The pictures are shown for pathogens which are harmful to human body and 1st is virus 2nd is fungus 3rd is protozoa and 4th is bacteria.
Explanation: There are many pathogens that are harmful to people and they are harmful because they use the host machinery to replicate themselves and grow and also damages the host machinery and lyse the cell which in turn reduces the immunity of the host body and also make the host body prone to diseases leading to the early death of host or miserable life.
These pathogens are bacteria, protozoa, fungi, and viruses.
Virus - The viruses are considered as non-living or living depending upon whether they are outside the host cell or inside it as it they are outside they are nonliving and if inside they are living and have genetic material RNA or DNA and a protein coat called capsid.
Bacteria - The bacteria are also unicellular organisms which are prokaryotes and have a cell wall made up of peptidoglycan and can be divided in gram negative and gram-positive bacteria for example Xanthomonas.
Fungi - The fungi are multicellular organisms and have mycelia which is a thread-like structure in the form of a network called hyphae and they produce a different types of spores for their development.
Protozoa - They are microscopic and unicellular organisms and are eukaryotic in nature having complex structure and have complex metabolism and also have cilia for their movements.
So according to this 1st is virus 2nd is fungus 3rd is protozoa and 4th is bacteria.
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