Welcome to the Form 4 Biology revision notes for Somaliland schools. This guide covers the Human Health and Disease chapter, exploring pathogen types, body defense systems, and public health management.
Key Definitions in Human Health and Disease
What is a Disease?
A disease is any condition that impairs the normal functioning of the body or mind, causing physical or mental distress.
Pathogens
Pathogens are biological agents—such as bacteria, viruses, fungi, and protozoa—that cause infectious diseases in host organisms.
Major Types of Diseases
- Infectious (Communicable) Diseases: Spread from person to person (e.g., Malaria, Tuberculosis, Cholera).
- Non-Infectious (Non-Communicable) Diseases: Caused by genetics, lifestyle, or environment (e.g., Diabetes, Hypertension).
Body Defense Mechanisms
The human body uses barriers like skin and mucous membranes as a first line of defense, followed by white blood cells and the immune response to fight off foreign invaders.
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