Biology - Living as a Parasite
Living as a Parasite
Many of the pathogens  described above can also be called parasites
, because they live in or on other living things (the host) to obtain
their nutrients. Other kinds of organisms are parasitic too.
Parasites  can be classified in a number of ways. A common one is
according to their relationship with their host.
* ectoparasites  live on the surface of their host, e.g. in fur,
feathers and skin, and on roots, stems and leaves
* endoparasites  live in some part of the body of the host, e.g. in
gut or muscle, or inside leaves or other plant tissues
The host is usually affected by:
* the parasite's feeding activities - damage to tissues and blockage of
blood vessels, ducts and vascular tissue in plants
* the production of toxins - usually protein products of the parasite's
metabolic activities - resulting in fever, headache, nausea and
interference in the host's metabolic activities
* secondary infection - damaged tissues are exposed to other pathogens
_Advantages_ of living as a parasite are:
* a readily available food supply
* reduced competition
A _disadvantage_ is the exclusive dependence on the host. If the host
dies, the parasite dies.
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