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Why do we fall ill CBSE Class 9

Why do we fall ill

Health and its Failure

The condition of body to function physically, socially and mentally well is termed its health. Health can be defined as a state of physical, mental and social well-being of any individual.

The significance of Health

Health is a state of complete physical, mental and social well being. In order to maintain healthy life cycle, person need to have a balanced diet, regular exercise, lives in proper shelter, takes enough sleep, have good hygiene.

  1. The health of any organism will depend on their surrounding or their environment. Our social environment plays an important role in an individual's health.
  2. Public cleanliness is also important for individual health . Government has to ensure garbage is collected and disposed, of clearing the drains, removing the heap of garbage and thrash littered here and there, close the open-drain water lying stagnant around.

Personal and community issues both matter for health

  • Everybody needs food for good health and food will to earn by doing work. For this, opportunity to do work has to be available for all. Good economic condition and jobs are therefore needed for individual health.
  • Everybody has to be happy in order remain truly healthy. If we mistreat each other and are afraid of each other, we can't be healthy or happy. Social equality and harmony are important for individual health.
  • Distinctions between health and disease-free

    Disease and Its Causes

    1. Lack of nutritious and sufficient food.
    2. Unhealthy and dirty surroundings.
    3. Contact with an infected person.
    4. Use the personal belongings of an infected person.
    5. Drinking untreated water or contaminated water.
    6. Eatingfood from an unclean and unhygienic place.
    7. Lack of hygienic practices.

    What does disease look like?


  • Disease means any abnormality in the structure or function of any organ or body part.
  • It may be due to viruses, bacteria, as well as a lack of a nutritious/balanced diet and public health services.
  • Symptoms of the disease:

  • Symptoms is the basis of diagnose the disease. Headache, fever, and vomiting are all frequent illness symptoms.
  • Pale skin can be used to check for jaundice. Loose motions can be used to check for diarrhea.
  • Acute and Chronic diseases

    The diseases that last for only for a short period of time are called acute diseases.
    For example, cough, cold, fever, etc.

    The diseases that last for a longer period of time or even lifetime are called chronic diseases.
    For example, elephantiasis, cholesterol, cancer, emphysema bronchitis.

    Infectious and non ifectious diseases

    The diseases caused by microbes (pythogen) such as bacteria, virus, fungi, etc. are called infectious diseases. Because it spreads from one infected person to another person.
    Infectious diseases are also called communicable diseases.
    For example, dengue, fever, cold,chicken pox, AIDS, are caused by virus.

    The diseases that are caused by other than microbes are called non-infectious diseases. It can not spreads from one infected person to another person.
    For example, heart disease, stroke,cancer, diabates, chronic lung disease, etc.

    Infectious Diseases

    The diseases caused by microbes (pythogen) such as bacteria, virus, fungi, etc. are called infectious diseases. Because it spreads from one infected person to another person.
    Infectious diseases are also called communicable diseases.
    For example, dengue, fever, cold,chicken pox, AIDS, are caused by virus.

    Infectious Agents

    Infectious agents are the organisms which are capable of producing infection or infectious disease. They are bacteria, fungi, viruses, and parasites etc.

    Means of Spread

    The modes of transmission of disease are:-

    • By air
    • By direct contact
    • By indirect contact
    • By organisms (Mosquito, Flies, Dogs, Rats etc)
    • By food
    Type of Disease Example
    Air born Diseases Common cold, influenza, measles, tuberculosis
    Water born diseases Cholera, typhoid, hepatitis
    Sexual Diseases AIDS, Syphilis
    Animal born Disease Rabbis

    Organ-Specific and Tissue-specific manifestations

    When micro organisms/pythogens affect the entire organ, such as lungs or kidneys, it is known as organ-specific manifestation. When the entire tissue is affected by the micro organisms/pythogens, it is called a tissue-specific manifestation.

    Principles of treatment

    The two ways to treat diseases are:-

    • To reduce the effects of diseases: take medicines to reduce pain and fever and take proper rest to conserver energy
    • To stop the growth or kill the disease causing microbes: Take antibiotics (for bacterial disease) and pancillin (for bacterial disease)

    Principles of Preservations

    To prevent the spread of diseases we should adopt following pratices:-

    • Cover your Mouth and Nose with mask
    • Cleaning hands frequently
    • Maintain the safe distance from other people
    • Drink clean and treated water
    • Don't eat open or contaminated food
    • Manitain proper hyigienic habits
    • Avoid using others’ personal belongings

    What are antibiotics?

    Antibiotics are the chemicals used to block biochemical pathways important for bacteria. It is used for treating diseases caused by bacteria. Antibiotics do not work against viral infections as the viruses do not have their own biochemical mechanisms but depend upon that of the host.


    Q1: Define cell ?

    Answer: Cells are the basic units of organisms. Cells are made of a variety of chemical substances–proteins, carbo-hydrates, fats or lipids etc. Cell is a dynamic place .

    Q2: Complex reactions and repair goes on inside cells ? Is it true or false ?

    Answer: True

    Q3: Are Various specialised activities going inside our body are interconnected?

    Answer: Yes.

    Q4:Food is a necessity for cell and tissue functions. Is it true or false? ?

    Answer: True

    Q5: What do you understand from term health?

    Answer: Health means a state of physical, mental and social well-being.

    Q6:The health of all organisms will depend on their surroundings or their environment. Is it true ?

    Answer: yes,It is true.

    Q7: What is meaning of hygiene and sanitation ?

    Answer: Hygiene means purification of environment from micrograms causing diseases. Sanitation refers the steps or measure taken to ensure hygiene.

    Q8:What are 5 hygiene steps?

    Answer: 1. Protect the water source 2.Wash hands before preparing and taking food 3.Cover the food 4. Clean vegetables and fruits before use 5. Clean vegetables and fruits before use

    Q9: What are 5 sanitation steps ?

    Answer: 1.Treat and store water safely 2. Wash hands after defecation. 3. Control flies. 4. Avoid open defecation 5. Treatment of water

    Q10: Each of the organ systems has specific organs as its parts, and it has particular functions. Is it true or false?

    Answer: True

    Q11:The musculoskeletal system, which is made up of bones and muscles Is it true or false?

    Answer: true .

    Q12: What is symptoms of disease ?

    Answer: Symptoms just indicate that there is a disease. They do not indicate the exact type of disease.

    Q13: What is acute disease ?

    Answer: Acute diseases refer to a medical condition that occurs suddenly and lasts for a shorter period of time.

    Q14: What is chronic disease ?

    Answer: Chronic diseases develop slowly and last for a lifetime.

    Q15: What causes disease? ?

    Answer: There two main causes for diseases: Immediate cause: The organisms that enter our body and cause the disease are termed as an immediate cause. For example, virus, bacteria, protozoa etc. Contributory cause: The secondary factors which led these organisms enter our body are termed as a contributory cause. For example, dirty water, contaminated food, improper nourishment, poor standard of living, etc.

    Q16: What is pathogen ?

    Answer: Pathogens are external agents that cause diseases in other organisms. This pathogen includes harmful microbes or microorganism such as bacteria, virus, fungi or protozoa.

    Q17: What is parasites?

    Answer: A parasite is an organism that lives in another organism, called the host, and often harms it. It is dependent on its host for survival – it has to be in the host to live, grow and multiply.

    Q18: What is virus?

    Answer: A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism.It is not a cell.

    Q19: Protozoans are single-celled animals .Is it true?

    Answer: true

    Q20: What are diseases caused viruses ?

    Answer: Common examples of diseases caused by viruses are the common cold, influenza, dengue fever and AIDS

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