Protists Eukaryotic Organisms Protists p Protists Eukaryotic microorganisms

Protists Eukaryotic Organisms

Protists p Protists: Eukaryotic microorganisms in the Protist family.

Protists p Typically have external structures for motility. These include… n Flagella: Two central microtubules & 9 pairs of peripheral microtubules (a 9+2 arrangement) surrounded by a membrane. p n Found in protozoa & algae, but only have one or two. Cilia: Shorter & more numerous than flagella – have the same basic chemical composition & structure. p Beat together in a coordinated pattern along the surface to create a “wave”.

Protists n Pseudopodia: “False feet” that are temporary projections of cytoplasm associated with amoeboid movement. p Cytoplasmic Streaming: Movement that occurs along a surface via pseudopodia.

Classes of Protists p Protists are divided into 3 groups: n n n Plant-like Protists aka Algae Fungus-like Protists Animal-like Protists

Plant-Like Protists p Plant-Like Protists aka Algae: Organisms with chloroplasts & carry on photosynthesis. n n n 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 p Fungus-Like Protists: Known as oomycota. n n p 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. n Water molds cause agriculturally relevant diseases. p n n p 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 p Animal-Like Protists aka Protozoa: Mostly unicellular organisms, possibly found in colonies. n n n p Commensalism: The process of living in or on other organisms without harming them. n p Most are free living Many live in watery environments Can encyst (close itself in a cyst) to preserve genetic material in unfavorable conditions. 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. n Protists can do this too!

Protozoa p There are 4 main classes of Protozoa, ALL of which have members that can cause human disease… n n Mastigophorans Sarcodines Apicomplexans Ciliates

Mastigophorans p p p Mastigophorans: Mainly free-living, unicellular, flagellated organisms. Some have symbiotic (helpful) relationships with plants & animals. Some parasitize humans. n n Trypanosoma: Causes African sleeping sickness. Leishmania: Causes skin lesions or systemic disease with fever. Giardia: Causes severe diarrhea. Trichomonas: Causes vaginal inflammation. bb

Sarcodines p Sarcodines: Protozoans that move & capture food by forming pseudopodia. n n Feed mainly on other microorganisms, including other protozoa & algae. Causes Ameobic dysentery.

Apicomplexans p Apicomplexans: Protozoans that are parasitic. n n n p p 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 p Ciliates: The largest group of protozoans, categorized by their large number of cilia. n n p 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.