Question

What is the difference between an obligate parasite and a facultative parasite?

Answer 1

Definitions:

1. An organism that can not complete its life cycle without its host is called obligate parasite. They cannot live without host.
2. A facultative parasite is an organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. It is not completely dependent on host.

Differences:

1. Obligate Parasite	Facultative Parasite
   A parasitic organism that requires the host organism to complete its life cycle is known as an obligate parasite.	A parasitic organism that is able to complete and continue its life cycle even in the absence of the host is known as a facultative parasite.
   Life Cycle
   Obligate parasites have complex life cycles.	Facultative parasites have comparatively simple life cycles.
   Presence of the Host
   An obligate parasite can survive only in the presence of its host.	Facultative parasites can survive even in the absence of the host.
   Transmission through Host Organisms
   Obligate parasites travel directly from one host to another host.	Facultative parasites can pass important stages of their life cycle even without a host. They do not travel directly from one host to another.
   Free-living Nature
   Obligate parasites do not have free-living stages.	Facultative parasites are free-living when the host is absent.