Why do we fall ill of Class 9


Food is the basic necessary of life. There are various components of food such as carbohydrates, fats, proteins, vitamins and minerals. These components called nutrients, perform important functions in the body.  Nutrition is closely linked to health, Each of these components of food has specific function in the body. These food components are required in specific amounts. Good dietary habits lead to sound health and good mental development.


According to World Health Organisation (WHO), (1947), health is defined as –“Health is a state of complete physical, mental and social well-being, and not merely an absence of disease or infirmity. Health is a state of body when all the organs and systems are functionally properly and a perfect balance is maintained between the environment and the body.” A person is said to be healthy if one:

  • Has no symptoms of disease and anxiety.
  • Has no physical deformity.
  • Has no mental problems and social tensions.
  • Has no psychological tensions.
  • Has all the body organs functioning properly.
  • Has purposeful life.
  • Has sufficient balanced diet.

Germ theory of disease

In ancient time man believed that bad spirits present inside the body of the victim caused ill-health. People also believed in the supernatural theory of disease. Chicken pox, small pox, cholera were thought to be inflicted as a curse of some angry goddess. Malaria is thought to be caused by inhalation of bad air as miasmatic theory proposed that diseases are caused due to noxious air and vapours.

Louis Pasteur (1822-1895), the French bacteriologist, demonstrated the presence of bacteria in air Microscope was invented in 1835 and upto 1860 different type of micro organisms were detected.
In 1877, Robert Koch (1843-1910) showed that anthrax was caused by a bacterium. The discoveries of Pasteur and Koch confirmed that microbes were responsible for causing disease, and this came to be known as the germ theory of disease.

Significance of Health:The important characteristics of a person having good health are:

  • Free from sickness and diseases.
  • Free from unnecessary anxiety.
  • Free from social and psychological tensions.
  • Self-confidence.
  • Feeling of joy in living.
  • Ability to work efficiently and at his best.

Community Health:

Community health has been defined as including “All the personal health along with the environmental services in a human community.”Some of the services which need to be developed and provided at the community level are described below:

  • Establishment of health care services like primary health centres, district hospitals, community health centres, medical college hospitals, All India Institutes, Regional Hospitals, specialized hospitals and other Apex Institutions.
  • Proper disposal of sewage and garbage.
  • Prevention of breeding sites of harmful insects.
  • Prevention and control of environmental pollution (by Central and State Pollution Control Boards).
  • Provision of safe drinking water.
  • Prevention and control of diseases (like tetanus, measles, hepatitis, tuberculosis, diphtheria, whooping cough) through vaccination, medical services and medicines.
  • Providing community education on nutrition and health.
  • Providing health education to school children.
  • Providing medical care to school children.
  • Providing family welfare education and services, and maternal and child health services.
  • Prevention of food adulteration.

Difference Between Personal Health and Community Health :

Personal Health

Community Health

  • The state of physical, mental and social well
  • It is maintenance, protection and improvement of health of the whole
  • Only the individual maintains his/her health.
  • Community.
  • The whole community remains
  • An individual can maintain his health by.
  • Eating balanced diet.
  • Observing personal and domestic hygiene.
  • Consuming clean food, clean water and clean air.
  • Proper exercise, relaxation and good habits.
  • Healthy.
  • Community health can be achieved by.
  • Provision for treated and safe drinking water.
  • Proper disposal of sewage and wastes.
  • Providing medical facilities.
  • Control of communicable diseases.
  • Health education.


NCERT solutions for class 9 Science prepared by Physics Wallah will help you to solve your NCERT text book exercise. NCERT solutions for class 9 Science prepared by Physics Wallah will help you to solve your NCERT text book exercise. 
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