Protists
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 closeup!
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