Biology · Human Health and Diseases · NEET
NCERT states: 'A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man. Such disease-causing organisms are called pathogens.' So a pathogen is simply any organism that causes disease in a host. Learn this line word-for-word because NEET often tests it directly.
A pathogen can be either. 'Pathogen' is a broad word for ANY disease-causing organism, not one single type. Bacteria (like Salmonella typhi in typhoid), viruses (like Rhinoviruses in common cold), fungi, protozoans (like Plasmodium in malaria) and worms are all pathogens. Do not fix the word pathogen to only bacteria.
A parasite lives in or on a host and takes food from it. A pathogen is any organism that causes disease. NCERT says 'Most parasites are therefore pathogens as they cause harm to the host.' So a parasite that causes disease is a pathogen, but the word pathogen is wider and also covers viruses, which are not always called parasites.
No. NCERT says most parasites are pathogens, but the reverse is not stated as always true. Some organisms cause disease through toxins without living inside the host the way a classic parasite does. For NEET, remember the safe fact: 'Most parasites are pathogens' — do not flip it to 'all pathogens are parasites.'
Bacteria — Salmonella typhi (typhoid); Virus — Rhinoviruses (common cold); Fungi — Trichophyton (ringworm); Protozoan — Plasmodium (malaria); Helminth (worm) — Ascaris (ascariasis) and Wuchereria (elephantiasis). NEET loves match-the-column questions with these pairs, so memorise the organism-disease link.
NCERT explains: 'The pathogens can enter our body by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage.' In short, it enters, multiplies, and disturbs normal body functions. This is why not every exposure causes disease — our immunity often stops the pathogen first.
Which of the following sets of diseases is caused by bacteria?
Match List I with List II: A. Typhoid B. Leishmaniasis C. Ringworm D. Filariasis || I. Fungus II. Nematode III. Protozoa IV. Bacteria
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A pathogen is any disease-causing organism, such as a bacterium, virus, fungus, protozoan or worm.
Yes. NCERT lists viruses among pathogens because they cause diseases like the common cold and AIDS. When inside a host cell they multiply and cause damage, so they count as disease-causing organisms.
NCERT says we meet many infectious agents daily, but the immune system defends us, so only a few exposures lead to disease. This ability to fight pathogens is called immunity.
Yes. Helminths (worms) like Ascaris and Wuchereria are pathogenic to humans and cause ascariasis and elephantiasis respectively.
