The accepted biological paradigm today, which has led to the development of the pleomorphism and germ theory, is Monomorphism (Gr. mónos: single + morphē: form).
This paradigm, developed by Louis Pasteur and other scientists, states that all microorganisms only have one possible form and do not have the ability to evolve into different types of organisms.
The germ theory followed, which states that specific diseases are caused by infection with specific microorganisms and are cured when the microorganisms have been destroyed.
This led to the development and widespread use of antibiotics, animal testing and many of the other atrocities of modern medicine.
Pleomorphism, the polar opposite of Monomorphism, was developed by scientists like Antoine Béchamp and Günther Enderlein and states that microorganisms have various life cycles and stages of development that can range between viruses, bacteria, yeast and fungi, depending on the type of microorganism and the environment it is presented with.
What is interesting is that pleomorphism and its proponents has been entirely written out of history books and encyclopedias and is not as much as mentioned, even for historical interest, in universities and training institutions.