NCERT Solutions for Class 9 Science Why do we fall ill? – Disease and its causes

NCERT Solutions for Class 9 Science Why do we fall ill? – Disease and its causes

Here we will discuss 9th Class Science topic – ‘Disease and its causes’ from Why do we fall ill chapter?

Disease and its causes

The disease can be defined as a malfunctioning of the normal state of the living organism that disturbs or modifies the performance of the vital functions. There can be many reasons for diseases. Let us understand the sources of diseases.

Sources of disease

There are various factors, causes or sources. Let us discuss them in detail:-

• Intrinsic or internal factors– The diseases that occur within the human body recalled intrinsic factors. The factors which affect human health are as below:-

1. Malfunctioning of various body parts such as heart, kidney, liver etc.
2. Genetic disorder
3. Hormonal imbalance
4. Allergy-it means malfunctioning of the immune system of the body.

The diseases caused by internal factors are called metabolic diseases. Few examples are

• Cardiac failure (heart attack)
• Kidney failure
• Osteoporosis
• Myopia
• Cataract
• Sickle cell anaemia
• Cancer
• Arthritis
• Asthma
• Diabetes
• Haemophilia

Let us classify some disease of humans:

• Extrinsic or external factors-The disease-causing external agents which enter the human body by external force is known as extrinsic factors. The major factors which affect human health are

1. Environment pollution-various pollutants such as gases, particulate matter, industrial chemicals, heavy metals contribute to ailments
2. A microorganism which causes disease-microorganism such as a virus, bacteria, fungi, worms etc is transferred to the human body through air, water, food, physical contact etc.
3. Unbalance diet
4. Tobacco, alcohol and drugs etc leads to chronic diseases

Diseases caused by these factors are

• Pneumonia
• Leprosy
• Tetanus
• Diarrhoea
• Food poisoning

Watch and learn Diseases and its causes with animated videos Class 9 Science.  

Level of immediate causes

There are various immediate causes like virus infection is an immediate cause. Lack of good nourishment becomes the second cause. Poverty becomes an important cause; genetic difference also plays an important role in contributing to the causes of disease.

In the upcoming articles for 9 class science we will discuss types of diseases.

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