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Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly unicellular and microscopic.Many unicellular protists, particularly protozoans, are motile and can generate movement using flagella, cilia or pseudopods.
[4] [5] Although most protists are unicellular, there is a considerable range of multicellularity amongst them; some form colonies or multicellular structures visible to the naked eye. The term 'protist' refers to all eukaryotes that are not animals, plants or fungi, the three traditional eukaryotic kingdoms.
Invertebrates spread bacterial, viral and protozoan pathogens by two main mechanisms. Either via their bite, as in the case of malaria spread by mosquitoes, or via their faeces, as in the case of Chagas' Disease spread by Triatoma bugs or epidemic typhus spread by human body lice. Many invertebrates are responsible for transmitting diseases.
Its field of study therefore overlaps with the more traditional disciplines of phycology, mycology, and protozoology, just as protists embrace mostly unicellular organisms described as algae, some organisms regarded previously as primitive fungi, and protozoa ("animal" motile protists lacking chloroplasts).
The Ichthyosporea (or DRIP clade, or Mesomycetozoea) are a small group of Opisthokonta in Eukaryota (formerly protists), mostly parasites of fish and other animals.
Many protists have protective shells or tests, [139] usually made from calcium carbonate (chalk) or silica (glass). Protists are mostly single-celled and microscopic. Their shells are often tough mineralised forms that resist degradation, and can survive the death of the protist as a microfossil. Although protists are very small, they are ...
In some organisms, sexual reproduction has been shown to enhance the spread of parasitic genetic elements (e.g. yeast, filamentous fungi). [ 80 ] Bacterial conjugation is a form of genetic exchange that some sources describe as "sex", but technically is not a form of reproduction, even though it is a form of horizontal gene transfer .
At the same time, he raised the group to the level of a phylum containing two broad classes of microorganisms: Infusoria (mostly ciliates) and flagellates (flagellated protists and amoebae). The definition of Protozoa as a phylum or sub-kingdom composed of "unicellular animals" was adopted by the zoologist Otto Bütschli —celebrated at his ...