Phyla Platyhelminthes and Nematoda are characterized by having a rather large number of species which are parasitic. Parasites are organisms that live in close association with another organism, called a host, and gain food to the detriment of the host. Some parasites, called ectoparasites, live on the outer skin of the host. Other parasites, called endoparasites, live amongst the internal organs of the host.
Flukes and tapeworms, members of Phylum Platyhelminthes are all parasites. Though only a few are parasitic to humans, many of the others are parasitic to the livestock upon which humans depend. Because of this, much scientific research has gone into studying their lifecycles in an effort to protect humans and our resources.
Nematodes, like bacteria, live in a wide variety of environments. Most are harmless, but a few are parasitic to humans and our livestock. Nematodes are able to survive in some many hostile environments due to their tough cuticle. This same cuticle can make it rather difficult to get a nematode out of a person once it is in. In most cases the only cure for a nematode is to give the infected person a dose of poison which will hopefully be strong enough to kill the worm without killed the host. |
2002 McGraw-Hill Higher Education