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General Science · Class 9 · Chapter 5: Diseases, Causes and Prevention

8 min

Key points

Disease is defined as any disturbance in the structure and function of the body or mind
Diseases are classified into two main types: communicable (infectious) and non-communicable (non-infectious)
Communicable diseases are caused by pathogens like bacteria, viruses, fungi and parasites that spread from one person to another
Non-communicable diseases are not spread from person to person and include genetic disorders, deficiency diseases and degenerative diseases
Prevention is better than cure - vaccination, proper hygiene and balanced diet help prevent diseases
Common communicable diseases in Pakistan include tuberculosis, hepatitis, malaria, dengue fever and cholera
AIDS is caused by HIV virus which destroys the immune system making body vulnerable to infections
Deficiency diseases like rickets (Vitamin D), scurvy (Vitamin C) and beriberi (Vitamin B1) can be prevented by balanced diet
Personal hygiene, environmental sanitation and safe drinking water are essential for disease prevention

Definitions

Disease: Disease is any disturbance in the structure and function of the body or mind that results in physical or mental disorder
Communicable Disease: A disease that can be transmitted from one person to another through various means is called communicable disease
Pathogen: A disease-causing organism such as bacteria, virus, fungi or parasite is called a pathogen
Immunity: The ability of the body to resist and fight against diseases is called immunity
Vaccination: The process of introducing weakened or dead pathogens into the body to develop immunity against specific diseases is called vaccination

Worked example

Define disease. Classify diseases based on their causes and explain prevention methods for each type. (8 marks)

Disease is a condition in which one or more parts of the body are not functioning normally. Classification: (1) Infectious diseases - caused by pathogens like bacteria, viruses, fungi, and parasites. Prevention: vaccination, personal hygiene, sanitation, quarantine. (2) Non-infectious diseases - caused by genetic factors, lifestyle, environmental factors. Prevention: balanced diet, regular exercise, avoiding smoking and alcohol, regular health checkups.

Common mistakes

Students often confuse communicable with non-communicable diseases
Mixing up deficiency diseases with their respective vitamins
Writing incomplete definitions - always include both structure and function disturbance for disease definition
Forgetting to mention prevention methods when asked about disease prevention
Confusing pathogens - remember bacteria, viruses, fungi and parasites are all different types

Quick recap

Disease is abnormal functioning of body parts. Two main types: infectious (caused by pathogens - bacteria, viruses, fungi, parasites) and non-infectious (genetic, lifestyle, environmental causes). Prevention varies: infectious diseases prevented by hygiene, vaccination, sanitation; non-infectious by healthy lifestyle, balanced diet, regular exercise. Remember exact textbook definitions and specific prevention methods.

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