protists simplest eukaryotic cells eukaryotic characteristics nucleus and other complex organelles...
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Chapter 22Protists
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ProtistsSimplest eukaryotic cellsEukaryotic characteristics
Nucleus and other complex organelles
Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs”
More than one chromosomeProtozoansAlgaeFungiPlantsAnimals
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ProtistsVery diverse!Some may resemble plants, fungi, or animals
Lack complexity of “higher” organismsProtozoa—“first animal”
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ProtistsTaxonomy questionable & confusingTraditionally organized by motility
AmoeboidCilliateFlagellateSporozoans
Organize by evolutionary relationshipParabasalids & diplomonadsEuglenoids & kinetoplastidsRadiolarians & foraminiferansAlveolates & streamenophilesAmoebozoans
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Protozoal MovementFlagella—long
outer structures for movementUsually only a
fewCilia—short
outer structures for movementUsually many“Hair-like”
Pseudopod“False foot”
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Amoeboid ProtozoansAmoeba proteus
“Classic” amoebaPredatoryPseudopodsSee it move!
Entamoeba histolyticaFound in contaminated waterCauses diarrhea
50 million cases annually 100,000 deaths annually
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Amoeboid ProtozoansForaminiferans
Form shells Mostly calcium carbonate
Pseudopods protrude through holes (foramen) in shells
Over long spans, form chalk & limestone
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Amoeboid ProtozoansRadiolarians
Form shells Perforated Short silica rods
Numerous short, stiff pseudopods
Part of plankton
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Ciliate ProtozoansMost free-living heterotrophsFeed on algae, bacteria, each
other1/3 symbionts or parasites
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Ciliated ProtozoansParamecium
“Typical” ciliateCilia sweep water w/ food
into gulletMacronucleus &
micronucleus Micronucleus has full
genome but doesn’t transcribe
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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
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Ciliate ProtozoansStentor
Filter feederOne of largest single-
celled organisms Several millimeters!
Cilia around mouth create current
See it in action!
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Ciliate ProtozoansDidinium
Free-living predatorsTwo rings of ciliaMostly feed on
ParameciumToxin paralyzes prey’s
ciliaCan live in cysts for 10
yearsSee it hunting!Longer, but has great
close-up!
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Flagellate ProtozoansKinetoplastids
Mitochondria almost as long as bodyTrypanosoma brucei
African sleeping sicknessTransmitted by tsetse flyEnters spinal fluid & brain
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Flagellate ProtozoansEuglenoids
1/3 Heterotrophs2/3 PhotoautotrophsEye spot (stigma)
Detects lightEuglena
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Sporozoan ProtozoansNo structures for movementAll are parasiticComplex life cyclesMultiple hosts
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Sporozoan ProtozoansPlasmodium
Causes malariaMost widespread parasite of
humansDisease 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
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Sporozoan ProtozoansToxoplasma gondii
May be 60 million infections in US
“Fecal-oral” route Cat feces contaminating hands,
water, or utensilsMost infections have no
symptomsSome people show flu symptomsImmunosuppression increases
infection risk
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Sporozoan ProtozoansToxoplasma gondii (cont.)
Can cause serious disease in fetus if mother infected ONLY if is mother’s first
exposureCan affect host behavior
May be a cause of schizophrenia
Cats shed cysts for a few weeks after first infection
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