ProtistsEukaryotic Organisms
Protists Protists: Eukaryotic
microorganisms in the Protist family.
Protists Typically have external
structures for motility. These include…
Flagella: Two central microtubules & 9 pairs of peripheral microtubules (a 9+2 arrangement) surrounded by a membrane.
Found in protozoa & algae, but only have one or two.
Cilia: Shorter & more numerous than flagella – have the same basic chemical composition & structure.
Beat together in a coordinated pattern along the surface to create a “wave”.
Protists Pseudopodia: “False
feet” that are temporary projections of cytoplasm associated with amoeboid movement.
Cytoplasmic Streaming: Movement that occurs along a surface via pseudopodia.
Classes of Protists Protists are divided into 3 groups:
Plant-like Protists aka Algae Fungus-like Protists Animal-like Protists
Plant-Like Protists Plant-Like Protists aka
Algae: Organisms with chloroplasts & carry on photosynthesis. Typically found in moist &
sunny environments. Most have a cell wall &
one or two flagella for motility.
Most reproduce via binary fission.
Includes dinoflagellates, diatoms, & euglenoid dinoflagellates.
Not associated with human disease.
Fungus-Like Protists Fungus-Like Protists: Known as
oomycota. Use sexual reproduction instead of
asexual. Spend most of their life cycle as
diploid cells, which are the result of a union of two haploid gametes during sexual reproduction.
Includes water molds & slime molds.
Water molds cause agriculturally relevant diseases.
Ex. Downy mildew on grapes, late blight on potatoes, etc.
Slime molds cause mildew & are sometimes classified as fungi.
NEITHER type cause disease in humans!
Saprophytes: Class that receives nutrients by decomposing dead organisms – slime molds fall into this category!
Animal-Like Protists Animal-Like Protists aka
Protozoa: Mostly unicellular organisms, possibly found in colonies.
Most are free living Many live in watery environments Can encyst (close itself in a cyst)
to preserve genetic material in unfavorable conditions.
Commensalism: The process of living in or on other organisms without harming them.
Protists can do this! Parasitism: The process of living
in or on another organism while taking nutrients from that organism – may or may not harm them.
Protists can do this too!
Protozoa There are 4 main classes of Protozoa, ALL
of which have members that can cause human disease… Mastigophorans Sarcodines Apicomplexans Ciliates
Mastigophorans Mastigophorans: Mainly
free-living, unicellular, flagellated organisms.
Some have symbiotic (helpful) relationships with plants & animals.
Some parasitize humans. Trypanosoma: Causes
African sleeping sickness. Leishmania: Causes skin
lesions or systemic disease with fever.
Giardia: Causes severe diarrhea.
Trichomonas: Causes vaginal inflammation. bb
Sarcodines Sarcodines: Protozoans that move & capture food
by forming pseudopodia. Feed mainly on other microorganisms, including other
protozoa & algae. Causes Ameobic dysentery.
Apicomplexans Apicomplexans:
Protozoans that are parasitic. Parasitic Immobile Typically have complex life
cycles requiring more than one host.
Plasmodium: The parasite that causes malaria.
Toxoplasma gondii: Infects domestic cats & can be passed on through handling of feces – causes damages to the unborn fetus of a pregnant human.
Ciliates Ciliates: The largest
group of protozoans, categorized by their large number of cilia. Have cilia over most of
their surfaces. Contractile Vacuole: A
well-developed organelle that regulates cell fluid.
Balantidium coli: The only ciliate to cause human disease – causes dysentary.