Protist
| Protists |
|---|
Paramecium aurelia, a ciliate <tr><th bgcolor=khaki>Scientific classification <tr><td>
Heterokontophyta (heterokonts)
Cryptophyta (cryptomonads)
Pyrrhophyta (dinoflagellates)
Apicomplexa
Ciliophora (ciliates)
Euglenozoa
Metamonada
Foraminifera
Cercozoa
Amoebozoa
Choanozoa
Many others; classification varies </table> The Kingdom Protista or Protoctista is one of the commonly recognized biological kingdoms, including all the eukaryotes except for the plants, fungi, animals, and sometimes other groups which are treated in separate kingdoms. A few forms are multicellular, for instance the brown and red algae. The vast majority, though, comprise the single-celled organisms, and are typically only 0.01-0.5 mm in size, usually too small to be seen without a microscope. Protists are ubiquitous throughout aqueous environments and the soil, commonly surviving dry periods in the form of cysts; a few are important parasites. Traditionally protists have been divided into:
- Plant-like forms that have chloroplasts, the algae:
- Green algae,
- Red algae,
- Heterokont algae,
- Plus various other groups;
- Fungus-like forms:
- Animal-like forms, the protozoa, generally divided on the basis of morphology and locomotion into:
- Flagellates (e.g., Euglena),
- Amoeboids (e.g., Amoeba),
- Apicomplexa (e.g., Plasmodium),
- Ciliates (e.g., Paramecium)