The various degrees of parasitism are to a certain extent explained by the foregoing.
A flea living off of a dog's body is an example of parasitism.
I give my pets vaccinations and preventive medication to avoid various types of parasitism.
Parasitism occurs when one organism makes another organism its home and source of life.
Commensalism occurs in a few instances, but parasitism either external or internal is rare.
With parasitism, only one of the organisms involved is benefiting from the relationship.
Parasitism is almost always harmful to the host organism.