Why Do We Fall Ill

Physics IX : Complete NCERT Exercise Solutions

Master Class 9 Science Chapter 13: Why Do We Fall Ill with detailed NCERT solutions. Understand the difference between health & disease, causes of diseases, infectious vs non-infectious diseases, and principles of prevention with important notes.

Question 13.1

State any two conditions essential for good health.

Answer & Explanation:

Two essential conditions for good health are:

• Balanced and nutritious diet
• Personal and environmental hygiene

These conditions help the body function efficiently and prevent diseases.

Question 13.2

State any two conditions essential for being free of disease.

Answer & Explanation:

Two conditions essential for being free of disease are:

• Proper sanitation and clean surroundings
• Immunity against infectious agents

Question 13.3

Are the answers to the above two questions the same or different? Why?

Answer & Explanation:

The answers are different because good health refers to overall physical, mental, and social well-being, while being disease-free only means the absence of illness.

A person may be free from disease but still not be in good health.

Question 13.4

List any three reasons why a person may suffer from poor health.

Answer & Explanation:

A person may suffer from poor health due to:

• Inadequate or unbalanced diet
• Poor sanitation and unhygienic conditions
• Mental stress and lack of physical exercise

Question 13.5

What are infectious diseases?

Answer & Explanation:

Infectious diseases are diseases that are caused by pathogens such as bacteria, viruses, fungi, or protozoa and can be transmitted from one person to another.

Question 13.6

What are non-infectious diseases?

Answer & Explanation:

Non-infectious diseases are diseases that do not spread from one person to another.

These are usually caused by factors such as nutritional deficiency, genetic disorders, or lifestyle habits.

Question 13.7

Name any two common air-borne diseases.

Answer & Explanation:

Two common air-borne diseases are:

• Tuberculosis
• Influenza

Question 13.8

What are vectors? Name any two diseases spread by vectors.

Answer & Explanation:

Vectors are organisms that transmit disease-causing pathogens from one host to another.

Diseases spread by vectors include:
• Malaria
• Dengue

Question 13.9

What is immunity?

Answer & Explanation:

Immunity is the ability of the body to resist or fight against disease-causing microorganisms by producing antibodies.

Question 13.10

Why is vaccination important?

Answer & Explanation:

Vaccination is important because it helps the body develop immunity against specific diseases.

It prevents the spread of infectious diseases and protects both individuals and the community.

📘 Exam Preparation Tip:

Clearly differentiate between being 'healthy' and 'disease-free'. Classify diseases as acute/chronic, infectious/non-infectious with examples. Understand the various causes of diseases and the general principles of prevention.