Kingdom ProtistaBotany: Chapter 20 Notes

Evolution of EukaryotesProtist = “very first”Protists were the 1st Eukaryotic Cells to

evolve from Prokaryotic CellsFirst to have nuclei

1st Eukaryotes were zooflagellates ~ 2.2 bya

Protists! “very first” What are they?

There is no universal agreement amongst scientists as to what constitutes a protist

DiversityProtozoa – Animal-like protistsAlgae & Seaweeds – Plant-like

protistsSlime molds & water molds –

Fungus-like protistsRange in size

Microscopic to 250 ft. tall kelp!

Cellular OrganizationMost Unicellular

Some form colonies – an aggregation of loosely organized cells

Some are coenocytic – a multinucleated massSome are simple multicellular (without

specialized cells)

Ways of Obtaining NutrientsAutotrophs – Self nurished

Photosynthesize like plantsHeterotrophs

Absorb nutrients like fungiIngest food like animals

Can be a combination of these

DependencyMany are free livingSome form symbiotic relationships with other

organismsMutualism – partnership/both benefitCommensalism – 1 partner benefits/other is

neither helped nor harmedParasitism – 1 partner benefits/the other is

harmed

HabitatMost are aquatic (water dwelling)

Marine = saltwater environmentsFreshwater = ponds, lakes, streams

Some are terrestrial (land dwelling)Restricted to damp places = soil, bark, leaf

litter

ReproductionMostly AsexualSome Sexual

Syngamy – union of gametes

Mobility/LocomotionWaving CiliaLashing FlagellaFlexing individual cellsAmoeboid – use a “pseudopodia” = false

footCytoplasmic Streaming

By moving organelles around within the cytoplasm, they are able to change their shape, which allows them to move toward nutrients or away from toxins

Some use a combination of these

10 Phyla of Protists1. Euglenophyta – “Euglenoids”Unicellular2 flagellaAutotrophic – PhotosyntheticReproduce asexually by cell divisionDwell in FreshwaterHave an eyespot – helps perceive the

direction of light

10 Phyla of Protists2. Dinophyta– “Dinoflagellates”Unicellular, some colonial2 flagella Some Autotrophic – PhotosyntheticA part of marine plankton – base of the

aquatic food webForm Red Tides – produce a toxin that

attacks the nervous systems of fish, leading to massive fish kills; can become airborne

Dinos = “whirling”Mainly asexual

10 Phyla of Protists3. Oomycota– “water molds”Coenocytic mycelium

Mycelium is a body formgrows over a food sourcedigests it with enzymes that it secretesabsorbs the predigested nutrientsmade up of hyphae (one multinucleated cell)

2 flagella on zoosporesHeterotrophicContain cellulose and/or chitin in cell wallsCaused late blight – p. 389

10 Phyla of Protists4. Bacillariophyta– “Diatoms”Unicellular, some colonialMost nonmotile; some glide over secreted

slimeAutotrophic – PhotosyntheticContain silica in shellFreshwater & marineDiatomaceous earth p. 391

White Cliffs of Dover in Britain

10 Phyla of Protists5. Chrysophyta– “Golden Algae”Unicellular or Colonial2 flagella or noneAutotrophic – PhotosyntheticMay be covered by calcium carbonate or

silica scalesMake up part of nanoplankton

10 Phyla of Protists6. Phaeophyta– “Brown algae”All are Multicellular2 flagella on reproductive cellsAutotrophic – PhotosyntheticEx. Kelp

10 Phyla of Protists7. Rhodophyta– “Red Algae”Most multicellular; some

unicellularNonmotileAutotrophic – PhotosyntheticCan use floridean starch from

cell walls to make agar!

10 Phyla of Protists8. Chlorophyta– “Green Algae”Unicellular, colonial, siphonous “tubular” –

giant cells, or multicellularMost flagellated at some stage in life; some

nonmotileAutotrophic - Photosynthetic

10 Phyla of Protists9. Myxomycota– “plasmodial slime molds”Multinucleate plasmodium (changes shape as

it moves)Cytoplasmic streaming; flagellated or

amoeboid reproductive cellsHeterotrophicReproduce by spores

10 Phyla of Protists10. Dictyosteliomycota– “cellular slime

molds”Vegetative form; single cellReproductive form; multicellular slugAmoeboid (for single cells)Cytoplasmic Streaming (for multicellular)HeterotrophicTerrestrial

Why are Protists Considered Paraphyletic?