NOTE: The current system of classification for eukaryotes has been changed. In 2005, based on new phylogenetic data the kingdom Protista was split into 5 supergroups. See Also: “Are You Still Teaching Taxonomy?”
Protists
Protists belong to the Kingdom Protista, which include mostly unicellular organisms that do not fit into the other kingdoms.
Characteristics of Protists
- mostly unicellular, some are multicellular (algae)
- can be heterotrophic or autotrophic
- most live in water (though some live in moist soil or even the human body)
- ALL are eukaryotic (have a nucleus)
- A protist is any organism that is not a plant, animal or fungus
Protista = the very first
Classification of Protists
- how they obtain nutrition
- how they move
Animallike Protists – also called protozoa (means “first animal”) – heterotrophs
Plantlike Protists – also called algae – autotrophs
Funguslike Protists – heterotrophs, decomposers, external digestion
Animal-like Protists: Protozoans
Four Phyla of Animal-like Protists – Classified by how they move
- Zooflagellates – flagella
- Sarcodines – extensions of cytoplasm (pseudopodia)
- Ciliates – cilia
- Sporozoans – do not move
Zooflagellates
move using one or two flagella
absorb food across membrane
Ex. Leishmania
Sarcodines
Ameba See Ameba Coloring Sheet
moves using pseudopodia ( “false feet” ), which are like extensions of the cytoplasm —ameboid movement
ingests food by surrounding and engulfing food (endocytosis), creating a food vacuole
reproducing by binary fission (mitosis)
contractile vacuole – removes excess water
can cause amebic dysentery in humans – diarrhea and stomach upset from drinking contaminated water
Other sarcodines: Foraminferans, Heliozoans
Video: Ameba Proteus
Ciliates
Paramecium (See Paramecium Coloring Sheet)
move using cilia
has two nuclei: macronucleus, micronucleus
food is gathered through the :mouth pore, moved into a gullet, forms a food vacuole
anal pore is used for removing waste
contractile vacuole removes excess water
exhibits avoidance behavior
reproduces asexually (binary fission) or sexually (conjugation)
outer membrane -pellicle- is rigid and paramecia are always the same shape, like a shoe
Sporozoans
do not move on their own
parasitic
Malaria is caused by a sporozoan (Plasmodium), which infects the liver and blood; transmitted by mosquitos