In its broad, ecological sense, “parasite” means an organism that feeds on the living tissues of another organism (called host) and causes harm to it without eating it entirely. An organism eating whole bodies of other organisms is called a predator, while an organism feeding on the tissues of another without causing harm to it is called a commensal.
In a narrower, medical sense, the term “parasite” is restricted to “animal” parasites, i.e. those belonging either to the motile unicellular eukaryotes unofficially called “protozoans” or to the multicellular animals (metazoans). For that reason, our parasitology course will not include viral, bacterial or fungal pathogens. Instead, because it aims at giving an idea about the diversity and evolution of animals, it will occasionally include metazoans that are not parasites. Some of them are interesting for the medical student as venomous animals, while others have no medical importance.
To understand the relationships between different parasites, the student needs to have a basic knowledge of taxonomy. A quick indicator: if you have no idea who Linnaeus was, you are poorly prepared for our course and should make an effort to fill the gaps in your background. Below are the major taxonomic ranks, from higher to lower level:
By convention, to each taxon is assigned a Latin name, although many have also names in English and other languages. For example, the scientific name of human as species is Homo sapiens; it belongs to genus Homo, family Hominidae, order Primates, class Mammalia, phylum Chordata, kingdom Animalia (Metazoa). Warning: we insist on the Latin names!
Our course will move from simpler to more complex organisms, so naturally we are beginning with unicellular (protozoan) parasites.
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Published in 2013
Copyright © Maya Markova