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““KingdomKingdom”” Protista Protista –– Tracing Tracing Early Eukaryotic EvolutionEarly Eukaryotic Evolution

• The eukaryotic cell• Where did the first eukaryotes come from?• The “kingdom” Protista• Review of some protists• Origins of multicellularity

The Eukaryotic cellThe Eukaryotic cell

Paramecium, a ciliated protozoan

This view is under Nomarski phase contrast

Eukaryotic cell componentsEukaryotic cell components•• Cell wall (optional)Cell wall (optional)•• Plasma membranePlasma membrane•• Cytoplasm containing organelles:Cytoplasm containing organelles:

** Nucleus Nucleus –– DNA in chromosomesDNA in chromosomes** Other membraneOther membrane--bound organellesbound organelles

•• MitochondriaMitochondria•• Chloroplasts (optional)Chloroplasts (optional)

** RibosomesRibosomes** Membrane systemMembrane system

•• Flagella (optional)Flagella (optional)

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Eukaryotic vs. prokaryotic cellsEukaryotic vs. prokaryotic cells

• Size* Prokaryotes ≤ 10 µm* Eukaryotes ≥ 10 µm

• Complexity* Prokaryotes – simple* Eukaryotes – complex

• Location of chromosomes* Prokaryotes – free in cytosol* Eukaryotes – within a nucleus

• Flagellar mechanisms differ

Bacteria & Archeaprotists, Fungi, Plants, Animals

Bacterium (prokaryote)

Animal (eukaryote)

Plant (eukaryote)

(Actual size relative to eukaryotes below)

Life Life CyclesCycles some fungi

effectively have (c)

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Evolution of First Eukaryote(s)Evolution of First Eukaryote(s)• Forces leading to eukaryote

* Increases in size* Increases in complexity

• Mechanisms* Infolding of cell membrane* Serial endosymbiosis of

membrane-bound organelles

ProtistaProtista as a single as a single ““kingdomkingdom””-- CharacteristicsCharacteristics

• Eukaryotic• “Simple” – single cells, simple colonies• Reproduction varies• Includes all Eukaryotes that are NOT plants,

fungi, or animals• Polyphyletic – a “wastebasket” category

protists are probably many protists are probably many KingdomsKingdoms

• All the Eukaryotic groups arranged phylogenetically

You do not need to know these, You do not need to know these, just give examplesjust give examples

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Protists:Protists:Functional gFunctional groupsroups

• Algae – photosynthetic• Protozoa – non photosynthetic, consumers• Fungus-like Protists – nonphotosynthetic,

hyphal

• Each group itself is polyphyletic

ProtozoaProtozoa• Animal-like• Heterotrophic by ingestion• Motile

* pseudopodia – amoebas* flagella – flagellates* cilia – ciliates

Pseudopodial movement in Pseudopodial movement in AmoebaAmoeba

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AmoebaAmoeba engulfing preyengulfing prey

Fig 28.26

FlagellatesFlagellates

Giardia

FlagellatesFlagellates Trypanosome – cause of African Sleeping Sickness (Tsetse fly)

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ParameciumCiliatesCiliates

Macronucleusw/ micronuclei

behind

Oral groove on surface

Site of cell “anus”

Food vacuoles

Cilia

Undulating membrane in groove (ciliary)

Contractile vacuoles

Food particles

Paramecium, a ciliated protozoan

AlgaeAlgae

• Plant-like• Photosynthetic autotrophs• Diverse morphology

* Single cells, filaments, colonies, thalli

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Green AlgaeGreen Algae

Spirogyra

(with friend)

RedRed AlgaeAlgae

Bonnemaisonia

Brown AlgaeBrown Algae

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Other Other ““AlgaeAlgae””Euglena Diatoms

GoldenDinoflagellate

RED TIDERED TIDE

FungusFungus--like Protistalike Protista

• ± Tubular• Hetertrophic by absorption• Polyphyletic

* Slime molds* Water molds

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PlasmodialPlasmodial slime moldsslime molds

Slime stage

Sporangia

Cellular slime moldsCellular slime molds

See Fig 28.30

““EggEgg”” water water moldsmolds

hyphae

Motile, asexual spores

Sexual cycle

Fig 28.16

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Ecology of the ProtistsEcology of the Protists

• Though small, play major (keystone?) roles* 65 % of earth’s net primary production

(phytoplankton)* Microfeeders of bacteria, other protists* Food for larger plankton & animals* Habitats for other organisms* Decomposers* Parasites of plants and animals

Multicellularity Multicellularity --coloniescolonies

•• All cells the sameAll cells the same•• No differentiation in functionNo differentiation in function•• Cooperation Cooperation ☺☺

** VolvoxVolvox** Filaments are a kind of colonyFilaments are a kind of colony

•• May provide May provide ““buoyancybuoyancy””

Multicellularity Multicellularity --complex bodiescomplex bodies

•• Differentiation of tissues, organsDifferentiation of tissues, organs** Allows larger bodiesAllows larger bodies** Division of laborDivision of labor** Requires more complex developmentRequires more complex development

•• Several timesSeveral times** Seaweeds Seaweeds –– 3 lines, one to plants3 lines, one to plants** FungiFungi** AnimalsAnimals

Kelp forest