Class 9
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
Created by Titas Mallick
Biology Teacher • M.Sc. Botany • B.Ed. • CTET (CBSE) • CISCE Examiner
A detailed classification of diseases, pathogens, and their modes of spread.
A disease is any condition that interferes with the normal functioning of the body. It is often characterized by specific signs and symptoms.
Diseases can be broadly classified into two categories:
Pathogens Pathogens are biological agents like bacteria, viruses, fungi, and protozoa that cause diseases. Communicable diseases are defined by their ability to spread these pathogens between hosts.
Diseases present since birth. They are caused by genetic abnormalities or metabolic disorders (e.g., Color blindness, Hemophilia, Down's syndrome).
Diseases that develop after birth. These are subdivided into:
Pathogens are biological agents that cause disease.
| Pathogen Type | Disease Examples | Mode of Transmission |
|---|---|---|
| Bacteria | Cholera, Tuberculosis, Typhoid | Contaminated food/water, Air droplets |
| Virus | Common cold, AIDS, Hepatitis, Polio | Air, Body fluids, Contaminated water |
| Protozoa | Malaria, Amoebic dysentery | Mosquito vector, Contaminated water |
| Fungi | Ringworm, Athlete’s foot | Direct contact, Infected towels |
| Helminths | Ascariasis, Taeniasis | Contaminated food |
Communicable diseases spread through various channels:
Vectors do not cause the disease themselves but carry the pathogen.
The housefly sits on garbage and fecal matter, picking up pathogens on its hairy legs and mouthparts. When it sits on uncovered food, it transfers these pathogens.
Different species of mosquitoes carry different pathogens:
They carry pathogens like Salmonella and E. coli on their bodies and transmit them to food in kitchens and storerooms.
Vector Control Eliminating stagnant water is the most effective way to control mosquitoes, as they require water to lay their eggs.
/Class-9/6_2_Diseases_and_Transmission.mdx