CBSE & NCERT Solutions Class 12 Biology Types of Pathogens

CBSE & NCERT Solutions Class 12 Biology Types of Pathogens

CBSE & NCERT Solutions Class 12 Biology Types of Pathogens

In this article, we have discussed  ‘Types of Pathogens‘, We have already discussed  what is Pathogens, Pathogen and diseases  in last post.

Types of pathogens: There are several types of pathogens affecting both animals including human beings and plants.


The vast majority of bacteria, which typically range between 1 and 5 micrometres in length, are harmless or beneficial to humans. However, a relatively small list of pathogenic bacteria can cause infectious diseases. One of the bacterial diseases with the highest disease burden is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally significant diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter, and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy.

Bacteria can often be killed by antibiotics, which are usually designed to destroy the cell wall. This expels the pathogen’s DNA, making it incapable of producing proteins and causing the bacteria to die. A class of bacteria without cell walls is mycoplasma (a cause of lung infections). A class of bacteria which must live within other cells (obligate intracellular parasitic) is chlamydia (genus), the world leader in causing sexually transmitted infection (STI).

Watch videos on the  same for better understanding and learning, Biology Class 12


Some of the diseases that are caused by viral pathogens include smallpox, influenza, mumps, measles, chickenpox, ebola, and rubella.

Pathogenic viruses are diseases mainly of the families of Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Polyomavirus, Rhabdoviridae, Togaviridae. Viruses typically range between 20 and 300 nanometers in length.

A study in detail about Viral with animated videos, Biology notes Class 12.


Fungi comprise a eukaryotic kingdom of microbes that are usually saprophytes (consume dead organisms) but can cause diseases in humans, animals, and plants. Fungi are the most common cause of diseases in crops and other plants. The typical fungal spore size is 1-40 micrometers in length.


According to the prion theory, prions are infectious pathogens that do not contain nucleic acids. These abnormally folded proteins are found characteristically in some diseases such as scrapie, bovine spongiform encephalopathy (mad cow disease) and Creutzfeldt–Jakob disease.

Other parasites

Some eukaryotic organisms, such as protists and helminths, cause diseases in humans.


Examples of algae acting as a mammalian pathogen are known as well, notably the disease protothecosis. Protothecosis is a disease found in dogs, cats, cattle, and humans caused by a type of green alga known as prototheca that lacks chlorophyll.

You can read more topics of Biology Class 12

Ecological Succession


For more class 12 online Biology notes of Class 12, NCERT solutions, CBSE guide , Exam pattern for board exams, log in with Takshila Learning.


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Tags: Pathogens, Types of Pathogens, Algal, Prionic, Viral, fungal, Bacteria.

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