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.