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.
Parasitism occurs when one organism makes another organism its home and source of life.
With parasitism, only one of the organisms involved is benefiting from the relationship.
I give my pets vaccinations and preventive medication to avoid various types of parasitism.
Commensalism occurs in a few instances, but parasitism either external or internal is rare.
Parasitism is almost always harmful to the host organism.