Chapter 22Protists

ProtistsSimplest eukaryotic cellsEukaryotic characteristics

Nucleus and other complex organelles

Organelle—internal membrane-bound compartment that serves specialized functions. “Little organs”

More than one chromosomeProtozoansAlgaeFungiPlantsAnimals

ProtistsVery diverse!Some may resemble plants, fungi, or animals

Lack complexity of “higher” organismsProtozoa—“first animal”

ProtistsTaxonomy questionable & confusingTraditionally organized by motility

AmoeboidCilliateFlagellateSporozoans

Organize by evolutionary relationshipParabasalids & diplomonadsEuglenoids & kinetoplastidsRadiolarians & foraminiferansAlveolates & streamenophilesAmoebozoans

Protozoal MovementFlagella—long

outer structures for movementUsually only a

fewCilia—short

outer structures for movementUsually many“Hair-like”

Pseudopod“False foot”

Amoeboid ProtozoansAmoeba proteus

“Classic” amoebaPredatoryPseudopodsSee it move!

Entamoeba histolyticaFound in contaminated waterCauses diarrhea

50 million cases annually 100,000 deaths annually

Amoeboid ProtozoansForaminiferans

Form shells Mostly calcium carbonate

Pseudopods protrude through holes (foramen) in shells

Over long spans, form chalk & limestone

Amoeboid ProtozoansRadiolarians

Form shells Perforated Short silica rods

Numerous short, stiff pseudopods

Part of plankton

Ciliate ProtozoansMost free-living heterotrophsFeed on algae, bacteria, each

other1/3 symbionts or parasites

Ciliated ProtozoansParamecium

“Typical” ciliateCilia sweep water w/ food

into gulletMacronucleus &

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 ProtozoansStentor

Filter feederOne of largest single-

celled organisms Several millimeters!

Cilia around mouth create current

See it in action!

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!

Flagellate ProtozoansKinetoplastids

Mitochondria almost as long as bodyTrypanosoma brucei

African sleeping sicknessTransmitted by tsetse flyEnters spinal fluid & brain

Flagellate ProtozoansEuglenoids

1/3 Heterotrophs2/3 PhotoautotrophsEye spot (stigma)

Detects lightEuglena

Sporozoan ProtozoansNo structures for movementAll are parasiticComplex life cyclesMultiple hosts

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

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

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