Protists

Simplest eukaryotic cells Eukaryotic characteristics Nucleus and other complex organelles Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs” More than one chromosome Protozoans Algae Fungi Plants Animals

Protists Very diverse! Some may resemble plants, fungi, or animals Lack complexity of “higher” organisms Protozoa—“first animal”

Protists Taxonomy questionable & confusing Traditionally organized by motility Amoeboid Cilliate Flagellate Sporozoans Organize by evolutionary relationship Parabasalids & diplomonads Euglenoids & kinetoplastids Radiolarians & foraminiferans Alveolates & streamenophiles Amoebozoans

Protozoal Movement Flagella—long outer structures for movement Usually only a few Cilia—short outer structures for movement Usually many “Hair-like” Pseudopod “False foot”

Amoeboid Protozoans Amoeba proteus “Classic” amoeba Predatory Pseudopods See it move! Entamoeba histolytica Found in contaminated water Causes diarrhea 50 million cases annually 100,000 deaths annually

Amoeboid Protozoans Foraminiferans Form shells Mostly calcium carbonate Pseudopods protrude through holes (foramen) in shells Over long spans, form chalk & limestone

Amoeboid Protozoans Radiolarians Form shells Perforated Short silica rods Numerous short, stiff pseudopods Part of plankton

Ciliate Protozoans Most free-living heterotrophs Feed on algae, bacteria, each other 1/3 symbionts or parasites

Ciliated Protozoans Paramecium “Typical” ciliate Cilia sweep water w/ food into gullet Macronucleus & micronucleus Micronucleus has full genome but doesn’t transcribe

Ciliate Protozoans “Sexual” & asexual reproduction (Fig 22.8) Physical contact, cytoplasmic fusion Micronucleus undergoes meiosis One 2n micronucleus  Four n micronuclei 3 of 4 mironuclei dissolve Remaining micronucleus undergoes mitosis, making 2 micronuclei Cells exchange one micronucleus Cells separate Original macronucleus dissolves Micronuclei divide (making 4) Two micronuclei develop into macronuclei Cell divides

Ciliate Protozoans Stentor Filter feeder One of largest single-celled organisms Several millimeters! Cilia around mouth create current See it in action!

Ciliate Protozoans Didinium Free-living predators Two rings of cilia Mostly feed on Paramecium Toxin paralyzes prey’s cilia Can live in cysts for 10 years See it hunting! Longer, but has great close- up! Longer, but has great close- up!

Flagellate Protozoans Kinetoplastids Mitochondria almost as long as body Trypanosoma brucei African sleeping sickness Transmitted by tsetse fly Enters spinal fluid & brain

Flagellate Protozoans Euglenoids 1/3 Heterotrophs 2/3 Photoautotrophs Eye spot (stigma) Detects light Euglena

Sporozoan Protozoans No structures for movement All are parasitic Complex life cycles Multiple hosts

Sporozoan Protozoans Plasmodium Causes malaria Most widespread parasite of humans Disease in 515 million people annually US population is 300 million 5 million infected with HIV annually Kills 1-3 million people annually 2.8 million AIDS deaths annually Transmitted by female Anopheles mosquito No vaccine

Sporozoan Protozoans Toxoplasma gondii May be 60 million infections in US “Fecal-oral” route Cat feces contaminating hands, water, or utensils Most infections have no symptoms Some people show flu symptoms Immunosuppression increases infection risk

Sporozoan Protozoans Toxoplasma gondii (cont.) Can cause serious disease in fetus if mother infected ONLY if is mother’s first exposure Can affect host behavior May be a cause of schizophrenia Cats shed cysts for a few weeks after first infection