botany: chapter 20 notes. evolution of eukaryotes protist = “very first” protists were the 1 st...
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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?
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