Acquired Immuno Deficiency Syndrome

(b) HIV: Human Immunodeficiency Virus

(c) WBCs: White Blood Cells

(d) BCG: Bacillus Calmette-Guerin

(e) TAB: Typhoid-paratyphoid A and B

(a) Two types of diseases on the basis of whether they can be spread or not:

1.      Communicable or Infectious Diseases

2.      Non-communicable or Non-Infectious Diseases

(b) Four ways of indirect methods by which infectious diseases can spread:

1.      Touching and sharing items used by the infected person

2.      Contaminated food and water or drink

3.      Vectors

4.      Droplets

(c) Three diseases caused by viruses:

1.      Common Cold

2.      Influenza (The Flu)

3.      HIV/AIDS

(d) Three diseases in which germs are carried by mosquitoes:

1.      Malaria

2.      Dengue fever

3.      Chikungunya

(e) Four methods by which vaccines can be prepared:

1.      Using killed germs

2.      Using living weakened germs

3.      Using fully virulent living germs

4.      Using toxoids

(a) Health: Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.

(b) Public hygiene: Public hygiene refers to the science and practice of protecting and improving the health of a community. It involves proper disposal of human excreta and domestic wastes.

(c) Vaccine: A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease.

(d) Toxoids: Toxoids are extracts of toxins secreted by bacteria and these poisons are made harmless by the addition of formalin to retain the capacity to produce antibodies.

(e) First aid: First aid is the immediate care or help given to a patient at the time of medical emergency before he or she is taken to a doctor.

(a) Communicable diseases:

1.      Influenza

2.      Measles

(b) Non-communicable diseases:

1.      Diabetes

2.      Heart attack

(c) Viral diseases:

1.      AIDS

2.      Chickenpox

(d) Bacterial diseases:

1.      Cholera

2.      Typhoid

(e) Vectors:

1.      Mosquitoes

2.      Houseflies

Non communicable or non-infectious diseases are those which are not caused by any germ; therefore these diseases cannot spread from an infected person to a healthy person. Non communicable diseases may be caused due to improper functioning of the body organs. Diabetes, cancer, and heart attack are common non communicable diseases.

Communicable diseases are those diseases which spread from an infected person to a healthy person by the entry of germs called pathogens. Cholera, malaria, and typhoid are common communicable diseases.

We can control the spread of diseases by mosquitoes and houseflies in the following ways:

·         Use mosquito repellants.

·         Throw garbage in covered bins.

·         Avoid stagnation of water.

·         Check breeding of insects.

Public hygiene involves proper disposal of human excreta and domestic wastes. It is equally important as personal hygiene for the following reasons:

·         Sewage should be chemically treated first before being released into the water bodies to avoid water-borne diseases.

·         There should be proper sewer lines connected to sewage treatment plants.

·         A healthy environment should be maintained to prevent the spread of diseases due to breeding of mosquitoes, houseflies, and microorganisms.

·         Garbage should be kept in covered bins to avoid breeding of flies.

·         Water should not be allowed to stagnate outside your house and in the neighbourhood.

·         All drains should be covered to prevent breeding of mosquitoes.

·         Contamination of drinking water with faeces should be prevented as it is a major cause of diseases.

Vaccination is the practice of artificially introducing germs or germ substances into the body for developing resistance to particular diseases. The material introduced into the body is called the vaccine. Usually, the vaccine is introduced into the body by injection and sometimes orally.

A vaccine can be prepared by any one of the following four methods:

1.      Using killed germs — e.g., TAB vaccine for typhoid.

2.      Using living weakened germs — e.g., the vaccine for measles.

3.      Using fully virulent living germs — e.g., the vaccine for smallpox.

4.      Using toxoids — e.g., the vaccines used for diphtheria and tetanus.

First aid for burns depends on the degree of burns.

·         In the case of superficial burns, pour cold water over the burnt area. Then dry that portion and cover with sterile dressing.

·         In the case of deep burns, never use water, and cover the injured part with dressing.

·         In the case of chemical burns, wash with running water for 10 minutes and then cover with dressing.

(a) Disease:

·         Disease is a departure from normal health through structural or functional disorder of the body.

·         There are two major categories of diseases — Communicable or infectious diseases and Non-communicable or non-infectious diseases.

·         Communicable diseases spread from an infected person to a healthy person through pathogens, e.g., cholera, typhoid.

·         Non-communicable diseases do not spread from an infected person to a healthy person, e.g., diabetes, heart attack.

(b) Immunisation:

·         Immunisation is an artificial way of achieving protection from infections by the introduction of dead or weakened germs into one's body.

·         It is a process by which the body of an individual is made resistant to a specific disease by vaccination.

·         In India, immunization programme is under way to immunise infants against tetanus, diphtheria, whooping cough, mumps, measles, tuberculosis, and polio.

(c) Pathogen:

·         Communicable diseases are caused due to microorganisms such as viruses, bacteria, fungi, worms, and protozoa.

·         These disease-causing germs are called pathogens.

·         Pathogens spread from one person to another through air, water, food, physical contact, cuts, sexual contact and from insects like mosquitoes, and flies.

(d) AIDS:

·         AIDS stands for Acquired Immuno Deficiency Syndrome.

·         It is caused by HIV (Human Immunodeficiency Virus).

·         It weakens the immunity or self-defence mechanism of the human body.

·         AIDS makes the infected person prone to many other infectious diseases.

·         It spreads through sexual contact, blood transfusion and infected syringes.

(e) Vaccination:

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

·         The material introduced into the body is called the vaccine.

·         Vaccines can be injected into the body or given orally.

·         When exposed to vaccines, the body makes antibodies which fight against the germs of particular diseases.

(f) Vector:

·         Vectors are organisms such as house flies and mosquitoes which carry germs from a source of infection but themselves do not get the infection.

·         For example, mosquitoes while feeding on the blood of a malaria patient, gain the germs in their bodies, and transfer them into the blood stream of a healthy person whom they bite next.

·         Houseflies carry germs from garbage or sewage and deposit them on food. A person who eats this contaminated food gets the disease.

Clues Across (1-6)

1. Virus

2. Lice

3. BCG

4. Cough

5. Flies

6. AIDS

Clues Down (7-11)

7. Vaccine

8. Jaundice

9. Lung

10. Rabies

11. Mouth